Ph. D. THESIS 2009

“BABES-BOLYAI” UNIVERSITY CLUJ-NAPOCA
FACULTY OF CHEMISTRY AND CHEMICAL ENGINEERING
ORGANIC CHEMISTRY DEPARTMENT
Ph. D. THESIS
Contributions to the Synthesis and Structural Analysis of
Some Bicyclic Compounds and to the Fabrication of 3D
Metallic Micro – and nanostructures by Laser Induced
Photochemistry
Ph.D. Thesis Abstract
Ph. D. Student
Nicoleta Ioana TOŞA
Scientific Advisor
Prof. Dr. Ion GROSU
CLUJ-NAPOCA
2009

JURY
“BABES-BOLYAI” UNIVERSITY CLUJ-NAPOCA
FACULTY OF CHEMISTRY AND CHEMICAL ENGINEERING
ORGANIC CHEMISTRY DEPARTMENT
Ph. D. THESIS
Contributions to the Synthesis and Structural Analysis of
Some Bicyclic Compounds and to the Fabrication of 3D
Metallic Micro – and nanostructures by Laser Induced
Photochemistry
Ph.D. Thesis Abstract
Ph. D. Student
Nicoleta Ioana TOŞA
President Prof. Dr. Ioan Silaghi-Dumitrescu, Dean of the
Faculty of Chemistry and Chemical Engineering,
Cluj-Napoca
Scientific advisor Prof. Dr. Ion Grosu, Faculty of Chemistry and
Chemical Engineering, Cluj-Napoca
Reviewers Prof. Dr. Ionel Mangalagiu, University “Al.I. Cuza”,
Iasi
D. R. Dr. Patrice Baldeck, University “Joseph
Fourier”, Grenoble, France
Prof. Dr. Simion Astilean, University “Babes-
Bolyai”, Cluj-Napoca
Defense on 7 th October 2009
1

General Introduction
OUTLINE
Part A
Synthesis and Structural Analysis of Some
Bicyclo[3.3.1]nonane Derivatives
1. Bicyclo[3.3.1]nonane-3,7-dione 11
1.1. Introduction 11
1.1.2. Synthesis of bicyclo[3.3.1]nonane-3,7-dione 11
1.3. Structural aspects in solution 13
1.3.1. NMR investigations 13
1.3.1.1. Tetramethyl 3, 7-dihydroxybicyclo[3.3.1] nona-2, 6-diene
-2, 4, 6, 8-tetracarboxylate 13
1.3.1.1. Bicyclo[3.3.1]nonane-3,7-dione 17
1.3.2. FT-IR investigation of tetramethyl 3, 7-dihydroxybicyclo[3.3.1] nona-
2, 6-diene-2, 4, 6, 8-tetracarboxylate 20
1.4. Solid state investigations 23
1.4.1. FT-IR and Raman investigations 23
1.4.1.1. Tetramethyl 3, 7-dihydroxybicyclo[3.3.1] nona-2, 6-diene-
2,4,6,8-tetracarboxylate 24
1.4.1.2. Bicyclo[3.3.1]nonane-3,7-dione 30
1.4.2. Mass spectrometry study of bicyclo[3.3.1]nonane-3,7-dione 35
1.4.3. Single crystal X-ray diffraction investigations 38
1.4.3.1. Tetramethyl 3,7-dihydroxybicyclo [3.3.1] nona-2,6-
diene-2,4,6,8-tetracarboxylate 38
1.4.3.2. Bicyclo[3.3.1]nonane-3,7-dione 40
1.5. Molecular modeling: structure and IR spectra 42
1.5.1. Tetramethyl 3,7-dihydroxybicyclo[3.3.1]nona-2,6-diene-
2,4,6,8-tetracarboxylate structure 42
1.5.2. Bicyclo[3.3.1]nonane-3,7-dione 48
1.6. Attempts of synthesis of spiro-bis(dioxane) bicyclic compounds type 50
1.6.1. Synthesis of spiro-monodioxane compounds 50
1.6.2. NMR spectra in solution 51
1.6.3. Mass spectra of monospirane 56
1.6.4. FT-IR measurements 60
2. Bicyclo[3.3.1]nonane-3,7-dione dioxime
62
2.1. Introduction 62
2.2. Synthesis of syn and anti isomers 63
2.3. Investigations in solution 66
2.3.1. NMR spectra of syn and anti isomers 66
2.3.2. NMR study of kinetics of the synanti isomerisation 70
2.3.3. Chiral HPLC studies 74
2.3.3.1. Investigation of a mixture of syn and anti isomers 74
2.3.3.2. Investigation of the isolated anti isomer 76
2.3.4. FT-IR study 77
2.4. Investigation of bicyclo[3.3.1]nonane-3,7-dione dioxime in solid state 80
2.4.1. FT-IR 80
2.4.2. Single crystal X-ray diffraction 83
2

2.5. Mass spectrometry of bicyclo[3.3.1]nonane-3,7-dione dioxime 87
2.6. Molecular modeling for the supramolecular architectures of syn and anti isomer 90
2. Conclusions of the part A
96
3. Experimental part
97
4.1. General experimental 97
4.2. Synthesis and characterization of compounds 100
References 101
Part B
Fabricatio n o f 3 D Metallic Micro - an d n an o stru ctu res by
Laser In d u ced Ph o to ch em istry
1. Principle of the micro/nanostructuration by two-photon induced
photochemistry. State of the art 1 4 6
2. Experimental part: fabrication and characterization 159
2.1. Sample conditioning 159
2 1.1.Composition 159
2.1.2. Preparation 161
2.1.3. Thin film deposition 163
2.1.3.1 The key stages in spin coating 163
2.1.3.2.Polyimide underlayer spin-coating 163
2.1.4. Washing process 166
2.2. The metallic fabrication process 168
2.2.1. Experimental set-up 168
2.2.2. Laser source 168
2.2.3. The control of the microscope motorized stage 169
2.3. Characterization of the metallic structures 170
2.3.1. Optical and spectroscopical microscopy 171
2.3.2. Scanning electronic microscopy 171
2.3.3. Atomic force microscopy 172
3. Optimization of silver micro/nanostructures fabrication
175
3.1.Introduction 175
3.2. The approach of silver photographic process 177
3.2.1. The principle of the silver photographic process 177
3.2.2. Our chemical system 179
3.3. TPA fabrication of silver wires 180
3.3.1. Processing parameters 180
3.3.2. Thermal effect limitation 181
3.4. Chemical nature of the silver deposition 183
3.5. TPA approach induced by silver nanoparticles 185
3.5.1. General mechanism 185
3.5.2. The reduction mechanism by thermal effect 185
3.5.3. Our chemical system 187
3.6. TPA fabrication of 2D and 3D silvermicro/nanostructures 188
3

3.6.1. Dots 188
3.6.2. 3D structures 192
3.6.2.1. Fabrication 192
3.6.2.2. Silver porosity due to the corosion 196
3.6.2.3. Electroless plating process 199
4. Optimization of gold micro/nanostructures fabrication
207
4.1. Introduction 207
4.2. UV-Vis investigation 208
4.3. The gold structures fabrication process 211
4.3.1. PSS- matrix for gold microfabrication 211
4.3.2. Double-line effect in thin PSS matrix 214
4.3.3. The influence of the operating parameters 219
4.3.3.1. The laser power 219
4.3.3.2. The substrate 222
4.3.3.2.1. Glass 222
4.3.3.2.2. Polyimide underlayered glass 223
4.3.3.3. Gold salt concentration 224
4.4. The thermal effect 227
4.4.1. Theoretical model 230
4.5 The overcoming of the thermal effect 232
4.5.1 Nanodots 230
4.5.2. Single wires 234
4.5.3. 3D structures 237
5. Optical properties of the metallic structures
239
5.1. Introduction 239
5.2. Diffraction properties 239
5.3. 3D photonic crystals 243
6. Conclusions of the part B
247
References 248
Keywords: intra- and intermolecular H-bonds, keto-enol tautomerism, syn and anti
stereoisomers, self-assembly, supramolecular chemistry, laser induced photochemistry,
two-photon absorption, thermal effect, 3D structures.
4

General Introduction
The chemistry of the bicyclic compounds and their derivatives is a
challenging domain. Particularly, bicyclo[3.3.1]nonane derivatives represent
important intermediates in the synthetic routes to alkenes containing
piramidalized carbon atoms, to derivatives of potential interest for the treatment
of Alzheimer’s disease as well as to derivatives of dioximes type which can
form self-assembled supramolecular structures through intermolecular
hydrogen bonds. The fabrication of metallic structures based on two-photon
absorption represents a new and promising domain due to the innovative
technique and to the multiple applications in microelectronics, biosensing and
spectral filtering devices.
This work reflects my activity accomplished within the framework of
two powerful research groups. Even if the subjects developed seem to be
disconnected, at the first sight, they belong to the field of the chemical reactions
assisted by the electromagnetic radiation. The aim of this thesis is to bring a
contribution within these fields.
The thesis is structured in two parts. The first part – Part A – refers to
the contributions to the synthesis of some bicyclo[3.3.1]nonane derivatives and
their structural analysis. The second part –Part B – presents innovative issues
for the engineering of 3D metallic micro- and nanostructures by laser induced
photochemistry. The second part presents also some aspects concerning optical
and spectroscopic characteristics of such metallic structures.
5

Part A: Synthesis and Structural Analysis of Some
Bicyclo[3.3.1]nonane Derivatives
1. Bicyclo[3.3.1]nonane-3,7-dione
Due to its special characteristics, which involve a preorganisation of the
molecular structure, bicyclo[3.3.1]nonane-3,7-dione 2 is of interest for the
synthesis of some bicyclic derivatives and thus, for macrocycles as a
supramolecular connector. Thus, a series of macrocyclic compounds containing
bicyclic units have been already obtained [1]. The properties of synthesized
macrocyclic compounds are significantly dependent on the spatial arrangement
of the synthon at molecular level.
In this respect we focused on the synthesis and structural aspects of compound
2, as well as on the structural analysis of its precursor, namely tetramethyl 3,7dihydroxybicyclo[3.3.1]
nona-2,6-diene-2,4,6,8-tetracarboxylate 1.
1 .2 . Sy n th esis o f bicy clo [3 .3 .1 ]n o n an e -3 ,7 -d io n e
Sy n t h esis o f b icy clo [3 .3 .1 ]n o n a n e -3 ,7 -d io n e st a r in g fr o m
t etr a m eth y l 3 ,7 -d ih y d r o xy b icy clo [3 .3 .1 ] n o n a -2 ,6 -d ien e -
2 ,4 ,6 ,8 -t e t r a ca r b o xy la t e 1 r ep r esen t ed a ch a llen ge d u e t o t h e
h a r d co n d it io n s o f r e a ct io n . Th e lit er a t u r e d a t a in d ica t e a
t wo -st ep s h y d r o ly sis-d eca r b o xy la t io n r o u t e, in vo lv in g
gen er a t io n o f b icy clic β -d ik etotetr a est er s a s in t er m ed ia r , a n d
t h en it s co n v er sio n in t o b icy clic d ik eton e m a in ly u sin g
a cid ic ca t a ly st s (e.g. h y d r o ch lo r ic a cid [2 ] o r a m ixt u r e o f
h y d r o ch lo r ic a cid a n d a cet ic a cid [3 ]).
In t h e ligh t o f t h e se a sp ect s we p r o p o se a st r a igh t fo r wa r d
co n ver sio n o f co m p o u n d 1 in t o co m p o u n d 2 sim p ly h ea t in g
a t h igh t em p er a t u r e a m ixt u r e o f t etr a est er 1 a n d a sm a ll
a m o u n t o f wa t er , p la ce d in t o in a sea led b o r o silica t e t u b e.
H 3COOC
HO
H 3COOC
COOCH 3
(a)
OH
O
(b) H2O, K-10
MW irrad.
1
COOCH3 2
6
H 2O
O

Sch e m e 1 . Th e co n ve r sio n o f 1 in t o 2 via h y d r o ly sisd
e ca r b o xy la tio n r o u t e .
The reaction underwent with the complete hydrolysis and decarboxylation
of all four ester groups. The total transformation is supported by TLC
chromatography as well as by the melting point of the crude product, which is
0.5°C smaller than that of the pure compound 2.We have to highlight the
novelty of this method through its simplicity (one-step), high efficiency (yields
over 96%) and because it requires no catalyst.
We also developed an alternative way to the above proposed method. Thus,
compound 1 was deposited on a solid support, placed into a teflon sealed tube
and irradiated in microwave field.
The results of these two methods can be summarized in Table 1:
Table 1 Comparisson between classic and microwave irradiation methods
Method Yield (%) M.p.
7
(ºC)
classic Method (a) 98 250
microwave
irrad.
Method (b) 90 249-250
The advantages of these syntheses over the previous ones lie in the
direct transformation of 1 into 2, as well as in the significantly increased yields,
due to the absence of the acidic conditions and to the facile work-up procedure.
1.3. Structural aspects in solution
The bicyclic tetraester 1 and the bicyclic diketone 2 were both investigated
by NMR spectroscopy in solution at room temperature in order to establish
their structure and thereby to evidence the complete hydrolysis-decarboxylation
of the precursor 1. This may present as most of β-ketoesters two tautomeric
forms, enol and ketone, in equilibrium.
Keto-enol tautomerization of compound 1 (Scheme 2) in CDCl3 solution
has been investigated by NMR spectroscopy.

H 3C
H 3C
O
O
O
C
C
O
O
1a
O
O
C
C
O
O
O
CH 3
CH 3
8
H 3C
H
O
O
O
C
C
H 3C
O
O
O
O
CH 3
Scheme 2. The keto-enol tautomeric equilibrium
In Figure 1 is presented a fragment of the 1 H-NMR spectrum (CDCl3, 500
MHz) of compound 1. The 1 H NMR spectrum of 1 consists of 2H triplet at δ=
1.93(J=3.0 Hz), another 2H triplet at δ= 3.22(J=3.0 Hz), singlets at δ= 3.29
(2H), δ= 3.76 (6H), δ= 3.83 (6H), and δ= 12.33 (2H) ppm.
Figu re 1 . Th e 1
H-NMR sp e ct r u m (CDCl , 5 0 0 MHz, fr a gm e n t )
3
o f co m p o u n d 1
The fact that the hydrogen atoms at 1-C/5-C and those at 9-C give rise to
triplets indicate that the bridgehead hydrogen atoms are equivalent and
establishes the C2 symmetry of the molecule. Also, the broadening of both
peaks suggests a weak coupling between the protons at 2-C /6-C and those at 9-
C, which are connected in W path [7].
1b
C
C
O
O
O
H
CH 3

Figu re 1 . Th e
co m p o u n d 1
1
H-NMR sp ectr u m (CDCl , 5 0 0 MHz, fr a gm en t) o f
3
The signal at δ= 3.29 from hydrogen atoms at 2-C/6-C is a singlet. As time
as the dihedral angle between these protons and those at 1-C/5-C is close to 90 0
[8], the vicinal coupling between them is not possible. Also, this is possible to
have a singlet if the ester groups located in position 2-C/6-C have the exo
configuration, and the conformations of the two six-membered rings are closed
to the half-chair [9], expected for a cyclohexene derivative.
The two singlets at δ= 3.76 and δ= 3.83 correspond to the protons of ester
methyl groups at 15-C/17-C and 14-C/16-C, respectively. The small shift
appears because the ester groups are not equivalent, those located at position 4-
C/8-C being involved in intramolecular hydrogen bonding.
Compound 1 exhibits two possible enol forms, both of them involving the
formation of hydrogen bonds (Scheme 3).
CH3
H
O
O
O
C
C
O
O
CH 3
1a
O
O
CH 3
C
C
O
O
O
H
CH 3
9
CH 3
H
O
O
O
CH 3
Scheme 3. Theoretical enol forms for compound 1
C
C
O
O
1b
O
O
C
C
O
O
O
CH 3
H
CH 3

The two forms are in equilibrium and because the equilibration is fast, the
NMR spectrum does not show different signals for the two isomers. The spectra
exhibit unique signals at mean values of chemical shifts.
The strong deshielded signal at δ= 12.32 ppm indicate the presence of the enol
form and can be assigned to the hydrogen atom involved in the formation of
intramolecular hydrogen bonds. The enol structure is supported by the
interactions (observed in HMQC spectrum) of the signal belonging to the
carbon atoms at positions 3 and 7 and the signal pertaining to the enol hydrogen
atom.
The 13 C NMR spectrum is presented in Figure 2. The presence of two very
deshielded signals (Figure 2) located at δ= 171.77ppm and δ= 170.76 ppm,
characteristic for the C=O of an ester group, as well as the absence of a C=O,
characteristic for ketone (close to 208 ppm) come to support the bis(enol)
structure, predicted by the 1 H NMR data.
The spectrum also shows two peaks at δ= 168.03 ppm and δ= 101.99 ppm,
characteristic for quaternary atoms involved in carbon-carbon double bonds,
ascribed to the 3-C/7-C and 4-C/8-C, respectively.
Figure 2. The 13 C-NMR (spectrum CDCl 3, 125 MHz) of compound 1
The 13 C NMR data combined with the evidences of the hydrogen bonds from
1
H-NMR spectrum reveal no keto form but exclusively a bis(enol) form,
stabilized by intermolecular hydrogen bonds, for compound 1.
The 1
H-NMR and 13
C-NMR spectra of compound 2 are presented in Figure 3
and Figure 4 and present some characteristic patterns observed at compound 1.
10

Figure 3. The 1 H-NMR spectrum (CDCl 3, 500 MHz, fragment) of compound 2
Thus, the 2H multiplet at resonance δ= 2.20 ppm(J=3.0 Hz) is ascribed to the
protons located at 9-C, whereas the most deshielded 2H multiplet at δ= 2.86
ppm (J=3.0 Hz) corresponds to the bridgehead protons belonging to 1-C/5-C.
The bridge protons 9-H2 are splitted by the 1-H and 5-H protons due to a vicinal
coupling. The broadening of these peaks suggests an additional weak coupling
in W path between the equatorial protons at 2,4,6,8-C and those at 9-C, whereas
the protons 1-H and 5-H are coupled with the axial protons at 2,4,6,8-C. These
two triplets suggest also the equivalence of the bridgehead protons and the C2
symmetry of the molecule.
The 4H doublet at δ= 2.41 ppm is attributed to the equatorial protons at
2,4,6,8-C , which are connected with the corresponding axial protons through
an AB geminal coupling (J=15.5 Hz). The lack of supplementary splitting of
the doublet indicates that an equatorial-equatorial vicinal coupling with the
bridgehead protons at 1-C/5-C is not possible because a dihedral angle close to
90. The axial protons at 2,4,6,8-C are more deshielded and appear as a
doublet of doublets at δ= 2.58 ppm due to the both splitting originating from
the AB geminal coupling with the equatorial protons and the vicinal coupling
with the protons 1-H/5-H.
The most deshielded signal in the spectrum (Figure 4) has low intensity and is
situated at δ= 208.59 ppm, very close to the chemical shift of the carbonyl in
the cyclohexanone.
11

Figu re 4 . Th e 13
C-NMR APT (CDCl , 1 2 5 MHz) sp e ct r u m o f
3
co m p o u n d 2
The bridgehead tertiary carbon atoms at 1-C/5-C are located in the 13 C-
NMR APT spectrum at resonance δ= 32.64 ppm.
In conclusion, the missing of a deshielded signal pertaining to the enol
protons in 1 H NMR spectrum, as well as the presence of a highly deshielded
signal at δ= 208.59 ppm in the 13 C NMR spectrum, characteristic to the
quaternary carbonyl atom, suggests the preference for the ketone form in the
case of compound 2. Also, the conversion of 1 to 2 and the common elements
of the NMR spectra of these compound are stated to confirm the presence of
the bicyclo[3.3.1]nonane skeleton into the structure of compound 2.
1 .3 .2 . FT-IR in ve stigatio n o f tetram eth y l 3 , 7 -
d ih y d ro xy bicy clo [3 .3 .1 ] n o n a -2 , 6 -d ien e -2 , 4 , 6 , 8 -
tetracarbo xy late
One of the most suitable tools to investigate the nature of the hydrogen bonds
in the bicyclic tetraester 1 is the FT-IR spectroscopy in solution. The
experimental study consisted of the IR spectra registration in solution for
compound 1 [10] in order to investigate the behavior of substance in terms of
maintaining the hydrogen bonds and the way in which specific peaks of the
form enol changes with solvent polarity.
Theoretical spectra of conf_A and conf_B have been modeled to be compared
with experimental spectrum in order to identify which is the preferred
12

conformation of the enol form, stabilized by hydrogen bonds (the best
agreement between spectra). For theoretical modeling of IR spectra of the enol
form were considered two tautomeric structures, namely conf_A, where the Hbonds
are established between the enol OH group and the oxygen belonging to
the methoxy fragment, and conf-B, where the H-bonds are established between
the enol OH group and the carbonyl oxygen of the ester group. Both structures
are presented in Figure 5. Therefore, for the sake of clarity we will still use
these names in order to denote the corresponding structures during this study.
a b
Figure 5. Two possible conformations of the enol form: a) conf_A; b) conf_B.
In Figure 6 are presented comparatively the experimental spectrum in solution
and the theoretical spectra for both conformations modeled for compound 1.
Absorbance [a.u.]
100
80
60
40
20
0
1628
1663
1600 1650 1700 1750 1800 1850
Wavenumber [cm -1 ]
1739
13
Conf_A
Conf_B
Exp
Figure 6. Theoretical and experimental IR spectra (1600 – 1800 cm-1)
in the C=O and C=C stretching region, using dichloromethane as solvent.
The presence of carbon-carbon double bond peak around 1630 cm -1
associated with the carbon-oxygen double bond peak around 1660 cm -1 ,
characteristic to the carbonyl stretching vibration in enols, comes to support the
preference of compound 1 for enol form. The partial unagreement between the
theoretical and experimental spectra originates from the dimension of the basis

set used , the anarmonicities that occurs and the fact that the molecule is
considered as being isolated.
1.4. Solid state investigations
The experimental FT-IR and FT-Raman spectra of the 1 are presented
in Figure 7, in order to draw conclusions about the vibrational behaviour of
compound 1.
Absorbance (a.u.)
0.7
0.6
0.5
0.4
0.3
0.2
0.1
(2)
(1)
706
839
757
809
840
923
947
992
1031
FT-IR (1)
FT-Raman (2)
1171
1101
1168
1195
1278
1311
1353
1438
1447
0.0
600 800 1000 1200 1400 1600 1800
Wavenumber (cm-1 )
1241
1256
1357
1446
1630
1627
1660
1729
1740
1661
1734
1743
14
Absorbance (a.u.)
0.20
0.15
0.10
0.05
0.00
839
2844
757
2844
2871
2870
2947
2959
2938
2956
454
368
233
3003
3029
3005
3025
3050
(2)
2900 3000 3100
Wavenumber (cm -1 )
a b
Figure 7. a) FT-IR (ATR) and FT-Raman spectra of the compound 1; b) The
corresponding high wavenumber spectral regions. Excitation: 1064 nm, 380 mW
Th e e xp er im en t a l FT-IR a n d FT-Ra m a n sp ect r a o f t h e
co m p o u n d 2 a r e p r e se n t ed in Figu r e 8 , in o r d er t o est a b lish
co m m o n a s well a s d iffer en t elem en t s a b o u t t h e v ib r a t io n a l
b eh a vio u r o f 2 r e la t iv ely t o co m p o u n d 1 . Due to the molecular
symmetry, a considerable number of frequency lines are missing both from the
IR and Raman spectra (Figure 8), while the other lines have very small
intensity. Both absorption spectra are simpler than in the case of structure 1.
(1)

Absorbance (a.u.)
1.0
0.8
0.6
0.4
0.2
0.0
706
708
792
816
938
1075
1092
872
979
1017
1093
1101
1231
1239
1251
1301
1337
1423
FT-IR (1)
FT-Raman (2)
800 1000 1200 1400 1600 1800
Wavenumber (cm -1 )
1294
1358
1456
1700
1698
1705
(2)
(1)
15
Absorbance (a.u.)
0.30
0.25
0.20
0.15
0.10
0.05
1093
2807
979 1017
2856
2882
2856
0.00
2800 2900 3000
872
2902
2938
2949
792
2931
2948
706
(1)
Wavenumber (cm -1 )
a b
Figure 8. FT-IR (ATR) and FT-Raman spectra of compound 2; b) The high
wavenumber spectral region. Excitation: 1064 nm, 380 mW
Th e sp ect r a h igh ligh t t h e C 2 sy m m etr y o f t h e
co m p o u n d s a s well a s t h e p r e sen ce o f t h e co m m o n p ea k s
co r r esp o n d in g t o t h e r igid b icy clic sk e le t o n in t h e r a n ge
7 0 0 -1 8 0 0 cm -1 a n d 2 7 5 0 -3 1 0 0 . Th e Ra m a n sp ect r a su p p o r t
evid en t ly t h e en o l fo r m fo r co m p o u n d 1 (sy m m etr ic
vib r a t io n ν C=C a t 1 6 2 7 cm -1 ) a n d k e t o n e fo r m (sy m m etr ic
vib r a t io n ν C=O a t 1 7 0 0 cm -1)
1.4.3. Single crystal X-ray diffraction investigations
The molecular structure in solid state for compound 1 was obtained by
single crystal X ray diffractometry. These investigations revealed exclusively
the presence of enol tautomer which displays intramolecular H-bonds forming
between OH and carbonyl belonging to the ester group.
The internal torsion angles of the carbobcyclic rings are listed in Table 3.
Both six-membered rings (cyclohexene) adopt a flattened half-chair (C2)
conformation as indicated by the torsion angle C1-C2-C3-C4. The length
values of C3-C4 and C7-C8 bonds are situated around 1.33 Å indicating two
carbon-carbon double bonds. These presences reinforce the bicycle and induce
locally a planarity which brings forward the intramolecular H-bond O2-H O9
and O1-H O5.
The molecule adopts a chair-chair conformation with the ester groups
substituents situated symmetrically relative to the bridge.
2806
2902
2962
(2)

Figure 9. ORTEP diagram for the bicyclic tetraester 1
In fact, the six-membered rings of the bicyclic skeleton are cyclohexene rings,
which adopt a flattened half-chair conformation.
Figure 10. X-ray structure for the bicyclic tetraester 1 displayed by Mercury program
The distances from the hydrogen atoms of OH groups to the carbonyl
O atoms are shown as a dashed line and are d = 1.851-1.860 Å. These low
values suggest strong interactions by hydrogen bonds and a high stability of the
cyclic structures.
The investigations of the molecular structure of compound 2 by single
crystal X-ray diffractometry indicated exclusively the presence of ketone form,
which contains two carbonyl groups located at the positions 3 and 3a of the
molecule (Figure 11).
16

The molecule adopts a chair-chair conformation with the carbonyl groups
arranged symmetrically in endo relative to the bridge.
Figure 11. ORTEP diagram for the bicyclic dione 2
The six-membered rings of the bicyclic skeleton adopt a slightly flattened
chair-chair conformation due to the sp 2 hybridization of the carbon atoms C3
and C3a, and the molecule displays a C2 symmetry. This fact is evidenced by
the torsion angle C5-C1-C2-C3 as well as the bond angles situated around the
C3: O1-C3-C2 and O1-C3-C4a, specific for a carbonyl group atom (around
120º). The C3-C2-C4a bond angle is diminished due to the imposed constrains
by the geometry of the six-membered ring containing a sp 2 carbon atom.
Th e len gt h va lu es o f C3 -O1 a n d C3 a -O1 a b o n d s a r e sit u a t ed
a r o u n d 1 .2 2 Å in d ica t in g t wo ca r b o n -o xy gen d o u b le b o n d s,
wh ich su p p o r t t h e e xclu siv e p r esen ce o f k eto n e fo r m .
1.5. Molecular modeling
The goal of the theoretical study was the elucidation of the structure that
reproduces in the best manner the experimental IR and Raman spectra of the
compounds 1 and 2. The enolisable β-keto esters exhibit the phenomenon of
chelate ring formation through the intramolecular hydrogen bonds, similar
effects being observed in the case of the corresponding diketones [22].
17

1.5.1. Tetramethyl 3,7-dihydroxybicyclo[3.3.1]nona-2,6-diene-
2,4,6,8-tetracarboxylate structure
Two hypothetical structures for the investigated β-ketoester [23] were
theoretically calculated by DFT. One of them has the intramolecular hydrogen
bonds established between the enol hydrogen atom and the carbonyl oxygen
atom of the methoxycarbonyl group (Figure 5b). The second structure has the
intramolecular hydrogen bonds established between the enol hydrogen atom
and the methoxy oxygen atom of the methoxycarbonyl group (Figure 5a).
a b
Figure 5. Two possible conformations of the enol form: a) conf_A; b) conf_B.
The strength of the hydrogen bond shows a steady increase of the stability of βketoester
chelate, which closes a stable six-membered ring through such of
intramolecular weak interactions.
Figure 12. The optimized energetic state transition diagram for both conformations of 1
These two conformations were found to have an energetic barrier of only
0.2204 eV, which suggests a very fast interconversion between each other.
18

It can be concluded that the geometry of the conf_B structure is in better
agreement with the experimental data than that of the conf_A structure, on the
contrary with the single crystal X-ray diffraction.
1.5.2. Bicyclo[3.3.1]nonane-3,7-dione
The geometry structure of compound bicyclo[3.3.1]nonane-3,7-dione
was optimized using 6-31G Pople’s basis set by B3LYP with analytical
gradient method. The molecular structure of compound 2 shows two typical
C=O bonds and a bicyclic structure which exhibits a chair-chair conformation.
The molecular backbone conformation is identical with that of the compound 1.
The selected geometrical parameters (bond lengths and bond angles)
obtained at 6-31G** basis set are presented in the Table 7 (the index of atoms
is shown in Figure 21).
Figure 13. The optimized geometry of the diketone compound 2 obtained by
DFT method using B3LYP exchange-correlation functional
and 6-311++G** basis set.
19

Table 7. The selected molecular parameters of bicyclo[3.3.1]nonane-3,7-dione
calculated by DFT method using B3LYP exchange-correlation function with 6-
31G** basis set.
O1-C3
C3-C4
C4-H4
C4-H5
C4-C5
C5-C9
C5-C6
C3-C2
C9-C1
C9-H12
C4-C3-C2
Coord. B3LYP/6-31G**
Bond lengths (Å)
Angle (Degree)
20
1.2182
1.5252
1.1007
1.0941
1.5467
1.5396
1.5467
1.5252
1.5396
1.0977
116.466
1.6. Attempts of synthesis of bicyclic compounds of spiro-bis(1',5'-dioxane)
type
The synthesis of spiro-1,3-dioxane bicyclic compounds through acetalization
process starting from bicyclo[3.3.1]nonane-3,7-dione dione 2 and different
symmetrically 2,2-substituted 1,3-propanediols was an important step to create
a synthon bearing two functionalized sites, critically required in
macrocyclization reactions.
O O + 2
HO
HO
R 1
R 2
7 R 1, R 2: CH 3
8 R 1, R 2: CH 2Br
1. PTSA, C 6H 6, reflux
2. K10, MW
R 1
R 2
R 1, R 2: CH 3
R 1, R 2: CH 2Br
R 1
R 2

All the attempts to obtaine the desired bicyclo spiro- bis(1',5'-dioxane) failed
due to the strained geometry of the starting diketone 2, the mass spectrometry
analysis indicating only the presence of spiro-mono(1',5'-dioxane) compounds.
As depicted in Scheme 5, the acetalization reaction was carried out using two
different routes: the classic one (method a), consisting of the azeotropic
distillation, at reflux in benzene, catalyzed by PTSA [24] and under microwave
irradiation (method b), deposited on a solid support of Montmorillonite clay
K10 [25], followed by extraction with solvent in microwave oven.
O O +
OH
OH
R1 a. pTSA, C6H6, reflux
O
b. K10, microwave irrad.
R2 O
O
R1 R2 2 7 R1, R2: CH3 8 R1, R2: CH2Br 3 R1, R2: CH3 4 R1, R2: CH2Br Scheme 5. Acetalization reaction of compound 2 with 2.2-disubstituted-propane-1,3-diols
Table 8. Yields and reaction time for compounds 3 and 4 using method (a) and method (b)
Compound Yield (%) Reaction time Yield (%)
Reaction
Meth. (a)
(day) Meth. (b) time (min)
3 25 8 60 3
4 30 6 65 3
The advantages of the synthesis using method (b) over the method (a) lie in a
remarkably reduced reaction time, less toxic and inexpensive conditions of
reaction, as well as in the significantly increased yields. Also, it is worth
mentioning the absence of harmful solvents such as benzene or toluene, the
PTSA catalyst, and the facile work-up procedure.
1.6.2. NMR spectra in solution
The 1 H NMR spectra (Figure 14 a, b) of spiro compounds 3 and 4 revealed a
semi-flexible structure consisting of an anancomeric carbobicycle and a flexible
1',5'-dioxanic ring.
They display unique signals, with mean values of the chemical shifts, for the
axial and equatorial protons of the heterocycle (positions 2' and 4').
Thus, the spectrum of compound 3 (Figure 14a) exhibits two singlets
(δ=3.31 and δ=3.46 ppm) for axial and equatorial protons at 2'-C and 4'-C as a
consequence of the identical magnetic environment of the two protons and of
the heterocycle flipping. The 6 H singlet at δ=0.91 ppm is ascribed to the
protons of the equivalent methyl groups located at the position 3' of the
dioxanic ring, which exhibit a unique signal due to the flexibility of the ring.
21

a b
Figure 14. 1 H NMR spectrum (CDCl3, fragment) of: a)compound 3 (300
MHz); b)compound 4 (500 MHz).
The overlapped signals corresponding to the protons of the carbobicycle are
located in the range 1.5-2.5 ppm of the spectrum, their assignment being
partially elucidated yet.
The 1 H NMR spectrum of compound 4 (Figure 14b) displays unique signals
(two singlets) for the axial and equatorial protons of the flexible dioxanic ring
(δ==3.66 ppm at position 2' and δ==3.78 ppm at position 4').
Despite of the flexibility of the heterocycle, the bromomethyl substituents
located at position 3' exhibits two doublets characteristic for an AB system
instead of a singlet as in the case of the methyl substituents in compound 3.
This fact is due to the diastereotopicity of the Ha and Hb protons belonging to
the CHaHbBr groups, which give different signals, so they are not rendered
equivalent by conformational equilibrium. The correct assignment was possible
only in the 2D Heteronuclear spectrum, where the 13 C NMR spectrum signal at
δ=35.66ppm (3'-CH2Br secondary prochiral carbon atom) is correlated with the
both doublets ascribed to the methylenic diastereotopic protons (δa=3.56 ppm
and δb=3.47 ppm) of the bromomethyl groups.
The 13 C NMR spectrum of compound 4 (Figure 15) shows ten well
separated signals, attributed by the means of the 13 C NMR ATP and 2D
heteronuclear NMR (HMBC and HSQC) spectra.
22

At down-field appear two quaternary carbon atoms: the acetalic one (δ==98.05
ppm, 7-C) and that of the carbonyl group (δ==207.10 ppm, 3-C).
Figure 15. 13 C NMR spectrum APT (CDCl 3, 500 MHz, fragment) of compound 4
The secondary dioxanic carbon atoms at the position 2' and 4' are diastereotopic
and display different but very close signals (δ==63.42 ppm and δ==63.85 ppm).
The signal at δ=37.86 ppm is ascribed to the quaternary carbon situated in
position 3', whereas the bromomethyl substituents located at the 3'-C display a
unique signal at δ==35.66 ppm.
The spectrum also revealed the diastereotopicity of the secondary carbon atoms
2-C/4-C and 6-C/8-C, which exhibit two different signals (δ==37.11 ppm and
δ==45.54ppm). The bridgehead carbon atoms (1-C/5-C, tertiary) are located at
δ=28.59 ppm and the bridge carbon (9-C, secondary) at δ==63.85 ppm.
23

Figure 16. 13 C NMR spectrum APT (CDCl3, 75 MHz, fragment) of 3
The 13 C NMR spectrum of compound 3 (Figure23) displays different signals
for the secondary carbon atoms of the positions 2' and 4' (δ=68.22 ppm and
δ=70.09 ppm) of the dioxane ring, their diastereotopicity being correlated with
the presence of the rigid bicyclic fragment in the ketalic part of the heterocycle.
Also the primary carbon atoms belonging to the methyl groups at 3'-C exhibits
a unique signal very shielded at δ=22.64 ppm due to the flipping of the
heterocycle.
The peaks located at δ=32.59 and 96.84 ppm are assigned to the quaternary
carbon atoms at the position 3' and 7 of the flexible ring, the last one being
more deshielded due to the vicinity of the oxygen atoms from position 1' and 5'.
The signals corresponding to the carbon atoms of the carbocycle are situated in
the range 25-50 ppm of the spectrum as follows: δ==28.69 for 1-C/5-C,
δ==30.20 for 9-C, δ==37.27 for 6-C/8-C and δ==45.53 for 2-C/4-C. The small
signal at δ==207.11 ppm corresponds to the ketone carbonyl carbon at position
3 of the carboxycle and prove that the acetalization of diketone 2 underwent
exclusively with obtaining of the monospirane instead dispirane compound.
1.6.3. Mass spectra of monospirane
The 70 eV mass spectra of 5',5'-dimethyl-spiro{bicyclo[3.3.1]nonane-3,2'-
[1',3'-dioxane]}-7-one 3 and 5',5'-bis(bromomethyl)spiro{bicyclo[3.3.1]nonane-
3,2'-[1',3'-dioxane]}-7-one 4 (Figure 17) reveal high abundance peaks for the
molecular ions [M] +· , 238 and 394, respectively. This fact indicate indicating
very stable molecules, unlike the data found for other highly ramified
molecules with dioxane sequence [16-18]. Also, there are proofs that support
the fact that only spiro-monodioxane compounds have been obtained through
acetalization reaction of compound 2.
24

a
b
Figure 17. 70 eV EI mass spectra of: a) compound 3, b) compound 4
1.6.4. FT-IR measurements
Beside the NMR spectroscopy, especially the 13 C NMR one, FT-IR
spectroscopy is one of the most powerful tool that can establish the nature of
the spiro-compounds obtained in the acetalization reactions of compound 2:
mono- or dispiro 1,3-dioxane derivatives.
FT-IR spectra in solid state, recorded in KBr matrix for both compounds 3 and
4 (Figure 18), revealed the presence of carbonyl stretching frequency at about
1724 and 1684, respectively [27].
25

Absorbance (a. u.)
Absorbance (a.u.)
0.12
0.09
0.06
0.03
0.00
0.20
0.15
0.10
0.05
0.00
396
360
517
578
679
774
803
923
986
1020
1047
1113
1133
400 600 800 1000 1200 1400 1600 1800
476
649
679
750
Wavenumber (cm -1 )
850
989
1020
a
26
1262
1367
cetodimethyl 3
1451
1471
400 600 800 1000 1200 1400 1600 1800
Wavenumber (cm -1 )
b
1100
1135
1248
1264
ceto dibromomethyl 4
1341
1373
1426
Figure 18. FT-IR spectra recorded in KBr matrix of: a) compound 3; b) compound 4.
All the attempts to obtain this type of double functionalizate sites substrate
through the acetalization reactions failed, due to the geometry adopted by the
bicyclic diketone.
In the given conditions we concluded that two 1,3-dioxane units cannot be
introduced in the molecule of dione 2 and smaller functional groups such as
oxime are more appropriate to obtain the desire substrate.
2. Bicyclo[3.3.1]nonane-3,7-dione dioxime
The oximes are organic compounds that contain functional moiety -
C(R)=N-OH. The carbon-nitrogen double bond constitutes true physical
analogues to the carbon-carbon double bond and its presence in the molecule
brings the formation of two geometric stereoisomers: cis and trans.
1474
1680
1724
1684
1730

Stereoisomerism of the oximes is a consequence of the spatial arrangement,
relative to the rigid C=N bond, of the OH group belonging to the oxime moiety
and of a substituent located at the carbon atom. Isomers cis and trans terms are
replaced by isomers syn and anti in the molecules containing two oxime
groups. They are denoted syn and anti relative to the orientation of the OH
groups belonging to the oxime moieties to the same side or across of the axis
that go through the C=N bonds.
Dioximes represent an interesting class of organic compounds which
exhibit both acidic and basic character within the same function [28]. In this
respect, the oxime moiety might be pass for a supramolecular connector that
can generate supramolecular structures through complementary hydrogen
bonds involving dimeric or trimeric motif [30] or due to the lone electron pair
of the nitrogen atom, which gave it a significant transition metals complexing
capacity [29].
2.2. Synthesis of syn and anti isomers
The synthesis of bicyclo[3.3.1]nonane-3,7- dioxime 5 starting from dione 2 was
an important route to create a synthon bearing two functionalized sites,
critically required in macrocyclization reaction.
The dioxime 5 of bicyclo[3.3.1]nonane-3,7-dione 2 has been already
synthesized [7abc] but the reactions underwent with the obtaining of the
mixture of syn and anti isomers of dioxime 5.
In our case the synthesis of 5 was performed using an improved procedure of a
method already described in the literature [33] (Scheme 7).
CH3-COONa, H2O O O + 2H2N
OH
OH N
MeOH, rt
2 5-syn
5-anti
27
N OH
Scheme 7. Synthesis of bicyclo[3.3.1]nonane-3,7-dione dioxime 5 starting from dione 2
and hydroxylamine hydrochloride
Bicyclo[3.3.1]nonane-3,7-dione 2 was treated with a large excess of
hydroxylamine hydrochloride in the presence of sodium acetate at room
temperature to give its dioxime 5 in good yields. It is worth mentioning that
several attempts of synthesis following the literature data [33] failed, the yields
being very low. In this light, the protocol was changed by adding the solution
of hydroxylamine hydrochloride and sodium acetate in water to the

icyclo[3.3.1]nonane-3,7-dione solution in water/ethanol instead of being the
other way around [33]due to the poor solubility of dione 2 in ethanol.
As novelty, syn and anti isomers of 5 have been isolated for the first time by
column chromatography. The static and dynamic stereochemistry of the
isolated isomers and the possibilities to build up supramolecular architectures
for each isomer by stereospecific H bonds interactions have been investigated.
Stereochemistry of the dioximes
Th e st er eo ch em ist r y o f t h ese d io xim e s is d iscu ssed
a cco r d in g t o t h e p ecu lia r a xia l ch ir a lit y o f
a lk y ly d en e cy clo a lca n es [3 4 ] wh ich is sim ila r t o t h a t o f
cy clo h exa n o n e o xim e ( 5 , Sch e m e 8 ).
N N
HO HO
HO
N
HO
N
8
28
a
OH
N
N N
HO OH
OH
N
aS
aR
N N
HO OH
aSaR aSaS aRaR
(5-syn; unlike)
5-anti; like)
b
Sch e m e 8
Dioxime of bicyclo[3.3.1]nonane-3,7-dione (2) exhibits two chiral axis (the
C=N bonds) and the syn isomer is an unlike form (aRaS), while the anti isomer
is chiral (like isomer: aSaS and aRaR). Due to the rigid structure of the
bicyclo[3.3.1]nonane skeleton these three stereoisomers are separable.
The formation in the case of the anti isomer of homochiral dimers by
enantiospecific recognition could have many applications in chiral

discrimination by self assembly processes if one starts from the separated
enantiomers of dioxime 5.
2 .3 . In vestigatio n s in so lu tio n
Th e 1 H NMR sp ect r u m o f sy n iso m er (Figu r e 1 9 ) p r e sen t s
sign ifica n t ly d esh ie ld e d b r o a d sign a l (2 H, δ ==1 0 .1 0 p p m )
co r r esp o n d in g to th e p r o t o n s o f t h e o xim e m o iet ie s in vo lv ed
in t h e H-b o n d s fo r m in g.
At δ =2 .9 8 p p m is a 2 H sign a l (d , J=1 5 .3 Hz) a ssign ed t o
t h e eq u iv a len t eq u a t o r ia l p r o t o n s lo ca t ed a t 4 -C/ 6 -C, wh ich
a r e co u p led wit h t h e co r r e sp o n d in g a xia l p r o t o n s (AB
sy st em ). Th e p ea k s a p p ea r b r o a d er d u e t o a wea k co u p lin g
wit h t h e b r id geh e a d p r o t o n s 1 -H a n d 5 -H.
Th e sp ect r u m d isp la y s in t h e r a n ge 2 .3 2 -2 .1 0 p p m a few
o ver la p p ed p ea k s, in t e gr a t ed fo r 6 H, wh ich ca n b e a t t r ib u t ed
t o t h e eq u a t o r ia l a n d a xia l p r o t o n s lo ca t ed a t 2 -C/ 8 -C a n d t o
t h e a xia l p r o t o n s a t 4 -C/ 6 -C.
Figure 19. 1 H NMR spectrum of compound syn-5a (300 MHz, DMSO-d 6).
In t h e r a n ge 1 .8 5 -1 .7 6 p p m t h e d o u b let o f d o u b let s (p se u d o )
a t δ ==1 .8 2 p p m is o ver la p p ed wit h t h e m o r e sh ield ed
29

m u lt ip let a t a t δ ==1 .7 6 p p m . Th e m o r e co m p lex p a t t er n o f
t h e sp ect r u m is d u e t o t h e n o n -eq u iv a len ce o f t h e
b r id geh ea d p r o t o n s 1 -H a n d 5 -H.
Figure 20 1 H NMR spectrum of compound anti-5b (300 MHz, DMSO-d 6)
The 1 H NMR spectrum of anti isomer (Figure 21) displays a 2H small
broad signal at far down-field (δ==10.12 ppm), assigned to the protons
belonging to the oxime moieties. The strong deshielding of these protons
indicates their participation in the H-bonds.
At δ=2.99 ppm it presents a 2H doublet (J=15.3 Hz) ascribed to the equatorial
protons located at 2-C/6-C due to the geminal coupling with the axial protons
(AB system). It displays also a slight tendency of splitting due to the weak
coupling in a W path with the bridgehead protons 1-H and 5-H.
In the range 2.07-2.26 ppm the spectrum shows several overlapped peaks,
integrated for 6H, corresponding to the equatorial and axial protons at 4-C/8-C
as well as to the axial protons at 2-C/6-C.
The spectrum displays also a well separated signal (δ=1.85 ppm, dd) for the
equivalent bridgehead protons at the position 1 and 5. Its pattern suggests a
vicinal coupling with the equatorial protons at 2-C/6-C and 4-C/8-C, as well as
a weak coupling with the axial ones (specific interactions have been observed
in 2D COSY spectrum).
Th e 2 H sign a l a t δ =1 .7 6 p p m is a ssign ed t o t h e p r o t o n s
lo ca t ed a t p o sit io n 9 a n d a p p e a r s a s a m u lt ip let d u e t o t h e
30

wea k co u p lin gs in W wit h t h e a xia l a n d eq u a t o r ia l p r o t o n s a t
2 -C/ 6 -C a n d 4 -C/ 8 -C, r esp ect iv ely .
The difference between syn and anti isomers can be observe clearly in
13 C NMR sp ect r u m .
Figure 21 13 C NMR spectrum of compound anti-5b (300 MHz, DMSO-d 6)
The 13 C NMR spectrum (Figure 21) of the anti isomer is very similar to that of
the syn one (Figure 22) but it displays only five peaks, the tertiary bridgehead
carbon atoms 1-C and 5-C being represented by a unique signal (δ==29.12
ppm) instead of two signals as in the case of syn isomer.
31

Figure 22. 13 C NMR APT spectrum of compound syn-5a (300 MHz, DMSO-d 6)
The small signal situated at δ=32.60 ppm is ascribed to the secondary carbon of
the bridge (9-C), whereas the bridgehead carbon atoms 1-C and 5-C appear at
different chemical shifts (δ==27.68 ppm and δ==29.56 ppm). Their
diastereotopicity can be explained in the light of the positioning at opposite
sides relative to the C3-C9-C7 plan, one of them being influenced by the
oximic OH groups and the other one by the lone pair of the nitrogen atoms.
At high frequency appears a low intensity signal assigned to the quaternary
carbon atoms 3-C and 7-C belonging to the oxime groups (δ==154.12 ppm).
Both 1 H NMR spectra of the syn and anti isomers display a 2H doublet in the
region 3.03-2.96 ppm , well separated but exhibiting close chemical shifts so
that allow to establish the sin/anti ratio in a mixture of isomers simply dividing
the integrated value of the doublet for each isomer. This fact give us the
possibility to investigate the synanti isomerisation.
2.3.2. NMR study of kinetics of the synanti isomerisation
Under acidic conditions the syn and anti isomers of dioxime 5 are in a running
equilibrium (Scheme 9; similar equilibria were observed for other dioximes,
too) [35].
32

Scheme 9
This equilibrium was investigated using 1 H NMR spectra. The experiments
were based on the differences of the chemical shifts for the equatorial protons
at positions 2,4,6,8 belonging to the syn (4e,6e = 3.48 ppm) and to the anti
isomers (2e,6e = 3.36 ppm).
Figure 23. Part 1 H-NMR spectrum of a crude mixture of syn and anti isomers of
dioxime 5
The experiments were run starting from either the pure syn or anti
isomers and were based on the recording of the 1 H NMR spectra of the same
sample over several periods of time and on the measuring in these spectra of
the ratios between the isomers using the intensities of their specific signals
(Figures 24 and 25).
33

Figure 24. NMR investigation of the antisyn isomerization of 5
Figure 25. NMR investigation of the synanti isomerization of 5.
The collecting of data (Table 8) was made at shorter intervals at the beginning
of the process and for the calculation of ratios mean values of the integrals were
used.
34

Table 8 Data (time/ratio of isomers) of the kinetic measurements for the
synanti equilibrium in 5.
Synanti Antisyn
Nr. 5a syn 5a anti
Time (min) Ratio
Time (min) Ratio
syn/anti
anti/syn
1 0 1:0 0 1:0
2 7 1:0.096 17 1:0.038
3 16 1:0.159 34 1:0.157
4 28 1:0.254 51 1:0.200
5 50 1:0.427 68 1:0.250
6 68 1:0.560 85 1:0.320
7 84 1:0.675 102 1:0.418
8 101 1:0.796 119 1:0.447
9 118 1:0.891 136 1:0.467
10 135 1:0.958 153 1:0.481
11 152 1:1.033 170 1:0.532
12 169 1:1.088 187 1:0.540
13 183 1:1.150 204 1:0.550
14 200 1:1.162 221 1:0.578
15 217 1:1.218 272 1:0.640
16 At equilibrium 1:1.437 At equilibrium 1:0.696
The reaction was considered to be of first order and the pH (3.17) of the
solvent was fitted (with F3C-COOH) to obtain a convenient “time scale” for the
process.
xe
k1 k t .
xe
x
k1 K
k
ln 1
1
The experimental results (calculated with relations 1 and 2) are shown in Table
9.
Table 9. Kinetic parameters (k 1; k -1) for isomerization of 5 starting from syn and anti
isomers
Starting
isomer
Initial
concentration
35
K k1x10 -3
min -1
(1)
(2)
k-1x10 -3
min -1

(mol·l -1 )
syn 8.8 x10 -3 1.4373 5.10 3.549
anti 8.8 x10 -3 0.69574 3.774 5.425
In equations (1) and (2) k1 and k-1 are the forward and reverse reaction rate
constants, K is the equilibrium constant, xe is the initial concentration of the
starting isomer, x is the concentration of the same isomer at the “t” time.
2.3.3. Chiral HPLC studies
In order to establish the chiral behavior of syn and anti isomers of compound
5, already separated by flash chromatography, a mixture of these isomers was
subjected to HPLC separation using a chiral stationary phase.
Figure 26. Chromatogram obtained during the chiral HPLC resolution of the mixture of
stereoisomers of compound 5.
The three separated peaks (Figure 37) correspond to the anti: tR1 = 12.443 min,
tR2 = 13.762 min and syn: tR3 = 15.011 min isomers.
The ratio syn/anti was found to be 71.80:28.19 (Table 10), which is in good
agreement with the value determined by 1 H-NMR investigations (73:27).
2.3.4. FT-IR study
The FT-IR investigations(Figure 27) of 5-syn and 5-anti in aprotic solvent (10.0
mM; CHCl3) in a large range of concentrations (from 10.0 mM to 0.156 mM)
revealed only absorption bands corresponding to the H bonds associated
molecules (υsyn = 3110/3202 cm -1 ; υanti = 3164/3295 cm -1 ). In order to break the
supramolecular structures tetrachloroethylene (C2Cl4) was used as aprotic and
non-polar solvent to evidence the presence of the monomer in FT-IR spectrum.
36

a
Figure 27. FTIR spectra in solution recorded at different concentrations of dioxime
isomers in a 1:1 mixture of CHCl 3 and C 2Cl 4: a) syn; b) anti.
At higher concentrations (5-syn or 5-anti) the spectra exhibit only the bands
corresponding to the associated molecules. The bands corresponding to the
dioxime monomers (υsyn = 3696 cm -1 ; υanti = 3684 cm -1 ) could be observed by
decreasing the concentrations of the investigated solutions. The intensities of
these bands, corresponding to the free dioximes, increase with the dilution and
at 0.156 mM the monomer/associated molecules ratio could be appreciated to
be 0.3 for the syn and 0.15 for the anti isomer, respectively.
Figure 28 and 29 present the 3D infrared spectra recorded for seven
solutions with different concentrations of anti and syn isomer varying from
0.156 mM to 10 mM.
a b
Figure 28. 3D FTIR spectra in solution recorded at different concentrations of anti
isomer in a 1:1 mixture of CHCl 3 and C 2Cl 4: a) 3075-3700 cm -1 ; b) 3670-3700 cm -1
An inside detail in the 3670-3700 cm -1 spectral range reveals an increase of
the monomer absorbance when the dioxime concentration decreases from 2.5 to
0.156 mM.
37
b

a b
Figure 29. 3D FTIR spectra in solution recorded at different concentrations of syn
isomer in a 1:1 mixture of CHCl 3 and C 2Cl 4: a) 2800-3750 cm -1 ; b) 3660-3740 cm -
1 .
2.4. Investigation of bicyclo[3.3.1]nonane-3,7-dione dioxime in solid state
The solid state FTIR investigations revealed for both 5-syn and 5-anti structures
the recording of only the O-H absorption bands corresponding to the H bonds
associated molecules. The infrared spectra for the dioxime isomers in solid
state do not show an absorption around 3600 cm -1 , characteristic of free OH
[38].
a b
Figure 30. FT-IR spectrum of: a) 5-anti dioxime b)5-syn dioxime, dispersed
in KBr matrix
They tend to establish H-bond in solid state and the O-H stretching frequencies
are shifted to 3328-3281 cm -1 and 3190-3109 cm -1 for anti and syn
configuration, respectively (Figure 30).
2.4.2. Single crystal X-ray diffraction
38

These investigations revealed the obtaining of associations of molecules which
form spectacular supramolecular aggregates. The anti isomer gives a cyclic
dimer by four hydrogen bonds (Figure 31).
a
b
Figure 31. ORTEP diagram for the cyclic dimer of 5-anti (a : aRaR – aRaR ; b : aSaS
– aSaS associations)
The association of the molecules is homochiral and involves either aRaR (a)
or aSaS (b) structures (the dimers are built up by highly selective enantiomeric
recognition processes). The crystal is more or less a homogenous solution of
the two enantiomeric dimers (it is a racemate).
Syn isomer forms a supramolecular wheel via a cyclic trimer built up by six
hydrogen bonds (Figure 32). Both analyzed structures exhibit a chain-chain
conformation, according to the torsion angles values.
39

Figure 32. ORTEP diagram for the cyclic trimer of achiral 5-syn isomer.
The distances from the hydrogen atoms of OH groups to the N atoms
are d = 1.842-1.974 Å in the dimer and d’ = 1.676 – 1.848 Å in the trimer,
respectively. These low values suggest strong interactions by hydrogen bonds
and a high stability of the cyclic structures.
The investigations of the lattice for 2-syn revealed a layered structure
with transversal (along the crystallographic axis a) and longitudinal (along the
crystallographic axis b) channels (Figure 33).
Figure 33. View of the lattice (along the c crystallographic axis) of 5-syn.
40

2.6. Molecular modeling for the supramolecular architectures of syn and
anti isomers
The geometry optimization of syn and anti isomers of bicyclo[3.3.1]nonane-
3,7-dione dioxime were performed using the Gaussian 03 program package
[44] considering the B3LYP density functional theory method with 6-31G**
basis set (including polarization functions for all atoms).
The molecular modeling at ab initio level was used to investigate the structures
of syn and anti isomers of compound 5. These investigations revealed only the
formation of the cyclic trimer for syn structure.
5-syn (trimer)
The stabilization of the trimer by H-bonds was evaluated at Δ=G° = 59.08 kcal
/ mol (Δ=E°/dioxime molecule = 19.69 kcal / mol). The calculated distances
from the H atoms of the OH groups to the N atoms of the other molecules are in
the range d = 1.835-1.839 Å.
Intermolecular interaction energy: Δ=EABC = 59.08 kcal/mol (Δ=EABC/Nmolec =
19.69 kcal/mol)
C1 – C2 distance = 9.824 Å
C2 – C3 distance = 9.837 ÅC C 9.
829 Å
C3 – C1 distance = 9.826 Å
H1 … N2 = 1.836 Å H4 … N5 = 1.837 Å
41

H2 … N3 = 1.839 Å H5 … N6 = 1.838 Å
H3 … N1 = 1.838 Å H6 … N4 = 1.835 Å
N1 … N2 = 3.496 Å N4 … N5 = 3.495 Å
N2 … N3 = 3.496 Å N5 … N6 = 3.492 Å
N3 … N1 = 3.488 Å N6 … N4 = 3.491 Å
O1 … O2 = 3.794 Å O4 … O5 = 3.794 Å
O2 … O3 = 3.793 Å O5 … O6 = 3.790 Å
O3 … O1 = 3.795 Å O6 … O4 = 3.793 Å
N1 … N4 = 3.735 Å
N2 … N5 = 3.730 Å
N3 … N6 = 3.734 Å
V molec = 1766.78 Å 3
For the anti isomer the energy modifications brought by the formation of
the cyclic dimer (Δ=G° = 30.43 kcal / mol; Δ=E°/dioxime molecule = 15.21
kcal / mol) and of the cyclic trimer were also calculated (Δ=G° = 54.57 kcal /
mol; Δ=E°/dioxime molecule = 18.19 kcal / mol). The calculated distances
from the H atoms of the OH groups to the N atoms of the partner molecules are
d = 1.928 Å for the dimer, and they cover the range d = 1.803-1.897 Å for the
trimer. Despite the higher calculated stability for the trimer of anti isomer, it
crystallizes in the dimer form, maybe due to the contribution of other packing
forces.
5-anti (dimer)
Intermolecular interaction energy: Δ=E AB = 30.43 kcal/mol (Δ=E AB/N molec = 15.22
kcal/mol)
42

C 1 – C 2 distance = 10.505 Å
H 1 … N 2 = 1.928 Å
H 2 … N 1 = 1.928 Å
H 3 … N 4 = 1.928 Å
H 4 … N 3 = 1.928 Å
N 1 … N 2 = 3.038 Å N 1 … N 3 = 3.439 Å
N 3 … N 4 = 3.038 Å N 2 … N 4 = 3.440 Å
O 1 … O 2 = 3.248 Å
O 3 … O 4 = 3.248 Å
43

2. Conclusions of the part A
Different saturated bicyclic compounds derived from tetramethyl 3,7dihydroxybicyclo[3.3.1]nona-2,6-diene-2,4,6,8-tetracarboxylate
1 have been
synthesized: diketone 2, spiro-monodioxane 3 and 4 and dioximes 5a and 5b.
The structural analysis has been performed by X-ray diffraction (four
single crystal structures), NMR at 300 MHz and 500 MHz, mass spectrometry,
FT-IR in solid state and in solution, and molecular modeling.
Synthesis of diketone 2 from precursor 1 was carried out following a novel
and uncatalysed straightforward strategy, classic and under microwave
irradiation, involving a one-step hydrolysis-decarboxylation route.
The structural analysis in solution and in solid state highlighted exclusively
the ketone form for compound 2 and the enol form, stabilized by intramolecular
H bonds, for the tetraester precursor 1.
Two possible structures of the enol form of compound 1, stabilized by
intramolecular H-bond between the enol ρ(C-O-H) fragment and ester groups
(carbonyl or methoxy fragment) have been modeled. The difference of energy
between these two forms, estimated from the theoretical work, is very low,
suggesting a fast inter-conversion between each other, .and the preference of
the H-bond interactions for the carbonyl fragment (confirmed by single crystal
X-ray diffraction).
The spiro-monodioxane 3 and 4 display a semi-flexible structure due to the
bicyclic skeleton rigidity and exhibit axial and elicoidal chirality, demonstrated
by the diastereotopicity of the 2'-C and 4'-C carbon atoms of the dioxane ring as
well as by the diastereotopicity of the Ha and Hb protons belonging to the
prochiral carbon atom of the bromomethyl substituent (compound 4).
The bicyclic dioxime 5 exhibits a particular case of axial chirality and the
corresponding stereoisomers syn and anti have been separated. The
thermodynamic and kinetic parameters of the syn-anti equilibrium were
determined by 1 H- NMR experiments.
Isomer syn (5a) is achiral (unlike) and isomer anti (5b) is chiral (like). The
chiral compound 5b was analyzed by chiral HPLC and its enantiomers were
discriminated.
The separated syn and anti isomers form stable H-bonds driven
supramolecular structures (cyclic dimer and trimer) by enantio- and
diastereospecific processes of self assembly based on four and six hydrogen
bonds, respectively. The structures are supported by single crystal X-ray
diffraction, FT-IR in solid state and in solution, NMR and molecular modeling.
44

Selected references
1. (a) K. Frische, M. Greenwald, E. Ashkenasi, N.G. Lemcoff, S. Abramson, I.
Golender, B. Fuchs, Tetrahedron Lett. 1995, 36, 9193-9196; (b) A. Merz, L.
Gromann, A. Karl, T. Burgemeister, K. Kastner, Liebigs Ann. 1996, 10, 1635-
1640, (c) D. Ranganathan, V. Haridas, I. L. Karle, , Tetrahedron 1999, 55,
6643- 6656 ; (d) B. J. Bridson, R. England, M. F. Mahon, K. Reza, M.
Sainsbury, , J. Chem. Soc. Perkin Trans. 2 1995, 10, 1909-1039.
1
2. P. Yates, E. S. Hand, G. B. French, , J. Am. Chem. Soc. 1960, 82, 6347-
6353.
3. H. Stetter, H. Held, A. Schulte-Oestrich, , Chem. Ber. 1962, 95,1687-1691.
4. L. M. Jackman, S. Sternhell, “ Applications of Nuclear Magnetic Resonance
Spectroscopy in Organic Chemistry”, 2 nd ed., Pergamon Press: Oxford, 1969,
334-335.
5. S. H Bertz, G. Dabbagh, Angew. Chem, Int. Ed. Engl. 1983, 21, 303; (b) R. D
Sands, J. Org. Chem. 1983, 48, 3362-3363.
6.(a) M. M. Folkendt, B. E. Weiss-Lopez, J. P. Chauvel Jr, N. S. True, , J.
Phys. Chem. 1985, 89, 3347-3352; (b) T. Ishida, F. Hirata and S. Kato, J.
Chem. Phys. 1999, 110, 3938-3945; (c) Y. Park and C. H. Turner, , J.
Supercrit. Fluids 2006, 37, 201-208.
7. N. Tosa, A. Bende, S. Cîntă Pînzaru, I. Grosu, and E. Surducan, Studia Univ.
Babes-Bolyai, Physica , 2004, 44, 289-292.
8. E. Mesaros, I. Grosu, S. Mager, G. Plé, I. Farcas, , Monatsh. Chem. 1998,
129, 723-733.
9. F. Matloubi Moghaddam, A. Sharifi, , Synth. Commun. 1995, 25, 2457-2461
11. I. Fenesan, R. Popescu, C. T. Supuran, S. Nicoara, M. Culea, N. Palibroda,
Z. Moldovan, O. Cozar, Rapid Commun Mass Spectrom., 2001, 15, 721-729.
11. S. Mager, N. Palibroda, I. Grosu, M. Horn, Studia Univ. Babes-Bolyai,
Chemia, 1983, XXVIII, 14-19.
12. M. Culea, N. Palibroda, S. Nicoara, O. Cozar, I. Oprean, I. Fenesan, Studia
Univ Babes-Bolyai, Physica, 1991, XXXVIII, 11-21.
13. A. Mitra and M. Dutta Gupta, Tetrahedron 1976, 32, 2731-2733.
14. B. D. Gupta, R. Yamuna, and D. Mandal, Organometallics 2006, 25, 706-
714.
15. I. Grosu, E. Bogdan, G. Plé, L. Toupet, Y. Ramondenc, E. Condamine, V.
Peulon-Agasse, M. Balog, Eur. J. Org. Chem. 2003, 16, 3153-3161.
16. N. Toşa, A. Bende, R. A. Varga, A. Terec, I. Bratu and I. Grosu, J. Org.
Chem. 2009, 74, 3944-3947.
17. A. Strenger, P. Rademacher, Eur. J. Org. Chem. 1999, 7, 1611-1617.
18. I. Grosu, M. Balog, S. Mager, Rev. Roum. Chim. 2005, 50, 333-339.
19. (a) J. W. Fraser, G. R. Hedwig, M. M. Morgan, H. K. Powell,. J. Aust. J.
Chem. 1970, 23, 1847-1852; (b) H. K. J Powell, J. M. Russell Aust. J. Chem.
1977, 30, 1467-1473.
45

20. L. J. Bellamy, “Advanced in Infrared Group Frequencies”, Methuen: New
York, 1968.
46

Part B
Fabricatio n o f 3 D Metallic Micro - an d n an o stru ctu re s
by Lase r In d u ced Pho to ch e m istry
1. Principle of nanostructuration by two-photon induced photochemistry
In the last decade, two-photon absorption (TPA) processes have been
intensively studied and improved for 1D, 2D and 3D micro/nanostructures
fabrication. The main aspect consists of a spatial confinement of the chemical
process in a small volume at the focal laser point. In spite of this advantage, the
first attempts have been done only in 1992 by Wu et all [1] who observed the
possibility of two-photon excitation by a femtosecond laser of some resins used
in microelectronics.
Five years later, in 1997, Maruro [2] have presented different threedimensional
structures obtained by this approach through a radical mechanism.
TPA technique has been applied succesfully for 3D polymer fabrication process
[3] but not for metals. For the first time Wu et all achieved to obtained threedimensional
metallic structures using a photographic-like approach within a
sol-gel dielectric matrix [4]. The 3D latent image was generated by a
femtosecond laser irradiation inside the photographic medium thanks to the use
of a high numerical aperture objective.
a a
Figure 1. Three-dimensional spiral structure produced within silver-doped solgel
materials by two-photon absorption (the latent image)
Continuous laser radiation does not induce the reduction, whereas
increasing the pulse width, in certain conditions of exposure, the rate of
reduction is reduced, suggesting the decisive role of multiphoton absorption
process.

2. Experimental part: fabrication and characterization
The process of micro/nanofabricationby TPA consists of three main parts from
the experimental point of view: the chemical part, the properly metallic
fabrication part, and the metallic structures characterisation part.
The chemical part involves sample preparation, glass substrate coating by a
polyimide adherent layer, and preparation of thin films (from aqueous
solutions) by spin-coating. The metallic fabrication process requires the
performance of a complex experimental set-up in order to deliver the laser
beam within the sample active layer. The characterisation of nanostructures
involves the use of optical and spectroscopic techniques, correlated with
scanning electron microscopy (SEM) and atomic force microscopy (AFM).
Figure 2 presents a section view of the laser beam way inside the microscope
which illustrate its interaction with the sample.
Laser beam
Figure 2. Inside view of the microscop-enlarging of the sample
3 Optimisation of silver nanostructures fabrication
Silver is a well-known soft white lustrous noble metal, characterised by the
highest electrical and thermal conductivity for a metal as well as by its
oxidizable character
Different techniques using light to fabricate silver were developed because its
already known and remarcable applications in photographic art as well as for
the new applications in nanophotonics and nanoelectronics. These new topics
are related with the surface plasmon properties of silver and particulary with
their surface-enhanced Raman effect which increases the Raman measurement
by order of magnitude [8,9].
3.2. TPA approach of silver photographic process
1

Our objective was to fabricate silver nanostructures using a two-photon
absorption photochemical process that occurs at the laser beam spot. Due to its
nonlinear character, the light absorption is highly localized in a small volume
near the focal point and allows the laser writing fabrication in three-dimensions
through a deep penetration within the material.
The general redox process of silver ions reduction at the laser focal point can be
written:
Silver salt (water soluble) + Fe(III)citrate complex Silver(water
insoluble) + Fe(II)citrate complex
Preliminary experiments performed by laser irradiation of an aqueous solution
of silver salt and sensitizer generated within solution a large amount of colloids
instead of a solid structure.
Figure 3. Optical image of silver colloids recorded in dark-field with x20 objective
The dark-field image from Figure18 displays the light scattering from dispersed
silver colloids using white-light illumination.
The key point of our experiment was to increase the solution viscosity which
allows to control the rate of reduction and to keep the metallic deposition
localized in the small volume at the focal point during the laser action and after
it stops.
In this respect we chose the poly (4-styrenesulfonic acid), denoted PSS that
embodies all these properties, as a system stabilizer. Thus, we created a
chemical system that contains silver nitrate as active specie and ammonium
ferric citrate as sensitiser, dispersed into a PSS matrix. It offers the possibility
to fabricate continuous and well defined silver nanostructures by two-photon
absorption.
3.3. TPA fabrication of silver wires
Networks of continuous silver lines were fabricated using the chemical system
containing the active species included in the PSS polymer host.
2

3 m
30 m
a b
Figure 4. Optical images of a silver wires network recorded with: (a) x20
objective, (b) x100 objective; inset of SEM image of a silver wire.
3.3.2. Thermal effect limitation
After removing the polymer matrix it was proved that in both cases a double
line, centered on the area of engraving, is obtained. This confirms the same
behaviour that has been reported recently for the fabrication of silver wires
[13].
The double line is characterized by the width, measured at the half-maximum,
and the distance between lines, measured between the ridges inside of the
double line (Figure 20).
Distance between lines
3
Width
Figure 5. SEM image of a silver double wire written at 50 mW

Figure 5 shows the SEM image of a silver double wire, recorded at 1.0 μm
scale and 20000x magnification, which indicates a line width of almost 500 nm
and a distance between lines of 1.2 μm.
Taking in account that the distance between lines is 1.2 μm and the diameter of
the laser spot at the focal point is evaluated to 700 nm, we may point out that
the local thermal effect plays a decisive role among the shape of the metallic
features in the deposition process. The lack of deposition at the line center
suggested that thermal effect induced further the metallic particles ablation
after deposition process.
From this point of view the chemical system containing ammonium ferric
citrate as sensitizer and reducing agent reveals a limitation induced by the local
thermal effect that will generate the double wire and will decrease the purity of
silver structures.
3.6. TPA fabrication of 2D and 3D silvermicro/nanostructures
Metallic silver 2D and 3D structures have been fabricated using the
chemical system that contains silver nitrate dispersed into a PSS matrix.
When the laser is moved in the x-y plane of the sample we can fabricate lines.
As a result when the laser is not moved during the fabrication we obtain a dot
instead of a line. The photo-reduction of silver ions was performed within a 48
hours old thin film, obtained by spin-coating. The surface of a 2.5x2.5 cm
microscope slide was modified with polyimide in order to improve the
attachement of silver structure onto the surface during the fabrication [7]. The
2D structures were written using a 100xPH3 immersed-oil objectiv with 1.25
NA.
A dots network with a period of 5 m was designed using increasingly
exposure times from 1s to 7s, and powers ranging from 1 mW to 8 mW, at
0.5m/s and DT of 2 ms (Figure 6).
a b
Figure 6. Optical images recorded with a x100Ph3 oil-immersed objective
4

(NA 1.25) in phase-contrast (a) and transmission (b).
In figure 7 we can see SEM views of dots deposited at 6mW and 6s exposure
time, recorder at 4000 order of magnitude and 5 m scale. We notice that the
results essentially depend on the total amount of laser energy sent. As already
discussed, we see that most of the produced dots are actually rings, only the
extremely small ones can be dots without hole.
Figure 7. (a) SEM image of a silver dots network fabricated at different laser
powers and exposure time ; (b) Silver dot obtained at 6mW and 6s exposure
time
3.6.2. 3D structures
Three dimensional silver structures were fabricated using the same chemical
system presented for dot and line fabrication.
The TPA reduction of silver ions was performed within a 12 hours old thick
film, obtained by deposition of a droplet of the solution on the substrate. The
surface of a 2.5x2.5 cm microscope slide was modified with polyimide in order
to improve the attachement of silver structure onto the surface during the
fabrication [29].
The 3D structure was written using a 100xPh3 immersed-oil objectiv lens
with 1.25 NA, to deliver 4-5 mW of power to the sample. The lines can be
generated by translating the stage in the XY-directions at a velocity of 0.5 m/s
and a DT of 2 ms.
Connection between XY translation and displacement of the sample holder in
the Z-direction with a computer programm allowed to obtain a woodpile-like
structure as a 10 degree tilted quadratic prism, with 20 m width of base along
x and y axis, and 14.4 m total height. The three-dimensional object consists of
12 layers, each layer containing 6 lines with 4 m period, oriented
alternatively, parallel, on X and Y, respectively. The height of each layer is
about 1.2 m, with a 0.4 m step size for Z-axis and 3 integer dz-units.
5

Side 2
a Side 1
c d
Figure 8. SEM images of representative rinsed silver woodpile structure at
differentdegrees of magnification, for two different sides. Panels (a)-(d) show
close-ups of side 1 and side 2, respectively: (a) 1600, (b) 3125, (c) 6000, (d)
6000.
The images recorded with a magnitude of 12000 and 1m scale confirmed that
silver beams have continuous surface but roughness. This can be, on a hand, a
consequence of the technical “writing” conditions and the chemical system
composition. On the other hand, silver is very reactiv and can undergo chemical
changes in contact with atmosphere. Thus, the electroless plating is the best
manner to prevent the silver corrosion.
(2) TPA silver fabrication
(1) hydrofobic glass
coating surface
6
b
(3) electroless plating
Figure 9. Fabrication process: (1) Hydrophobic coating of the glass slides
t o avoid gold deposition, (2) TPA silver structures fabrication, (3) gold
coating by electroless plating.
A uniform and smooth gold coating of the silver structures is achieved when
using a 0.1M methanolic HAuCl4 solution. The methanolic HAuCl4 solution

was chosen instead of an aqueous one because it generates less porous and
grainy metallic deposits [11]. The reaction was performed at room temperature
and stopped after 4 minutes to avoid the adherence of gold colloids on the
substrate surface.
a b
Figure 10. SEM images of silver structures coated in gold by EP after
4 min(a) and 10 min(b); (c) colloid detail.
Outside of the woodpile we find no change as compared to before the AuCl4
treatment, which shows that the treatment is efficient only in the areas where
Ag was present.
4 Optimisation of gold nanostructures fabrication
Gold is a well-known noble metal, which is not affected by air, moisture,
oxygen, and other corrosive agents, making it well-suited for wide fields
applications. Different techniques using light to fabricate gold nanostructures
were developed because its already known applications in photographic art as
well as for the new applications in nanophotonics and nanoelectronics, as well
as in biology imaging and sensing [12].
Why gold instead of already well-demonstrated efficiency of silver in
photographic art? Gold as metal exhibits a high stability in contact with
atmospheric ambiance.
4.2. UV-Vis investigation
Preliminary experiments were performed in dilute solution in order to validate
the gold ions photoreduction process. In that case UV exposure (one photon)
can be used to validate the process.
Figure 11 a) and b) shows typically UV-Vis spectra recorded after irradiation in
solution and thin film of gold salt and ammonium ferric citrate mixture in PSS,
irradiated at every 20, and 15 minutes, respectively.
7

Figure 11. Evolution of the UV absorption spectra of an aqueous solution
containing 1 mMol Au(III), 1 mMol Fe(III)-citrate and 1 mL PSS upon irradiation:
a) in solution, at every 20 minutes; b) in thin film, at every 15 minutes.
Upon irradiation a plasmon band clearly appears (Figure 11a) indicating the
generation of gold nanoparticles. The gradual increase of this band and the red
shifted plasmon peak position represent the growth of the gold particles in
solution. As expected, this phenomenon is coupled with the decrease of the
Au(III) band located at around 310 nm, assuming that the Au(III) ions are
reduced upon irradiation. In the solid state, similar spectra can be observed.
Nevertheless as diffusion of active species is much slower than in solution,
after similar time of irradiation (an hour), the plasmon band is less broad and
located at lower wavelenght around 550 nm.
Figure 12. UV spectrum recorded for the mixture containing 1 mMol
Au(III), Fe(III)-citrate and 1 mL PSS upon irradiation at the same irradiation
times in thin film, at 1:2 ammonium ferric citrate:gold salt ratio.
4.3. The gold structures fabrication process
8

Our goal is to develope a lasser asisted technique to fabricate continuous
and well defined gold nanostructures inspiring by the iron-based photographic
technique in gold and its photochemical process.
Taking in account that the process has been validated both in solution and in
the solid state, preliminary two-photon induced photoprecipitation experiments
have been performed.
4.3.1. PSS- matrix for gold microfabrication
The TPA iradiation of a gold salt aqueous solution can form gold nanoparticles,
insoluble in water, which aggregate short time after generation. On Figure 44
can be seen the optical image of two huge gold colloids obtained in a 0.1 M
gold salt solution, when irradiating by a femtosecond laser at 40 mW.
Figure 13. Optical image recorded in transmitted light for two huge gold colloids
generated in aqueous solution of gold salt at 40 mW.
The key point of our experiment was to increase the solution viscosity using
different matrices such as xanthane, polyethyleneoxide, gelatine, and poly (4styrenesulfonate
acid) as stabilizers. These compounds allow to controll the rate
of reduction and to keep the metallic deposition localized in the small volume
at the focal point during the laser action and after it stops. From this point of
view is required a hydrosoluble and relative chemical stable polymer host, good
electrons donor which allow an homogeneus dispersion of high gold salt
concentrations without phase separation in the solid state. In this respect we
chose the poly (4-styrenesulfonic acid), denoted PSS, which embodies all these
properties, as a system stabilizer.
Thus, it offers the possibility to fabricate continuous and well defined silver
nanostructures by two-photon absorption. Figure 14a) shows gold lines
fabricated by TPA at the same laser power when PSS matrix is added to the
previous gold salt aqueous solution.
9

a b
Figure 14. Gold lines fabricated by laser in thick film of: a) a PSS aqueous
solution of gold salt at 30 mW; b) a PSS, gold salt and ammonium ferric citrate
aqueous solution of in 40-50 mW range.
It is therefore important to study the photochemical reactions of gold salt in
polymer matrices. Thus, we created a chemical system that contains
tetrachloroauric acid as active specie and ammonium ferric citrate as sensitiser,
dispersed into a PSS matrix. The structures are thiner and more regular by
adding of sensitizer and required less energy to be written, as can be seen in
Figure 14b.
That means PSS induces the decrease of size and number of the nanoparticles
generated by photoreduction by reducing the reaction rate. The contribution of
the polymer film in the photoreduction reaction is not yet elucidated.
4.3.2. Double-line effect in thin PSS matrix
The TPA photoreduction process in thin films allows us to fabricate various
kinds of 2D structures such as nanodots and nanowires networks. Within our
research we have studied the fabrication of metallic wires with dimensions
varying from a few hundred nanometers to one micron for their widths, and
ranging from a few to several hundred microns for their lengths (see figure
15a).
a b
10

Figure 15. a Optical image of gold wires network in polymer matrix, b)
SEM image of two double wires after removing the unreacted matrix
There are two main aspects which allow a clear description of a “double-wire”
characteristic: the size of the wire, denoted wire width, and the double-wire
separation distance, denoted distance between lines.
For comparison, atomic force microscopy (AFM) measurements were
performed in order to establish the 3D aspect of the metallic wires (Figure 16).
2.0µm
Z[nm]
z [nm]
600
500
400
300
200
100
0
0 0.5 1 1.5 2 2.5 3 3.5 4 5
x[m]
X[µm]
11
Distance
between lines
Wire width
Figure 16. AFM measurements of a typical gold double-wire: a) topographic
view, b) cross-section along the double wire, c) 3D view
A topographic AFM view is shown in the left images of Figure 16a) and a
cross section along them is plotted at the centre, in Figure 16b). Each metallic
wire has a full width at half maximum of 600 nm with a height of 500 nm. A
3D view is shown on the right images. As it can be seen, regular and
continuous metallic wires can be fabricate, their walls being almost vertical
[10].
At the first estimation it can be assumed that the metal deposition does not
occur at the center of the laser beam, but on its outer diameter. In fact, there is
about more complex phenomena that occur during the gold wires fabrication.
How can we control the cluster generation, and further the growth of
metallic structures, when the energy provided by laser irradiation is
considerably lower than the UV one but highly localized within the gold salt-
doped matrix?
The fabricated lines are very sensitive to the writing conditions.
At low laser power the lines are thin and show granular structure, as shown in
Figure 17(a). On the contrary, at higher power the lines are regular, but exhibit
a double-wire shape due to the ablation process, which occurs immediately
after laser interaction with gold nanoparticles previously formed – Figure 17(b).
We may admit that the size of nanoparticles that act as nucleation centres is
another parameter which influences the evolution of fabrication process. The
morphology of patterns undergoes a spectacular change if the laser power and
the critical exposure time are oversized, due to a novel ablation process.

In fact, this unusual phenomenon is caused by the collective action of multiple
pulses.
Nucleation
10 mW 20 mW
12
40 mW
Growth
a b
Nucleation
40 mW
Figure 17. Competition between (a)nucleation and (b) growth processes
during the gold fabrication at different laser power
4.3.3. The influence of the operating parameters
The deposition of gold nanowires is performed at the active layersubstrate
interface in order to recover the metallic deposit at the substrate surface after
removing the unreacted matrix.
The chemical reaction path of the salt-PSS-ferric citrate system is expected to
be dependent on the initial molar ratios between reactants and on viscosity of
solutions, on the reaction parameters, such as laser power and nature of the
substrate used for the active layer deposition.
4.3.3.1. The laser power
The delivered power of femtosecond laser was varyed in order to establish how
it can modify the characteristics of double nanowire. Typical laser powers are
in the tens of milliwats, measured at the laser output.
Under our experimental conditions, no gold lines were observed for laser
powers below 10 mW.
Higher laser powers, ranging from 30 to 40 mW, are required to initiate the
process for other metals such as silver, copper or nickel. This can be attributed
to a higher reactivity of gold (III) ions (oxidative power) when compared to
others metallic ions.
There were obtained similar structures as shape, but various as size, at two
different powers of the laser (80 mW and 120 mW), the results suggesting that

the power as parameter exhibits a major influence among the double-line
characteristics. Vertical line is wider and broader than the horizontal ones by
almost a factor two due to the laser power used-120 instead 80 mW.
Z[nm]
500
400
300
200
100
0
0 1 2 3 4 5 6
X[µm]
13
120 mW
a b c
Figure 18. AFM measurements of typical gold wires for two different powers
80 mW
A top view is shown in Figure 18a and the cross-section plotted along them at
the centre, in Figure 18b. Each metallic wire has a full width at half maximum
of 600 nm with a height of 500 nm, whereas distance between lines records a
considerable increase at the bigger laser power. All experimental data are in
good agreament with the prior predicted behaviour of double wire generation.
A 3D view is shown on the right images of Figure 18c). As it can be seen
regular and continuous metallic wires can be fabricate, their walls being almost
vertical.
4.3.3.2. The substrate
To complete this study, we investigated the influence of the substrate nature
among the double wire characteristics. Additionally, was analyzed the
regularity wires shape and the fixing of the metallic deposition on the sample
surface after the unreacted matrix removal.
Thin solid films were prepared by spin-coating first directly onto glass
substrate.
a b

Figure 19. a) Optical image of a metallic wire array ; the wires length is 200
microns, b) SEM image-enlargement of two double wires
When finished the unreacted matrix was removed by rinsing the sample with
alcohol. A partial or complete detachment of wires on the glass surface was
observed due to the weak interaction forces between glass and gold. Below are
presented a few impressive images recorded with different microscopic
techniques:
a b
Figure 20. a) Optical image of gold wires array on an untreated glass support,
after washing, b) SEM image-double wires disconnected from the substrate
Po ly im id e u n d erlay ered glass
The wires adherence can strongly be increased by using a thin polyimide
underlayer (800 nm) deposited on top of the glass substrate. We assume, as
expected, that chemical structure of polyimide allows it to establish strong
coordinative bonds gold-nitrogen with gold wires.
14

a b
Figure 21 a) Optical image of gold nanowires deposited on an polyimide coated
substrate, b) SEM view of two wires of the network
Thus, the wires always remain uniform and straight before as well as after the
washing step. The regular shape aspect of the wires is another positiv point of
the polyimide glass coated surface influence, comparatively with the untreated
glass one. The preservation of wires characteristics is illustrated in Figure 21b).
4.4. The thermal effect
Ablated
polyimide
region
15
Polyimide
underlayer
Gold nanowire deposition
on polyimide layer
a b
Figure 22. AFM measurements of a typical double line: a) 3D view of a two double
lines fabricated with 60mW and 65 mW; b) detail of 3D view of the double line at 60
mW
The profile of a double line can be seen below:
Figure 23. AFM profile for the fabricated line (Cross-section)
4.5 The overcoming of the thermal effect
The nucleation and growth experiment, associated with absorption spectra in
solid state, suggested us an "optimum" of experimental conditions which can
lead to good quality lines without ablation. For our case a laser power of 15

mW and gold salt concentration of 2.510 -5 M proved to yield the best quality of
the structures.
4.5.1 Nanodots
Instead of lines it is possible to obtain dots when the laser spot is not moved
during the fabrication but remains at the same place.
Figure 24 shows typical AFM measurements for a single nanodot, here with
350 nm diameter and 119 nm heights. It has been fabricated at 25 mW laser
power, with an exposure time of 5s and a gold salt concentration of 2.5·10 -5 M.
a b c
Figure 24. A gold nanodot fabricated at low laser power and gold concentration:
a) top-view; b) 3D view; c) cross-section
4.5.2. Single wires
Figure 25(a) presents a serie of gold lines, fabricated in fresh thick film, with
respect to “optimum” conditions presented above.
a b
Figure 25. Optical images of one-single gold wires deposited in thick film,
recorded in transmitted light: (a) in polymer matrix; (b) surrounded by air,
after washing process.
16

4.5.3. 3D structures
The 3D structure was written in a thick film with a thickness estimated at
30m, using a 100xPh3 immersion-oil objective lens to deliver 15 mW to the
sample. It is important to mention that the actual transmission of the optical
microscope set-up between laser output and the focal point is 43%. That is to
say that a given 15mW output of laser corresponds to 6-7mW sent at the focal
point within the material.
a b
Figure 26. Optical images of a 3D woodpile with a period of 2.5 m, 7x7 lines
per layer and 20 m height: (a) in transmitted light with x100 oil-immersion
objective; (b) in dark-field with x20 objective.
The woodpile-like structure is a quadratic prism, with 15 m width of base
along x and y axis, and 20 m total height. The three-dimensional object
consists of 10 layers. Each layer contains 7 parallel lines with a period of 2.5
m, which are oriented alternatively, on X and Y, layer by layer. The height of
each layer is about 2 m, with a 0.2 m step size for Z-axis and 10 integer dzunits.
17

6. Conclusions of part B
In this work, we developed and optimized a direct and versatile pathway to
fabricate metallic structures based on a metallic photo-reduction process
induced by femtosecond laser irradiation.
The fabrication process is very sensitive to the „writing” conditions, the
chemical composition of the active layer as well as the laser power are found to
have a strong influence on the fabricated structures.
Continuous and regular metallic wires have been obtained in repeatedly and
reproducible way. AFM and SEM measurements show that gold and silver
wires are in fact constituted by two metallic lines –double-wire shape- centered
on the area of engraving and generated by the thermal effect.
The origin of the double-wire shape of the metallic wires has been
demonstrated and we showed that optimized experimental conditions allow to
generate a metallic single wire deposition.
This method allowed us to fabricate regular and well-defined 3D gold
microstructure embedded in a dielectric matrix as well as 3D self-standing
silver microstructure.
Optical and spectroscopic investigations highlighted that the metallic
structures obtained by us exhibit very important plasmon resonances showing
promising optical properties and challenging applications.
This direct writing technique may be useful to fabricate highly efficient 3D
gratings with spectral filtering properties due to the significant index contrast
between polymer host and metallic parts.
19

Selected References
1. E. S. Wu, J. H. Strickler, W. R. Harrell, W. W. Webb, “Two-photon
lithography for microelectronic application”, The Proceedings of SPIE 1992,
1674, 776-782.
2. S. Maruro, O. Nakamura, S. Kawata, “Three-dimensional microfabrication
with two-photon-absorbed photopolymerization”, Optics Letters 1997, 22, 132-
134.
3. P.-W. Wu, W. Cheng, I. B. Martini, B. Dunn, B. J. Schwartz, E.
Yablonovitch, “Two-Photon Photographic Production of Three-Dimensional
Metallic Structures within a Dielectric Matrix”, Advanced Materials 2000, 12,
1438-1441.
4. C. A. Sacchi, “Laser-induced electric breakdown in water”, Journal of
Optical Society of America B 1991, 8, 337-345
5. F. Stellacci, C. A. Bauer, T. Meyer-Friedrichsen, W. Wenseleers, V. Alain,
S. M. Kuebler, S. J. K. Pond, Y. Zhang, S. R. Marder, J. W. Perry, “Laser and
Electron-Beam Induced Growth of Nanoparticles for 2D and 3D Metal
Patterning”, Advanced Materials 2002, 14, 194-198.
6. J. L. Elechiguerra, L. Larios-Lopez, C. Liu, D. Garcia-Gutierrez, A.
Camacho-Bragado, and M. J. Yacaman, “Corosion at the Nanoscale: The Case
of Silver Nanowires and Nanoparticles”, Chemistry of Materials 2005, 17,
6042-6052.
7. B. P. Donat, S. Panozzo, J. C. Vial, C. Beigne, R. Rieutord, “Increased field
effect mobility from linear to branched tiophene-based polymers”, Synthetic-
Metals, 2004, 146, 225-231.
8. S. J. Henley, J. D. Carey, S. R. P. Silva, “Laser-nanostructured Ag films as
substrates for surface-enhanced Raman spectroscopy”, Applied Physics Letters
2006, 88, 1-3.
9. L. Rivas, S. Sanchez-Cortes, J. V. Garcia-Ramos, G. Morcillo, “Growth of
silver Colloidal Particles Obtained by Citrate Reduction to Increase the Raman
Enhancement Factor”, Langmuir 2001, 17, 574-577.
10. N. Tosa, G. Vitrant, P. L. Baldeck, O. Stephan, S. Astilean, I. Grosu, “Twophoton
laser deposition of gold nanowires”, Journal of Optoelectronics and
Advanced Materials 2007, 9, 641-645.
11. R. F. Karlicek, V. M. Donelly, G. J. Collins, “Laser-induced metal
deposition on InP”, Journal of Applied Physics 1982, 53, 1084-1090.
12. a) A. N. Shipway, E. Katz, I. Willner, «Nanoparticle Arrays on Surfaces for
Electronic, Optical, and Sensor Applications», ChemPhysChem 2000, 1, 18-25;
b) K. Aslan, J.R. Lakowicz, C.D. Geddes, «Plasmon light scattering in biology
20

and medicine: new sensing approaches, vision and perspectives», Current
Oppinion in Chemical Biology 2005, 9, 538-544.
13. T. Baldacchini, A.-C. Pons, C. N. LaFratta, J. T. Fourkas, Y. Sun, M. J.
Naughton, “Multiphoton laser direct writing of two-dimensional silver
structures”, Optics Express, 2005, 13, 1275-1280.
List of publications
I. N. Tosa, L. Olenic, I. Bratu, R. Turdeanu, I. Turcu, “Infrared and
UV-Vis Spectroscopic Study of 3,7,10-Substituted-Phenothiazine
Derivatives Adsorbed on Gold Nanoparticles”, Journal of
Physics: Conference Series 2009, 182, 012019, 1-5
II. N. Tosa, A. Bende, R. A. Varga, A. Terec, I. Bratu, I. Grosu, “H-
Bond-Driven Supramolecular Architectures of the Syn and Anti
Isomers of the Dioxime of Bicyclo[3.3.1]nonane-3,7-dione”,
Journal of Organic Chemistry 2009, 74, 3944-3947.
III. N. Tosa, G. Vitrant, P. L. Baldeck, O. Stephan, I. Grosu,
“Fabrication of 3D Metallic Micro/nanostructures by Two-Photon
Absorption”, Journal of Optoelectronics and Advanced Materials
2008, 10, 2199-2204.
IV. N. Tosa, G. Vitrant, P. L. Baldeck, O. Stephan, S. Astilean, I.
Grosu, “Two-photon laser deposition of gold nanowires”, Journal
of Optoelectronics and Advanced Materials 2007, 9, 641-645.
V. G. Vitrant, J. Bosson , N. Tosa , T. Rosenzveig, O. Stephan, S.
Astilean, P.L. Baldeck, “Observation of optical dispersion effects
in metallic nanostructures fabricated by laser illumination of an
organic polymer doped with metallic salts”, Proceedings of SPIE
2007, 6470, 1-9.
VI. N. Tosa, J. Bosson, G. Vitrant, P.L. Baldeck, O. Stephan,
“Fabrication of metallic nanowires by two-photon absorption”,
Scientific Study&Research-Chemistry&Chemical Engineering
2006, VII, 899-904.
VII. N. Tosa, J. Bosson, M. Pierre, C. Rambaud, M. Bouriau, G.
Vitrant, O. Stephan, S. Astilean, P. L. Baldeck, “Optical
properties of metallic nanostructures fabricated by two-photon
induced photoreduction”, Proceedings of SPIE 2006, 6195, 1-8.
21

VIII. J. Bosson-Ehoomann, A. Mihut, N. Tosa, S. Astilean, M. Pierre,
C. Rambaud, L. Vurth, P. Baldeck, O. Stephan, „Two-Photon
Fabrication of Metallic Nanowires for Plasmonics”, Nonlinear
Optics and Quantum Optics 2006, 35, 195-200 .
IX. A. Mihis, N. Tosa, L. Drule, „Synthesis of Some Compounds
having 1,3-Dioxane Rings with Liquid-Cristalline Properties”,
Scientific Bulletin of North University of Baia –Mare 2005, XIX,
185-192.
X. N. Tosa, A. Bende. I. Bratu. I. Grosu, „Theoretical Modeling and
Experimental Study of Intramolecular Hydrogen-bond in
Tetramethyl 3,7-dihydroxybicyclo[3.3.1]nona-2,6-diene-2,4,6,8tetracarboxylate”,
Studia Univ. Babes-Bolyai, Chemia 2005, L,
157-162.
XI. N. Tosa, A. Bende, S. Pînzaru, I. Grosu, E. Surducan, „Structure
and Vibrational Spectra of Tetramethyl 3,7-
Dihydroxybicyclo[3.3.1.]nona-2,6-diene-2,4,6,8-tetracarboxylate
and Bicyclo[3.3.1]nonane-3, 7-dione”, Studia Univ. Babes-Bolyai,
Physica 2004, XLIV, 289-292.
22