Supramolecular Nanoporous Materials and Their Applications

Supramolecular Nanoporous Materials and
Their Applications

Ultrafiltration (separation) by Thin-Film Materials
Volatile Organic Compound (VOC) &
Luminescence Sensing of Supramolecular Thin-
Film Materials (Quartz Crystal Microbalance &
Fluorometer)
Adsorption-Modulated Micropatterned Diffraction
Gratings (Diffractive Photonic Lattices)
Toward Artificial Enzymes & Catalytic Reactors
Cage Formation & Their Applications

Supramolecular chemistry may be defined as
“chemistry beyond the molecule”, bearing on the
organized entities of higher complexity that result
from the association of two or more chemical
species held together by intermolecular forces :
metal-ion coordination, electrostatic forces,
hydrogen bonding, van der Waals interacions,
donor acceptor interactions, etc.
- Supramolecular Chemistry – Concepts and Perspectives (J.-M. Lehn, VCH)

Fujita et al, Chem. Commun.1996, 38, 1535.

53 : 54 (square : triangle)
66:34 20 mmol dm -3
58:42 10 mmol dm -3
47:53 5 mmol dm -3
39:61 3 mmol dm -3
28:72 1 mmol dm -3
Fujita et al, Chem. Commun. 1996, 38, 1535.

4
4
5
Fujita et al, Chem. Commun.
1996, 38, 1535.

4:5 / Square : triangle

Cotton et al, J. Am. Chem. Soc. 1999, 121, 4538.

Hong et al, Tetrahedron Lett. 1998, 89, 873.

Stang et al, J. Am. Chem. Soc. 1998, 120, 9827.

Lehn et al, Angew. Chem. Int. Ed. 1996, 35, 1838;
J. Am. Chem. Soc. 1997, 119, 10956.

Stang et al, J. Am. Chem. Soc., 1995, 117, 8793.

Cotton et al, J. Am. Chem. Soc. 1999, 121, 4538.

Lu et al, Inorg. Chem. 2000, 39, 2016.
Lees et al, J. Am. Chem. Soc. 2000, 122, 8956

Hupp et al, Chem. Mater. 2001, 13, 3113-3125.

Mirkin et al, J. Am. Chem. Soc.
1998, 120, 11834-11835.

Why Nanoscale Porosity
• Separations : ultrafiltration
• Affinity membranes
• Selective VOC sensing
• Aquatic sensing
• Novel catalyst platforms
• Reaction control : surface tailoring

Aluminosilicates (zeolites) :
catalysis, separation, and ion-exchange processes
===> large pores, thermally stable and facilitating
the mobility for small cations
Why nanoporous materails with large pores
===> Giant pores may act as nanoreactors and also
tailoring to get more functional surface
Two obstacles encountered : Material stability
and interpenetration (concatenation)

Molecular Squares
M. Fujita, et.al., Chem. Commun. 1996, 1535.
P.N.W. Baxter, et.al., Chem. Commun. 1997, 2231. P.J. Stang, et.al., Res. Chem. Intermed. 1996, 22, 659.
P.J. Stang, et.al., Organomet. 1996, 15, 904. R.V. Slone, et.al., Inorg. Chem. 1997, 37, 5422.
R.V. Slone, et.al., J. Am. Chem. Soc. 1994,116, 2494.

Applications of Thin Films Based
on Molecular Squares
• Membrane-based transportation (Separation)
• Chemical sensing
•Catalysis

Synthesis of Molecular Squares
Re...Re
OC
Cl
CO
Re
CO
Cl
CO
Re
CO
OC
N
N
7Å
N
N
12 Å
OC
Cl
Re
CO
CO
Cl
Re
CO
CO
OC
N
Bu
Bu
N
14 Å
N
N
Zn
N
N
N
N
20 Å
Bu
Bu
OC
OC
CO
Re
Cl
CO
CO
THF/toluene
+ LL [Re(CO) 3 (Cl)(LL) ]
reflux, N 4 R > 95%
2
Slone et al., Inorg. Chem. 1996, 35, 4096.

Characteristics of Rhenium Squares
• High yield assembly
• High degree of size tunability
• Charge neutral
• Hydrophobic interior
• Formation of channels in the crystals
• Stability in H 2 O in thin film and molecular forms
• Zn-porphyrin squares can be easily modified by
axial ligation

Crystal Structures of Molecular Squares
Crystal structures of the pyrazine and the bipyridine squares show
the presence of channels down the crystallographic c axes.
I4, I4 1 /a,
a = 22.717(16), c = 13.538(5) Å
a = 20.931(5), c = 15.417(2) Å
Slone et al, Coord. Chem. Rev. 1998, 171(1), 221.

Crystal Structures of “Corners”
CO CO
OC
Cl
CO CO
Re N
N
OC
Cl
Re
N
N
N
N
C2/c P2 1 /n
a = 7.417(1), b = 4.326(2), a = 7.126(2), b = 14.658(3),
c = 13.077(3)Å, β = 90.14(1)
c = 21.517(6)Å, β = 98.63(2)
Bélanger et al, Acta Cryst. 1998, C54, 1596.

Modification of Square Cavity
Size/shape and chemical affinity of the square cavity can be
selectively modified by axial binding to coordination sites in the
dipyridylporphyrin ligands forming the edges of the square.

Chemically Tailored Molecular Nanotubules
CO
Cl
CO
CO
Re
N
OC
Re Cl CO
CO
CO
Cl
CO
CO
Re
N
OC
Re Cl CO
CO
N
N
N
N
CO
CO
Re
CO
Cl
N
Re CO CO
Cl
OC
CO
CO
Cl
Re
CO
N
Re CO CO
Cl
OC
N
N
= Tunable unit which alters
binding pocket properties
= Secondary guest within
modified cavity
=
CH 3 (CH 2 ) 3
CH 3 (CH 2 ) 3
N
N
N
Zn
N
N
(CH 2 ) 3 CH 3
(CH 2 ) 3 CH 3

N
N N N N
CN
N
NH 2
N
N
N N N N
O NH 2
O
OH
N N N N N
N
N N
N
Br
N
N
CN
CN
N
N
N
N
N
N
N
N
N
N
N
H
N
N
H
N
N
H
N
O
NH
N
O
O
N
N
O
N
H
O
O
O
O
O
O
O
O
O
O
O
O
N
N
N
N
N
O
O
O
O
O
N
N
CH 3 (CH 2 ) 3
NH N
CH 3 (CH 2 ) 3
N HN
O
O
N
(CH 2 ) 3 CH 3
(CH 2 ) 3 CH 3
O
O
N
O
OH N
O
N
N
N N
Zn
N N
N
N
O
O
O
O
N
O
O
O
O
O
O
O
O
O
O
N
N
N
N
N
O
O
N
O
O
N
O
O
O N
N
O
O
O
N
N
O
O
N
N
N

Chemically Tailored Molecular Nanotubules
OC
OC
CO
Cl
Re
Zn N
O
O
Zn
O
O
Cl
O
O
O
CO
CO
Re CO
Zn
•Alkali metal
ion sensing by
luminescence
OC
OC
CO
Cl
Re
Zn
Zn
Cl
CO
CO
Re CO
Zn
OC
OC
Cl
Re
CO
Zn
Cl
CO
Re CO
CO
OC
OC
Cl
Re
CO
Zn
Cl
CO
Re CO
CO
OC
OC
CO
Cl
Re
Zn
N
NH 2
Zn
NH 2
NH 2
Cl
CO
CO
Re CO
Zn
•Zn 2+ recognition
by diffractive
photonic lattices
H 3 C(H 2 C) 3 (CH 2 ) 3 CH 3
N N
Zn = N
Zn
N
N N
OC
OC
Cl
Re
CO
Zn
Cl
CO
Re CO
CO
H 3 C(H 2 C) 3 (CH 2 ) 3 CH 3

[Re(CO) 3 (Cl)(µ-pyrazine)] 4

[Re(CO) 3 (Cl)(µ-porphZn)] 4

Applications of Thin Films Based
on Molecular Squares
• Transportation (Separation)

Permeation Through a Thin Film of the
Porphyrin-based Squares
electrode
Thin films are spin-cast from CHCl 3 solution and are typically
between 100-200 nm thick

Molecular Sieving by Thin Films Based on
[Re(CO) 3 (Cl)(µ-(PorphZn)] 4
SO 3
~ 20 Å
O 3
S
d = 24 Å
N
N
N
Fe
N
N
N
4 -
Re
N
Re
N
N
N
Zn
N
N
Re
Re
10 µA
CH
2
OH
5 µA
Fe
1.2 1.0 0.8
0.6
0.4 0.2 0.0
E vs SSCE (V)
d = 4.5 Å
Bélanger et al, Angew. Chem. Int. Ed. 1999, 38, 2222.

PorphZn Square Modification before Film Casting
Square/TPP K b
= 4 x 10 7 M -1 in CH 2
Cl 2
(Slone et al Inorg. Chem. 1997, 36, 5422.)
Zn
N
Zn
G
Zn
G
=
N
N N
Zn
N N
N
bare electrode
Zn
N
film-covered electrode
d ~ 2.4 Å
I -
200 µ A
d~2.4 A
N
H 3 N
Ru
H 3 N
H 3 N
NH 3
NH 3
d ~ 6.7 Å
1.00
0.75
0.50
0.25
0.00
-0.25
-0.50
E vs SSCE (V)

Snurr et al, Adv. Mater. 2001, 13, 1895-1897.

Applications of Thin Films Based on
Molecular Squares and Rectangles
• Chemical sensing (QCM)

Molecular Recognition and Sensors
+
substrate
receptor
signaling unit receptor substrate
The basic principle of molecular
recognition : for any given substrate,
a receptor possessing geometrical
(structural) and bonding (chemical)
features for specific interactions can
be designed.
Assembling a receptor, a spacer, and
a signaling unit makes a sensor.

VOC Detection Via Quartz Crystal
Microbalance
Sauerbrey Relation
∆Frequency = -C f (∆ Mass)
C f α density and sheer modulus of quartz
Gas tight chamber
VOC (analyte)
AC
QCM crystal modified with a thin film of
mesoporous host material

QCM Study of Benzene Inclusion in
[Re(CO) 3 (Cl)(µ−pyrazine)] 4 Films
0
Blank Substrate
∆ Frequency (Hz)
-20
-40
-60
Square Film
Corner Film
0 150 300 450 600
Time (seconds)
Keefe et al, Langmuir, 2000, 16, 3964.

Aromatic vs. Aliphatic Vapor Inclusion in
Films of [Re(CO) 3 (Cl)(µ-pyrazine)] 4
0.18
Fractional Occupancy
0.12
0.06
benzene
cyclohexane
0.00
0.0 0.2 0.4 0.6 0.8 1.0 1.2
Concentration (mM)
Henry's law : Θ = K b *[guest], at low concentration region

Substituent Effect on VOC Inclusion in Films
of [Re(CO) 3 (Cl)(µ-pyrazine)] 4

2
Synthetic Route to Bisbenzimidazolate-Based
Rectangles
(Third Generation)
OC
OC
O
C
M
Br
C O
CO
+
N
N
K
K
N
N
RT
CH 2 Cl 2 , N 2
O
C
O
C
OC M CO
N N
N N
OC M C O
C
O
C
O
+ 2KBr
O O O O
C C
C C
OC M N
N M− CO
N N
N N
N N
N N
OC M N
N M C O
C C
C C
O O
O O
THF, N 2
M=Re, Mn
N
N
-
Benkstein et al, Angew. Chem. Int. Ed. 2000, 39, 2891.

ORTEP of the Re-BiBzIm/bpy Rectangle
Cavity size: 5.7 x 11.6 Å (defined by the Re atoms)

Space Filling Representation of the Packing
Alignment of the Mn-BiBzIm/bpy Rectangle

Affinity Constants of Thin Films of the Mn-
BiBzIm/bpy Rectangle and a Representative
Square For Selected Volatile Organic
Compounds
VOC
Mn-BiBzIm/bpy
Rectangle
[Cl(CO) 3 Re(µ-pyrazine)] 4
Square
Toluene 3200±1900 332
4-Fluorotoluene 1400±360 200
Benzene 740±250 157
Fluorobenzene 420±80 87
Hexafluorobenzene 460±110 47

Applications of Thin Films Based on
Molecular Squares
• Chemical sensing (Fluorometer)

Sun and Lees, J. Am. Chem. Soc. 2000, 122, 8956.

Applications of Thin Films Based
on Molecular Squares
• Chemical sensing (Diffractive Photonic Lattices)

Diffraction!
I 0
n film I 1
I 0
n surr
I 1
Any periodic pattern featuring
alternating regions of high and
low refractive index is capable
of diffracting electromagnetic
radiation of the wavelength
comparable to the pattern
element spacing.
Diffraction efficiency (DE)
DE depends on the degree of refractive index contrast between
the patterned material and the surrounding medium.

Diffractive Photonic Lattices : The approach is based
on the diffraction efficiency concept
n>1
2
n1 = 1
n 2’ > n 2
’
n2
analyte=
n1 = 1

Direct Patterning of Sensor Elements
Micromolding in Capillaries (MIMIC)
Creation of PDMS
stamp
PDMS
Master
Solution casting
of sensor material
PDMS
Sensing Material
Mold filling by
capillary action
PDMS
Removal of PDMS
stamp leaving behind
micromolded film
Hupp et al, Angew. Chem. Int. Ed. 2001, 41, 154.
75 µm
AFM image

AFM image
Fraunhofer Diffraction Efficiency
He:Ne laser
micropatterned film
(porphyrin grating)
diffraction
pattern
I 0
I 1
10 µm
DE ~
I 1
I 0
x constant

Control Box

Refractive Index
n(x,λ) = n(x,λ) + ik (x,λ)
n(x,λ) --- the complex index of refraction
n(x,λ) --- the real component of refractive index
~ molecular adsorption
k(x,λ) --- the imaginary component of refractive index
(absorptivity of the film material)
~ absorptivity modulation
Correlation between n(x,λ) and k(x,λ) : Kramers-
Kronig relation - “ off-resonance & resonance ”

EtOH uptake by porpZn square functionalized with
pyridyl-ethyleneglycol detected by grating technique
I1 X 100
Io X 6
∆

∆
θ
Plot of ∆DE v.s. concentration of various VOCs for empty porpZn
squares (left) and the comparison of θ and QCM results from benzene,
pyridine and dioxane uptake (right)
pyridine ∆DE (%) values/2.3859
pyridine θ values (QCM)
benzene θ values (QCM)
benzene ∆DE (%) values/2.3859
dioxane ∆DE (%) values/2.3859
dioxane θ values (QCM)
Concentration of VOCs (mM)
Concentration of VOCs (mM)

SIZE EXCLUSION : 1,3,5-tripyridyl-2,4,6-triazine uptake by porpZn square (pink)
and functionalized with TPP (green) detected by grating in water (L) or hexanes (R)
3
10
∆DE (%)
0
N
∆DE (%)
5
0
N N
N
N
N
-3
0 2500 5000 7500 10000 12500
Time (sec)
-5
0 2500 5000 7500 10000
Time (sec)

Direct Patterning of Sensor Elements
Micromolding in Capillaries (MIMIC)
Poly(4-vinylphenol) =
CH 2 CH
n
Creation of PDMS
stamp
PDMS
Master
OH
Solution casting
of sensor material
PDMS
Mold filling by
capillary action
PDMS
Removal of PDMS
stamp leaving behind
micromolded film
Hupp et al, Proc. Electrochem. Soc. 2001, 18, 511-520.
75 µm

VOC uptake poly(4-vinylphenol) films detected by grating technique
* Poly(4-vinylphenol) : ( -CH-CH 2 - ) n
∆
OH
∆

Concentration-dependent uptake study of 2,4,5-Trichlorophenol
(TCP) by poly(4-vinylphenol) in H 2
O detected by grating technique
∆
∆
Cl
Cl
OH
Cl
( -CH-CH 2 - ) n
OH

Incident Wavelength Effects
η(
λ)
2.3OD(
λ)
πd
= exp[ − ]( ){ ∆k(
λ)
cosθ
λ cosθ
2
+ ∆n(
λ)
2
}
Kramers-Kronig expression
∆n(
ω'
)
=
c
π
∞
∫
0
∆α(
ω)
2
ω − ω'
2
dω
OD: optical density
k: absorptivity
n: real component of the refractive index
d: grating thickness
θ: Bragg angle
α: absorption coefficient (α = 4πk/λ)
ω: optical frequency (ω = 2πc/λ)
ω’: the optical frequency of interest for ∆n evaluation
Schanze et al, Langmuir, 2000, 16, 795.

Direct Patterning of Sensor Elements
Micromolding in Capillaries (MIMIC)
OC 10 H 21
Creation of PDMS
stamp
PDMS
Master
N
N
C 10 H 21 O
Solution casting
of sensor material
PDMS
Mold filling by
capillary action
PDMS
Removal of PDMS
stamp leaving behind
micromolded film
75 µm
Tzeng et al, Proc. Electrochem. Soc. 2001, submitted.

Sensor Materials Based on Functional Polymers
OC 10 H 21
N
N
C 10 H 21 O
Free functional polymers (bpy, phen...)---Partially conjugated
ML n
ML n
[ML n ]
N
ML n
Wasielewski et al, J. Am. Chem. Soc. 1997, 119, 11.
N
[ML n ]
Monodentate coordination
Deconjugated (minor)
NEt 3 or CN -
N
N
[ML n ]
Didentate coordination
Fully conjugated (major)
Free polymers

M 2+ (20:80 H2O/EtOH) binding by poly-bpy polymer film and its de-bound study
while addition of NEt 3 detected by grating
∆

M n+ (20:80 H 2
O/EtOH) binding of poly-bpy film detected by grating technique
∆
Zn 2+ :
Pd 2+ K +
∆
∆
Zn 2+
543 nm (green)
633 nm (red)
∆

Applications of Thin Films Based
on Molecular Squares
• Catalysis (Epoxidation)

Toward Artificial Enzymes and Membrane
Catalytic Reactors
Cytochrome P-450
J.R. Cupp-Vickery and T.L. Poulos, 1995
Nguyen et al, Angew. Chem. Int. Ed. 2001, 40, 4239-4242.

A Target Reaction: Olefin Epoxidation
R 2
R 1 + [O]
"enzyme"
Progress:
• catalyst stabilization - > “quasi-immortality”
• induction of size selectivity
• tuning of size selectivity
x y
• induction of modest enantioselectivity L
• discovery of catalytic co-factors
Mn
O
R 1 R 2
x y
L Mn
x y
L
Mn
=
N
O
,
O
N ,
O
O
N
O
O
x y
L
Mn
x y
L
Mn
x y
L
Mn

Enzyme are exquisite catalysts for chemical/biochemical
reactions : excellent stability & high selectivity
===> A potent catalytic center & a surrounding protein
superstructure
===> “superstructure”

Supramolecular coordination chemistry approach :
a simple epoxidation catalyst (manganese porphyrin).
Tailorability : rapid & systematic optimization of
catalytic selectivity “encapsulation concept”

R 2
R 3
R 1 R 4
+ Oxidant
R 2
O
R 3
R 1 R 4

n porphyrin “iron heme moiety” / cytochrome P450
a naturally occurring enzyme used in the oxidative
etabolism)
==> degradation (MnP-O-MnP/50 catalytic cycles)

Lifetime :
(a) Catalyst lifetime : 10 mins → 3hrs
==> bound + unbound in a dynamic equilibrium
(b) 1+2 : TON ↑ 10-fold (500) – K~10 6 M -1
(c) 3+2 : TON ↑ 30-fold (1500) – K~10 7 M -1
(d) Dilution for catalyst concentration (1/1000) :
TON ↑ 7000 for 1+2
21000 for 3+2

Encapsulation of epoxidation catalyst 1 with 2 by
directed assembly.

The enhanced stability and enhanced TONs of the
catalyst assemblies [1+2] and [3+2] compared to
the free catalyst 1.

Selectivity (size):
(a) 4-5 : 5 is 3.5-fold less reactive with 1+2 than
with the naked catalyst (standard).
(b) 4-5 : 5 is 7-fold less reactive with 7 than with
the naked catalyst.
(c) 4-6 : 6 is 4-fold less reactive with 7 than with
the naked catalyst.
* Re-N (free rotate to be more flexible than in film)
===> “no enantioselectivity”

Supramolecular complex with a functionalized cavity for
enhanced selectivity in catalytic epoxidation.

The conceptual topological similarity of cytochrome P450 and
a supramolecular encapsulated catalyst assembly ([1+2]).

Conclusion
Demonstrated Electrochemical sieving for a Molecular-
Square Based Thin-Film Material
Demonstrated Affinity to VOCs for a Thin-Film Material
Based on Molecular Squares Detected by QCM
Demonstrated Potential Chemosensing Applications to
VOCs, Halocarbons or Heavy Metal Ions Detected by
Diffractive Photonic Lattices
Toward Artificial Enzymes & Membrane Catalytic Reactors

Cage Formation & Their Applications

Molecular Cages

Nanoreactor

The key step of the exclusive formation of cross-dimer
stems from the selective formation of ternary complex
before irradiation, which is governed by the size
compatibility of the guests with the restricted space of
the cavity.

(285 nm)

There are two possible pathways to the excited
state of the substrate: (i) direct absorption of UV
light by the substrate around its λ max , & (ii) the
absorption of UV light by the cage followed by
energy transfer into the substrate.

To clarify the reaction pathway, the 1•(2) 2 complex
was irradiated by UV light at 290 nm where the
absorption band of 2 is completely covered by that
of the cage. The adduct was formed much less
efficiently. From these results, we suggest that
substrate 2 is directly excited by irradiation, not via
the excitation of the cage followed by energy
transfer.

Fujita et al, Science 2006, 312, 251

Once the reaction is complete, the product
framework is bent at the 9,10-position, cutting off
the host-guest aromatic stacking interaction (step
b). Accordingly, the encapsulated product is
considerably destabilized & smoothly replaced by
incoming reagents (step c → a). In this sense, the
affinity of the host for reactive substrates & the
disaffinity for product is markedly similar to
enzymatic behavior.

Fujita et al, J. Am. Chem. Soc. 2005, 127, 11950.

Fujita et al, Science 2006, 313, 1273.

How might such assemblies be exploited in future
work (1) One major impetus for the industrial
development of fluorous chemistry that fluorous media
might be used in the selective oxidation of methane to
methanol. Small gaseous molecules such as methane
& oxygen are usually highly soluble in fluorous
phases. Methanol, because of its much greater polarity,
might be rapidly scavenged by a nonfluorous phase
before further oxidation could occur. Reactions of such
guest molecules with the fluorous cages are therefore
of particular interest.

(2) The next logical step would be to immobilize a
fluorous oxidation catalyst in the cage interior & treat
the system with a mixture of methane & oxygen.
(3) The highly positively charged cages might also be
attractive for anionic fluorous guests. Because of
toxicity concerns & environmental persistence, several
commercial fluorous carboxylates & sulfonates have
been removed from the market in recent years. It is
possible that they could be scavenged by the fluorous
cages or by second-generation derivatives.

~ 740 nm due to TTF (e-rich) → triazine (e-deficient)
⇒ TTF +. (radical cationic nature)

[(TTF)2] +.
[(TTF +. ) 2
[(TTF) 2 ] +. : 152 mv
[(TTF +. ) 2 : 304 mv

Fujita et al, Angew. Chem. Int. Ed. 2005, 44, 1810.

A-D-A (450 nm)
A-D-D-A (475 nm)
A-D-A (450 nm)

Fujita et al, J. Am. Chem. Soc. 2005, 127, 4546.

Fujita et al, J. Am. Chem. Soc. 2004, 126, 16292.

[(ZnI 2 ) 3 (1) 2 ]⋅5.5(nitrobenzene)}n (2)
triphenylene / cyclohexane
[(ZnI 2 ) 3 (1) 2 ]⋅1.5(triphenylene)⋅2.5(cyclohex)} n (4a)
[(ZnI 2 ) 3 (1) 2 ]⋅1.4(anthracene)⋅2.2(cyclohex)}n (4b)
[(ZnI 2 ) 3 (1) 2 ]⋅(perylene)⋅(cyclohex)⋅1.5(nitrobenzene)} n (4c)
Anthracene (3b)
Perylene (3c)
Triphenylene (3a)

Triphenylene (3a)
Anthracene (3b)
Perylene (3c)
OPPh 3 (3d)
2 & 3b : colorless
4b : deep yellow
4c : deep red
4d : colorless

Single-crystal-to-single-crystal-guest exchange
[(ZnI2)3(1)2]⋅3.3(nitrobenzene)}n (2’)
Contraction Expansion
[(ZnI2)3(1)2]⋅1.5(triphenylene)⋅2.5(cyclohex)}n (4a

In summary, we demonstrate the efficient inclusion
of large guest molecules in the large channel of 2
via single-crystal-to-single-crystal guest exchange.
Our findings demonstrate that interaction strongly
controls the inclusion geometry of the guest
molecules. Such inter-molecular interactions as
characterized by X-ray analysis will be helpful for
design of not only simple inclusion phenomena but
also new physical properties & chemical reactions
within the coordination network.