1,2,3-Dithiazolyl and 1,2,35-Dithiadiazolyl Radicals as Spin-Bearing ...

More documents

Recommendations

Info

diamagnetic and so the observed EPR spectrum arises from a monomer-dimer equilibrium which is established in solution. If one or two of the members of the ring are replaced with the isoelectronic C-R or N, a number of related compounds can be derived as shown in Figure 1-6. The classes including I-16, its selenium analogue I-18 and I-17 are an important part of this work so the focus shall be on these types of radicals. 1.3.2 Trithiatriazapentalenyl (TTTA [I-14a]) Many 1,3,2-DTA radicals such as trithiatriazapentalenyl (TTTA [I-14a]), are found to be monomeric in the solid state; a feature born by fact that they tend to exhibit dimerization energies close to 0 kJ/mol. 22 As a consequence there are quite a few examples of 1,3,2-DTA based radicals with interesting magnetic properties. The SOMOs for these compounds are different that those which we have already examined as there is only one electronegative nitrogen atom to take the majority of the spin density. I-14a SOMO for I-14a 61 The radical I-14a was first reported by Wolmershaeser in 1989 62 and was followed by an EPR study two years later. 63 However, little more attention had been paid until it was reported by Awaga in 1999 that this radical exhibited bistability at room 20
temperature. 64 This was a very important discovery as bistability is a key property in developing new devices for functions such as data storage, switching units and sensors for heat or light. 65 Within a certain temperature regime, compounds which exhibit bistability can exist in at least two different polymorophic forms and the sample history is important in determining which of these will be dominant at a given temperature. Compound I-14a for example exists only as what is called the high-temperature phase when heated above 320 K and exhibits paramagnetic properties, whereas if it is cooled to below 210 K it only exists as the low temperature phase which is diamagnetic. This compound will be revisited in section 1.3 when its copper coordination complex is examined. 1.3.3 Dithiadiazolyl Radicals and Their Selenium Analogues 1.3.3.1 1,2,3,5-Dithiadiaozlyl Radicals (1-16) The class of compounds 1,3,2,4-DTDAs based on the I-15 framework, can be isolated by a quantitative cycloaddition of SNS + with nitriles to give the corresponding heterocyclic, closed-shell cation. 66,67 One of the most interesting features that they exhibit is that they isomerise readily via a rearrangement to give the more thermodynamically stable 1,2,3,5-dithiadiazolyl radical (I-16). 68-70 The SOMO for I-15 has a much larger coefficient on the nitrogen atom between the two sulfur atoms than the nitrogen atom adjacent to the carbon. This is evident from EPR spectroscopy which gives only a three line pattern, indicative of coupling to only one nitrogen atom. 71 By contrast, the SOMO for I-16 is nodal at the carbon atom which places a significantly larger amount of the 21
Page 1 and 2: 1,2,3-Dithiazolyl and 1,2,35-Dithia
Page 3 and 4: an individual binuclear coordinatio
Page 5 and 6: weren’t sure about something our
Page 7 and 8: 2.1 General........................
Page 9 and 10: 5.3 Reverse oDTANQ.................
Page 11 and 12: LIST OF FIGURES AND SCHEMES Figure
Page 13 and 14: Figure 2-12. Magnetic susceptibilit
Page 15 and 16: GLOSSARY OF ABBREVIATIONS ° Degree
Page 17 and 18: K k k B LMCT ls LUMO Kelvin Exchang
Page 19 and 20: LIST OF STRUCTURES I-1 I-2 I-3 I-4
Page 21 and 22: I-16a I-16b I-16c I-16d I-16e I-16f
Page 23 and 24: I-22 I-23 I-24 I-25 exo I-26 endo x
Page 25 and 26: I-34 I-35 II-3 II-4 II-1 xxv
Page 27 and 28: III-2 III-1 III-3 III-4 III-5 III-6
Page 29 and 30: V-7 V-8 V-9 V-10 V-11 V-12 V-13 V-1
Page 31 and 32: Chapter 1 - General Introduction 1.
Page 33 and 34: linear relationship shown in Figure
Page 35 and 36: A plot of χT vs. T is an important
Page 37 and 38: examination of phenyl methylene. In
Page 39 and 40: different atomic nuclei. Qualitativ
Page 41 and 42: 3) 14 and a variety of thiazyl base
Page 43 and 44: with one another with an energy bar
Page 45 and 46: magnetic properties and undergoes a
Page 47 and 48: heteroatoms which could facilitate
Page 49: Figure 1-5. Qualitative molecular o
Page 53 and 54: dimerization and therefore a quench
Page 55 and 56: e enough to overcome the energetica
Page 57 and 58: eaches the lower end of the investi
Page 59 and 60: DTDAs has been to exploit the rearr
Page 61 and 62: 1.3.4 1,2,3-Dithiazolyl Radicals (I
Page 63 and 64: aromatic ring not only protects the
Page 65 and 66: is quite similar to the spin-polari
Page 67 and 68: compound there are many competing m
Page 69 and 70: a b c d e Figure 1-16. a) Nonorthog
Page 71 and 72: would result in non-orthogonal over
Page 73 and 74: platinum center as well as the phos
Page 75 and 76: substantial amount of unpaired elec
Page 77 and 78: I-28 I-29 I-30 The metals manganese
Page 79 and 80: gave a combination of 2 mononuclear
Page 81 and 82: changes related to geometric, chemi
Page 83 and 84: Finally, the last chapter reviews t
Page 85 and 86: (23) Rajca, A. Chem. Rev. 1994, 94,
Page 87 and 88: (53) Azuma, N.; Tsutsui, K.; Miura,
Page 89 and 90: (79) Decken, A.; Cameron, T. S.; Pa
Page 91 and 92: (102) Herz, R.; Leopold Cassella &
Page 93 and 94: (128) Aliaga-Alcalde, N., 2003. (12
Page 95 and 96: Chapter 2 - Structural and Magnetic
Page 97 and 98: 2.2.2 pymDSDA Coordination Complexe
Page 99 and 100: 2.2.3 DTDA Coordination Complexes o
Page 101 and 102:
indicators tend to be very weak str
Page 103 and 104:
In Figure 2-1a, the nickel complex
Page 105 and 106:
2.2.3 Cyclic Voltametry The cyclic
Page 107 and 108:
propensity for intermolecular Se-N
Page 109 and 110:
dimerization motif. One possible ex
Page 111 and 112:
the bridging ligand such that the D
Page 113 and 114:
contacts into four different intera
Page 115 and 116:
e acting as a closed-shell, S = 0,
Page 117 and 118:
2.3.4 [Zn(hfac) 2 ] 2·pymDTDA (II-
Page 119 and 120:
ancillary ligands and the nearly oc
Page 121 and 122:
single molecular unit. Upon closer
Page 123 and 124:
across the entire temperature regim
Page 125 and 126:
2.5 Conclusions and Future Work It
Page 127 and 128:
therefore chain formation. However
Page 129 and 130:
The work presented in this chapter
Page 131 and 132:
736(s), 723(s), 646(s), 632(s), 469
Page 133 and 134:
(0.2023 g, 1.104 mmol) in 30 mL of
Page 135 and 136:
(6) Chattoraj, S. C.; Cupka Jr, A.
Page 137 and 138:
Chapter 3 - 5-oxo-5H-naphtho[1,2-d]
Page 139 and 140:
triethylammonium chloride which was
Page 141 and 142:
3.3.2 Mass Spectrometry A sample of
Page 143 and 144:
3.3.4 X-ray Crystallography Crystal
Page 145 and 146:
a 2-fold screw axis across half of
Page 147 and 148:
number of electrons that this compo
Page 149 and 150:
often generated in situ although wa
Page 151 and 152:
similar to compounds II-1 and II-2,
Page 153 and 154:
3.6 Experimental General All reacti
Page 155 and 156:
Chapter 4 - The Polymorphism of Tri
Page 157 and 158:
4.3 Discussion Prior to the discove
Page 159 and 160:
(derived from angles ranging from 4
Page 161 and 162:
a b c Figure 4-2. Packing diagrams
Page 163 and 164:
polymorphs observed and are therefo
Page 165 and 166:
Chapter 5 5.1 Overview There are se
Page 167 and 168:
success and so a Herz ring closure
Page 169 and 170:
did not immediately precipitate, bu
Page 171 and 172:
Figure 5-2 shows the IR spectra for
Page 173 and 174:
comparison of the infrared data obt
Page 175 and 176:
discussed in section 5.2.2. As the
Page 177 and 178:
ing was formed. One of the nitrogen
Page 179 and 180:
equired to obtain a decent agreemen
Page 181 and 182:
Considerations have been put toward
Page 183 and 184:
chelation pocket is similar to that
Page 185 and 186:
the mixture was filtered to remove
Page 187 and 188:
good spectroscopic handle for this
Page 189 and 190:
spectrum from about 1900 to 400 cm
Page 191 and 192:
doublets of triplets associated wit
Page 193 and 194:
adical, followed by the closed-shel
Page 195 and 196:
completely dry after being under va
Page 197 and 198:
changed substantially after the tra
Page 199 and 200:
The reaction to produce V-15 was qu
Page 201 and 202:
the proton two carbons away next to
Page 203 and 204:
which is parallel to the mean plane
Page 205 and 206:
of the 1,2,3-DTA rings could act as
Page 207 and 208:
mixture was refluxed for 20 h yield
Page 209 and 210:
the heat source was removed and the
Page 211 and 212:
1085(w), 1059(w), 1008(w), 917(w),
Page 213 and 214:
___________________________________
Page 215 and 216:
Crystallography P 2 1 /c a = 9.1678
Page 217 and 218:
Compound Name: 4-(2′-pyrimidyl)-1
Page 219 and 220:
Compound Name: [μ-4-(2′-pyrimidy
Page 221 and 222:
Magnetometry 192
Page 223 and 224:
Crystallography P-1 a = 8.9576, b =
Page 225 and 226:
Compound Name: [μ-4-(2′-pyrimidy
Page 227 and 228:
Magnetometry: 198
Page 229 and 230:
Crystallography: P2 1 /n a = 19.884
Page 231 and 232:
Compound Name: 5-oxo-5H-naphtho[1,2
Page 233 and 234:
204
Page 235 and 236:
206
Page 237 and 238:
MS (EI + ): 208
Page 239 and 240:
Compound Name: 5-chloro-1H-[1,2,5]t
Page 241 and 242:
Compound Name: 3-nitro-1,2-naphthaq
Page 243 and 244:
Compound Name: 3,4-dioxo-3,4-dihydr
Page 245 and 246:
Compound Name: 4,5-dioxo-4,5-dihydr
Page 247 and 248:
Compound Name: 6,6′-dinitro-1,1
Page 249 and 250:
220
Page 251:
222
show all

1,2,3-Dithiazolyl and 1,2,35-Dithiadiazolyl Radicals as Spin-Bearing ...

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?