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

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I-16e I-16f One of the most interesting DTDA based compounds discovered to date is I-16f which has received considerable interest since its discovery in 1995 by Banister et al. 81 They reported that the β-phase of this compound was a spin-canted antiferromagnet ordering at 36 K. 81 Spin-canting antiferromagnetism, also sometimes called “weak ferromagnetism”, arises when the spins of neighbouring units line up such that they are tilted slightly to one side with alternating up/down orientations of neighbouring unpaired spins. The result is that the vector sum of each of their moments provides a unidirectional magnetization. A pictorial representation of this can be seen in Figure 1-9. The small magnetic moment which this produces, rises to 1.5×10 -3 μ B as the temperature Figure 1-9. Pictorial representation of spin-canting. Orientation of neighbouring spin vectors (above) and resultant weak vector of magnetization (below). 26
eaches the lower end of the investigated temperature regime and hysteresis is observed at 1.8 K. The room temperature magnetic study revealed a broad maximum at 60 K indicating a short-range antiferromagnetic interaction prior to the onset of the long-range ordering at 36 K. 82 Interestingly pressure related studies performed on this compound found that increasing the pressure up to 16 kbar resulted in a substantial increase of the ordering temperature up to 64.5 K. 85 It is rather important that spin canted antiferromagnetism can only occur in non-centrosymmetric space groups. The phenomenon arises from the antiferromagnetic alignment of spins on two magnetic sublattices which are not exactly antiparallel. 86 As 1,2,3,5-DTDA based systems are one of the major focal points of this thesis a brief discussion of the methodologies employed for their synthesis is appropriate. These types of radicals have received a lot of attention and this is due, in part, to the ease with which they can be prepared and purified. The procedures used to obtain them are well established 87 and usually call for a nitrile to be reacted with lithium bis(trimethylsilyl) amide and subsequently treated with trimethylsilyl chloride to give the trisilyl amidine. 88 These compounds are usually low melting solids (in the cases of mono DTDAs) and can therefore often be purified by vacuum distillation. These compounds can then be reacted with SCl 2 or S 2 Cl 2 to give the dithiadiazolium cation with a chloride counter ion. The 27
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1,2,3-Dithiazolyl and 1,2,35-Dithia
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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 and 50: Figure 1-5. Qualitative molecular o
Page 51 and 52: temperature. 64 This was a very imp
Page 53 and 54: dimerization and therefore a quench
Page 55: e enough to overcome the energetica
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
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propensity for intermolecular Se-N
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dimerization motif. One possible ex
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the bridging ligand such that the D
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contacts into four different intera
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e acting as a closed-shell, S = 0,
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2.3.4 [Zn(hfac) 2 ] 2·pymDTDA (II-
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ancillary ligands and the nearly oc
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single molecular unit. Upon closer
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across the entire temperature regim
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2.5 Conclusions and Future Work It
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therefore chain formation. However
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The work presented in this chapter
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736(s), 723(s), 646(s), 632(s), 469
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(0.2023 g, 1.104 mmol) in 30 mL of
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(6) Chattoraj, S. C.; Cupka Jr, A.
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Chapter 3 - 5-oxo-5H-naphtho[1,2-d]
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triethylammonium chloride which was
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3.3.2 Mass Spectrometry A sample of
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3.3.4 X-ray Crystallography Crystal
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a 2-fold screw axis across half of
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number of electrons that this compo
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often generated in situ although wa
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similar to compounds II-1 and II-2,
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3.6 Experimental General All reacti
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Chapter 4 - The Polymorphism of Tri
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4.3 Discussion Prior to the discove
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(derived from angles ranging from 4
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a b c Figure 4-2. Packing diagrams
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polymorphs observed and are therefo
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Chapter 5 5.1 Overview There are se
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success and so a Herz ring closure
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did not immediately precipitate, bu
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Figure 5-2 shows the IR spectra for
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comparison of the infrared data obt
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discussed in section 5.2.2. As the
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ing was formed. One of the nitrogen
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equired to obtain a decent agreemen
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Considerations have been put toward
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chelation pocket is similar to that
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the mixture was filtered to remove
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good spectroscopic handle for this
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spectrum from about 1900 to 400 cm
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doublets of triplets associated wit
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adical, followed by the closed-shel
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completely dry after being under va
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changed substantially after the tra
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The reaction to produce V-15 was qu
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the proton two carbons away next to
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which is parallel to the mean plane
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of the 1,2,3-DTA rings could act as
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mixture was refluxed for 20 h yield
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the heat source was removed and the
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1085(w), 1059(w), 1008(w), 917(w),
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___________________________________
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Crystallography P 2 1 /c a = 9.1678
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Compound Name: 4-(2′-pyrimidyl)-1
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Compound Name: [μ-4-(2′-pyrimidy
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Magnetometry 192
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Crystallography P-1 a = 8.9576, b =
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Compound Name: [μ-4-(2′-pyrimidy
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Magnetometry: 198
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Crystallography: P2 1 /n a = 19.884
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Compound Name: 5-oxo-5H-naphtho[1,2
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204
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206
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MS (EI + ): 208
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Compound Name: 5-chloro-1H-[1,2,5]t
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Compound Name: 3-nitro-1,2-naphthaq
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Compound Name: 3,4-dioxo-3,4-dihydr
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Compound Name: 4,5-dioxo-4,5-dihydr
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Compound Name: 6,6′-dinitro-1,1
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220
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222
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1,2,3-Dithiazolyl and 1,2,35-Dithiadiazolyl Radicals as Spin-Bearing ...

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