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

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I-17e I-17f coupling, and in some cases order as ferromagnets with T c values between 12 and 15 K. 115 Many of these compounds also exhibit remarkable conductive properties in the direction of the π-stacking 116 and they have even achieved metallic conductivity with the organic radical I-17f with 3GPa of pressure applied. 117 1.4 Metal Coordination of Radical Ligands 1.4.1 Magnetic Coupling Between Metal Centers When two metal ions are brought into close proximity to one another there will be some communication between the spins of any unpaired electrons associated with each ion and there are two motifs which can be considered. For example if two high spin, d 4 metal ions are brought together such that coupling can occur, then the spins will either align in a parallel fashion giving an overall spin of 4 described as ferromagnetic coupling, or they will be anti-aligned, rendering the compound diamagnetic with an overall spin of 0, described as antiferromagnetic coupling. These interactions can occur via direct exchange, or if the two ions are linked via a closed-shell ligand, a mechanism referred to as super-exchange 118 can also occur, which 34
is quite similar to the spin-polarization discussed earlier. This will result in antiferromagnetic coupling if the two metal orbitals in question are the same as is illustrated in Figure 1-13 although depends on the bonding motif of the molecular system being investigated. Ferromagnetic coupling provides systems which have a non-zero spin ground state and are therefore of interest in the field of molecular magnetism, however if two metal ions couple antiferromagnetically to one another it will give rise to a spin state of zero. Some work, however has investigated what are known as spin-frustrated systems which involve, for example, three manganese centers 119,120 or more such as in clusters 121 or Figure 1-13. Orbital cartoon illustrating the mechanism of superexchange. For two generic metal centers M and a closed-shell bridging ligand L. Figure 1-14. Spin frustration for a triangular system of three spin centers. chains. 122 If we consider two antiferromagnetically coupled manganese ions Mn1 and Mn2 with a coupling constant J Mn1-Mn2 , and then include a third Mn3 which is equidistant from each of the first two such that the coupling constant |J Mn3-Mn2 |= |J Mn3-Mn1 | = |J Mn2-Mn1 |, then the tendency would be for the third ion to couple antiferromagnetically such that each of the values are negative. This is illustrated in Figure 1-14 and describes an impossible situation. 123,124 As this circumvents the natural tendency of these ions, they are anthropomorphized as being frustrated. 35
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1,2,3-Dithiazolyl and 1,2,35-Dithia
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an individual binuclear coordinatio
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weren’t sure about something our
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2.1 General........................
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5.3 Reverse oDTANQ.................
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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 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: aromatic ring not only protects the
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
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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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