Publications by authors named "Christopher L Heth"

A series of thiophene-fused nickel dithiolene complexes have been prepared via synthetic methods which allow the addition of peripheral aryl groups to the fused thiophene of the dithiolene ligand, thus providing access to a range of structural and electronic modifications to the dithiolene core. X-ray structural studies of the anionic complexes show that the peripheral aryl rings lie in near-perfect coplanarity to the dithiolene core and can form π-stacked columns with N-methylpyridinium cations. Density functional theory calculations show significant delocalization of the frontier orbital electron density into the peripheral aryl rings.

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A series of thieno[3,4-b]pyrazine-based oligomers were synthesized via Stille cross-coupling as models of electronic structure-function relationships in thieno[3,4-b]pyrazine-based conjugated materials. The prepared oligomers include two oligothieno[3,4-b]pyrazine series from monomer to trimer, as well as a series of mixed terthienyls in which the ratio of thieno[3,4-b]pyrazine to either thiophene or 3,4-ethylene-dioxythiophene has been varied. The full oligomeric series was then thoroughly investigated via photo-physical and electrochemical studies, along with theoretical calculations, in order to correlate the effect of conjugation length and oligomer composition with the resulting electronic and optical properties.

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Pressure-dependent X-ray diffraction studies reveal the bulk modulus and compression anisotropy of the 2D magnet [Mn(TCNE)(NCMe)(2)]SbF(6). The Raman response of this and the similar [Fe(TCNE)(NCMe)(2)]FeCl(4) layered magnet, shows that the evolution of the a(g) ν(C=C) frequency correlates well with the magnetic exchange and T(c) variations of these materials under pressure. There is a significantly more complex correlation between the a(g) ν(C≡N) frequency and T(c) despite the fact that some unpaired π* electron density (~0.

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The M-[TCNE] (M = 3d metal; TCNE = tetracyanoethylene) system is one of the most interesting classes of molecule-based magnets, exhibiting a plethora of compositions and structures (inorganic polymer chains, 2D layers, 3D networks, and amorphous solids) with a wide range of magnetic ordering temperatures (up to 400 K). A systematic study of vibrational (both infrared and, for the first time, Raman) properties of the family of new TCNE-based magnets of M(II)(TCNE) (NCMe)(2)[SbF(6)] [M = Mn, Fe, Ni] composition is discussed in conjunction with their magnetic behavior and newly reso-lved crystal structures. The vibrational properties of the isolated TCNE(●-) anion in the paramagnetic Bu(4)N [TCNE(●-)] salt and recently characterized 2D layered magnet Fe(II)(TCNE)(NCMe)(2)[FeCl(4)] are also reported for comparison.

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Dithieno[3,2-b:2',3'-d]pyrrole-based terthiophene and quaterthiophene analogues have been prepared from N-functionalized dithieno[3,2-b:2',3'-d]pyrroles (DTPs) via Stille coupling. In order to thoroughly study the structure-function property relationships within these DTP-based oligothiophenes, an oligomer series was prepared that allows for the investigation of a number of structural effects including chain length, thiophene functionalization, and pyrrole N-functionalization. As pyrrole N-functionalization allows the incorporation of solubilizing side chains without the unwanted steric interactions that typically reduce backbone planarity, the effect of the bulk of these side chains on the optical properties in both solution and the solid state has been carefully investigated.

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A number of conjugated polymer systems can be generated via electropolymerization, including polythiophenes and polyanilines. While both have been reported to polymerize anodically via radical coupling, the presence of the aniline nitrogen plays a significant role in the mechanism of electropolymerization. In this study, the electropolymerization mechanism of 3-(N-alkylamino)thiophenes, structural hybrids of thiophene and aniline, is studied utilizing experimental and theoretical methods.

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The preparation of a new conjugated polymer with a low band gap of approximately 0.5 eV has been accomplished via the electropolymerization of acenaphto[1,2-b]thieno[3,4-e]pyrazine.

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