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A red, semiconducting salt containing TMTSF and T_CNQ crystallizes in the triclinic system, space group P1, with one molecule of each component in a unit cell with the following crystal data: C IoHI2Se4.CI2H4N4, M r = 652.24, a = 8.096(3), b = 10.465(3), c = 6.998 (2)/k, a = 103.78 (2), /3 = 98.49 (3), ~ = 94.91 (3) ° , V = 565.0 (3) A a, D,, = 1.94 (1), D c = 1.92 g cm -3. Intensity data, collected by counter methods on an automated diffractometer operating in the 0-20 scan mode and employing monochromatized Mo Ka radiation (2 = 0.71069/~,, g = 71.2 cm-~), gave 2306 non-zero reflections which were used in the refinement of a standard heavy-atom solution by the full-matrix least-squares method. With fully anisotropic parameters for the nonhydrogen atoms and fixed, isotropic parameters for the H atoms, a final R value of 0.045 was obtained. The structure is composed of stacks of alternating TCNQ and TMTSF molecules positioned about centers of symmetry along the crystallographic c axis and separated by ~3.5 A. Each molecular component is rather planar and the TCNQ molecule is very nearly parallel to and directly centered above and below each adjacent TMTSF molecule and vice versa. The observed stacking pattern yields an excellent approximation to a mixed-stack array whose re-molecular charge-transfer integral is zero. It is estimated from vibrational frequency data and structural considerations that the degree of charge transfer is non-zero and approximately 0.2 e. The non-zero charge transfer is suggested to arise from the admixing of excited-state molecular orbitals within the mixed-stack crystal band.

AIC405166'The oxidation state properties of the compounds biferrocene, 1 ,I '-terferrocene, and 1,l'-quaterferrocene have been investigated using electrochemical techniques. In the polymeric compounds all of the ferrocene groups are oxidizable to ferricenium at distinct potentials. The values of the potentials can be predicted in some cases using ferrocenyl substituent effects. Partial oxidation gives a series of discrete mixed-valence ions. The mixed-valence ions can exist as a series of oxidation state isomers which differ with regard to the site of oxidation. Electron transfer between different oxidation state sites in the polymeric chains is unsyinmetric giving energetically nonequivalent isomers. The unsymmetrical nature of electron transfer is reflected in the properties of intervalence-transfer (IT) absorptions in the near-infrared spectra. The existence of energetically equivalent and nonequivalent oxidation state isomers may also influence such properties as the intensities of I T bands, the presence of statistical effects in measured reduction potentials, and rates of intramolecular electron transfer.

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