Synthesis, X-ray diffraction, diferential scanning calorimetry, and magnetic susceptibility studies of a series of binuclear ruthenium(II) carboxylates giving liquid crystalline phases.

L. BONNET; F. D. CUKIERNIK; P. MALDIVI; A. M. GIROUND-GODQUIN; J. C. MARCHON; M. IBN-ELHAJJ; D. GUILLON; A. SKOULIOS

CHEMISTRY OF MATERIALS

American Chemical Society

Año: 1994 vol. 6 p. 31 - 34

0897-4756

  A wide series of diruthenium(II,II) tetracarboxylates of general formula Ru2(RC00)4 was prepared; the carboxylate substituents include linear alkyl chains (R = C4H9 to C19H39), unsaturated chains (R = CH2=CH(CH2)8-, (CH3)2C=CHCH2CH2CH(CH3)CH2-)as well as afluorinated chain (R = C7F15-). An adduct obtained by pyrazine intercalation was also characterized (R = C11H23-). The mesomorphic behavior of these compounds was investigated by differential scanning calorimetry and X-ray diffraction. A thermotropic columnar mesophase was observed above ca. 100 “C for all complexes except the  perfluoro compound and the pyrazineadduct. Unsaturation in the peripheral alkyl chains strongly depresses the transition temperature to the liquid-crystalline phase. The magnetic susceptibility of three members of the series wasmeasured in the range 6-400 K. A rigorous analytical expression of the magnetic susceptibility vs temperature was derived from the (pi* )2(d*)2 electronic configuration for the ground state of a  diruthenium(II,II) core, by applying a spin-orbit Hamiltonian, and the data were successfully analyzed on this basis.