A novel ruthenium surfactant: electronic spectra, ZINDO analysis and Langmuir-Blodgett studies of trans-dichloro(6,6 '-bis(N-dodecylbenzimidazol-2-yl)-2,2 '-bipyridine)ruthenium(II)

The complex, dichloro(6,6'-bis(N-dodecylbenzimidazol-2-yl)-2,2'-bipyridine) ruthenium(II), Ru(ddbbbpy)Cl-2 was prepared from the reaction of the free l igand and RuCl2(Me2SO)(4). Structural characterization of the compound by H -1 NMR revealed that 6,6'-bis(N-dodecylbenzimidazol-2-yl)-2,2'-bipyridine l igand lies symmetrically about the equatorial plane with the chlorides axia l to each other. The electronic structure of the compound shows several lig and pi-pi* transitions in the ultraviolet and a broad d(pi)-p(pi*) MLCT man ifold in the visible region of the spectrum. A ZINDO/S calculation reproduc es, in some detail, the general features of the electronic spectrum of the title species. The electronic characteristics of the frontier orbitals are analysed. The parent neutral compound shows a fully reversible oxidation wa ve at -0.04 V vs. the Cp2Fe+/Cp2Fe couple in 0.1 M (C4H9)(4)NPF6/CH2Cl2. Th e low temperature (77 K) EPR spectrum of the one-electron oxidized product is typical for a rhombohedrally distorted Ru(III) complex with g values of 2.73, 2.20 and 1.82. Surface analysis of the parent complex as studied usin g Langmuir-Blodgett methods show a typical isotherm from which an area per molecule of 126 Angstrom(2) can be derived. Thin films of the complex were readily transferred to quartz and indium doped tin oxide (ITO) plates. Thin films are conductive as indicated by the cyclic voltammetry of the complex es on ITO slides.