STRUCTURE AND CONDUCTIVITY OF AN ELECTROCRYSTALLIZED RUTHENIUM [1,8]BINAPHTHYRIDINE COMPLEX

For the first time, the crystal structure of a Ru-II binaphthyridine c omplex and that of its corresponding one-electron reduced product are reported. Reductive electro crystallization of [Ru(binap-2)(3)](PF6)(2 ) (1, where binap-2 = 3,3'-dimethylene-2,2'-bi[1,8]naphthyridine) from an acetonitrile solution resulted in the formation of dark blue cryst als of the one-electron reduction product, [Ru(binap-2)(3)](PF6) (2) h aving one fewer PF6- per formula unit. X-ray analysis reveals that the reduced complex retains the three-ligand d(6) coordination around the central Ru-II. Based on electrostatic considerations and the position s of the PF6- anions in the lattice, the added electron appears to be delocalized over two nearly equivalent binap-2 ligands in 2, in marked contrast to monoreduced and electrocrystallized [Na subset of (trisbi pyridyl cryptand)](0), in which the electron is localized on only one of the bipyridyl subunits. However, based on the available data, alter native interpretations are possible. The crystal packing diagram of 2 shows several intermolecular pi-pi interactions, with 12 of these bein g shorter than 3.5 Angstrom. In contrast, there are no intermolecular distances shorter than 3.5 Angstrom in the crystals of 1. Two-probe el ectrical conductivity measurements under anaerobic conditions indicate that the crystals of 2 behave as semiconductors with a band gap of 0. 53 eV, while those of the unreduced compound are insulating. This repr esents the first molecular semiconducting material with the potential for bidimensional behavior of its kind.