ELECTROCRYSTALLIZATION, CRYSTAL-STRUCTURE, AND SOLID-STATE PROPERTIESOF HALOGEN-BRIDGED ONE-DIMENSIONAL COMPOUND, ([NI(EN)(2)BR](CLO4)(2))(INFINITY) HAVING AN ELONGATED NI-CENTER-DOT-CENTER-DOT-CENTER-DOT-NI DISTANCE

Two crystal forms (alpha and beta) of a novel halogen bridged one-dime nsional Ni-III-Br-Ni-III compound, {[Ni(en)(2)Br](ClO4)(2)}infinity (e n=C2H8N2), have been prepared by electrochemical oxidation. X-ray crys tal structure analysis of the or form revealed that a bridging Br ion is located on the midpoint between two Ni atoms and the Ni-Br distance of 2.640(1) Angstrom is significantly elongated by introducing a bulk y ClO4- ion as a counter anion. An average Ni-Br distance of 2.693(2) Angstrom for the beta form can be estimated from the lattice parameter along the chain. X-ray photoelectron spectra indicate that both forms have the Ni-III-X-Ni-III structure. Magnetic susceptibility data for both forms show strong antiferromagnetic coupling (J=-1700) between el ectronic spins (S=1/2) localized on the Ni-III on the linear chain.