THE METHYLVIOLOGEN RADICAL-CATION - SYNTH ESIS, CRYSTAL-STRUCTURE ANDAB-INITIO CALCULATIONS OF N,N'-DIMETHYL-4,4'-BIPYRIDINIUM CHLORIDE DIHYDRATE

The title compound has been prepared by the reduction of N,N'-dimethyl -4,4'-bipyridinium dichloride with dilithium tritelluride in dimethylf ormamide solution. It forms deep blue crystal needles, which were char acterized by a crystal structure determination. Space group P na 2(1), Z = 8, 3450 observed unique reflections, R = 0.045. Lattice dimension s at - 70-degrees-C: a = 1707.6(8), b = 2323.9(11), c = 664.6(3) pm. T he N,N'-dimethyl-4,4'-bipyridinium radical cations are planar and form ion pairs in the lattice. The chloride ions together with the water m olecules form an infinite network of hydrogen bridges along the crysta llographic a-axis. The structural parameters of the radical cation are in excellent agreement with ab initio calculations.