CRYSTAL-STRUCTURE AND SOLID-STATE FLUORESCENCE OF AN OXOMOLYBDENUM(V)-BENZYLVIOLOGEN ELECTRON DONOR-ACCEPTOR SALT

Solutions containing benzylviologen and the fluorescent oxo-d(1) ion MoOBr4(CH3CN)(-) in acetonitrile slowly deposit crystals of the electron donor-acceptor complex (BV)[MoOBr4(H2O)]Br .CH3CN: C26H27Br5MoN(3)O(2), triclinic, space group P (1) over bar; a = 11.349(1), b = 16.1048(8), c = 18.720(1) Angstrom; alpha = 71.961(5), beta = 76.375(7), gamma = 82.484(6)degrees; Z = 4; R(F) = 0.048, Rw(F) = 0.046 for 4135 reflections and 668 parameters. The two independent Mo complex anions in the structure show Mo = O distances of 1.62(1) and 1.629(9) Angstrom. The fluorescence spectrum of the solid complex is similar in shape and intensity to those of other salts of (MoOBr4)-O-V(H2O)(-) with non-quenching cations. The relatively intense fluorescence of solid (BV)[MoOBr4(H2O)]Br.CH3CN suggests that electron transfer from (MoOBr4)-O-V(H2O)-*((2)E) to BV2+, although slightly favorable thermodynamically, does not compete effectively with its rapid fluorescence.