Synthesis, Structure, and Physical Properties of Nickel Bis(dithiolene) Metal Complexes, [Ni(dmit)₂], with Highly Polar Cyanine Dyes

Three new compounds were obtained by slow diffusion of [Ni(dmit) 2 ] - (dmit = 2-thioxo-1,3-dithiole-4,5-dithiolato) into 4-(dimethylamino)-1-methylpyridinium [C 1 ] +, 4-[2-(4-(dimethylamino)phenyl)ethenyl]-1-methylpyridinium [C 2 ] +, and 4-[4-(4-(dimethylamino)phenyl)-1,3-butadienyl]-1-methylpyridinium [C 3 ] + . [C 1 ] + [Ni(dmit) 2 ] - exhibits two crystallographic phases ( 1, 2 ) as does [C 2 ] + [Ni(dmit) 2 ] - ( 3, 4 ). The structures have been determined: 1, monoclinic, P 2 1 / c, a = 17.450(2) Å, b = 10.646(1) Å, c = 23.891(2) Å, β = 97.42(1)°, Z = 4; 2, triclinic P 1̄, a = 9.776(1) Å, b = 15.195(2) Å, c = 16.999(2) Å, α = 114.14(1)°, β = 101.84(1)°, γ = 93.40(1)°, Z = 2; 3, monoclinic, P 2 1 / c, a = 9.813(1) Å, b = 11.589(1) Å, c = 24.345(3) Å, β = 93.12(1)°, Z = 4; 4, triclinic, P1̄, a = 13.432(2) Å, b = 16.101(2) Å, c = 6.553(1) Å, α = 99.69(1)°, β = 94.34(1)°, γ = 102.88(2)°, Z = 2; [C 1 ] + [Ni(dmit) 2 ] - ( 1 ) exhibits a conductivity of 1.3 × 10 - 2 S cm - 1 . Due to centrosymmetry, none of the materials exhibits second-order nonlinear optical properties, but the structure of 1 demonstrates that layers of highly polarizable cations can be stabilized in a noncentrosymmetric environment between two-dimensional networks of [Ni(dmit) 2 ] - species.