New Hybrid Materials Combining Nickel Bis(dithiolene) Metal Complexes and Reducible Stilbazolium Cations. A Search for Possible Interplay between Optical Nonlinearity and Conductivity

The synthesis and crystal structure of a new compound of formula (NOMS) + [Ni(dmit) 2 ] - is reported (NOMS + = 4‘-nitro-1-methylstilbazolium, and dmit 2 - = 2-thioxo-1,3-dithiole-4,5-dithiolato). It crystallizes in triclinic space group P 1̄, a = 10.029(1) Å, b = 10.502(2) Å, c = 13.051(2) Å, α = 106.57(2)°, β = 91.62(2)°, γ = 104.65(1)°, Z = 2. (NOMS) + [Ni(dmit) 2 ] - exhibits a powder conductivity in the range of 10 - 6 −10 - 5 S cm - 1, which is similar with that of (DAMS) + [Ni(dmit) 2 ] - [DAMS + = 4‘-(dimethylamino)-1-methylstilbazolium]. Contrary to DAMS +, NOMS + undergoes a reversible reduction process at −770 mV (vs SCE). The second-order nonlinear optical properties of NOMS + are investigated versus DAMS + within the INDO−SOS formalism and versus NOMS 0, using molecular structures obtained from density functional theory (DFT) calculations. The data indicate a reversed charge-transfer process resulting in an enlarged hyperpolarizability after reduction of NOMS + into NOMS 0 .