Nonlinear optical studies of group 10 transition-metal thienyl systems

trans-Square-planar Group 10 metal thienyl complexes were synthesized and characterized. The linear and nonlinear optical properties were studied in solution, the latter by forward degenerate four-wave mixing at 1.064 μm. A strong dependence of the linear and nonlinear optical properties on the metal centre was observed, both the lowest energy absorption wavelength and second hyperpolarizability decreasing down the metal group. Abbenzothienyl analogue of the nickel complex was similarly synthesized and characterized, both structurally and optically. The fused ring is seen to have a favourable influence on the second hyperpolarizability. Polymeric analogues of the two nickel complexes were prepared by copolymerization. The lowest energy optical transitions are substantially higher than those of purely organic analogues and the measured second hyperpolarizabilities compare very favourably, being up to 25 times higher than poly[(3-butyl)thiophene].