Donor-acceptor substituted cyclohexasilanes:: Materials with potential nonlinear optical properties

The dipolar cyclohexasilanes 1-ferrocenyl-4-((2,2-dicyanoethenyl)-phenyl)-decamethyl- cyclohexasilane (1) and 1-ferrocenyl-3-((2,2-dicyanoethenyl)-phenyl)-decamethylcyclohexasilane (2) were synthesized by conventional methods and fully characterized. Electronic absorption spectroscopic studies suggest increased sigma-pi interactions in the cyclohexasilane derivatives when compared to their open-chained analogues. Small but noticeable electron transmission effects via the cyclohexasilanyl group can be derived from cyclic voltammetric data. Significantly increased values of the quadratic hyperpolarizabilities beta in solution for 1 and 2 are shown by preliminary results of measurements using the EFISH technique.