Second hyperpolarizabilities of π-conjugated silicon-ring polymers

The longitudinal second hyperpolarizabilities (γzzzz) of several Si-ring polymers are investigated. The γzzzz of oligomers containing up to eight monomer units are calculated by the finite field (FF) method including electron correlation at the level of the Møller-Plesset second-order perturbation theory (MP2) within the framework of the INDO approximation. Polysilole exhibits the largest γzzzz among the polymers investigated. The γ density analysis shows that the γzzzz of all the Si-ring polymers are mainly due to the polarization of carbon π-electrons.