CHALCOGENS AS ELECTRON-DONORS FOR SELECTED NONLINEAR OPTIC PHORES

Three different heteroaromatic charge transfer chromophores, e.g. dono r(D)acceptor(A)-substituted thieno[3,2-b]thiophenes 3 and 4, D-substit uted thieno [2,3-c] pyridinium salts 7 and 2-(2'-thienyl)pyridinium sa lts 10 have been prepared, Alkylchalcogenic ethers were used as D-grou ps. The molecular first hyperpolarizabilities beta were determined by the EFISH method in the case of 3 and 4 and by the HRS method in the c ase of the ionic compounds 7 and 10, Substitution of the ether oxygen atom by sulfur increases markedly the beta value which is not further increased by the higher chalcogens selenium and tellurium.