Molecular and crystal structures of a class of push-pull quinonoid compounds with potential nonlinear optical applications

Molecular and crystal structures of three compounds with electron donor-conjugation unit-electron acceptor framework are reported where the conjugation unit is formally a quinonoid ring. Semiempirical quantum chemical calculations indicate large hyperpolarizabilities in these push-pull molecules. Since all the crystal structures are found to belong to centrosymmetric space groups, modifications are necessary for quadratic nonlinear optical applications.