Synthesis, crystal growth, and second-order nonlinear optical properties of new configurationally locked polyene derivatives

Abstract

Five new crystals based on configurationally locked polyene (CLP) structure are synthesized. This series of crystals all consists of a π-conjugated hexatriene bridge between the dicyanomethylidene electron acceptor and the electron donors with strong hyperpolarization. In particular, the acentric 2-(3-(4-phenylstyryl)-5,5-dimethylcyclohex-2-enylidene)malononitrile (PSDCM) exhibits a large powder second-harmonic generation intensity about 0.3 times that of OH1 (a commonly used CLP nonlinear optical crystal), and the mechanism is elucidated by first-principle studies. Single-crystal X-ray diffraction and diffuse reflectance spectroscopy are performed and the thermal properties in PSDCM are characterized.