Crystal Engineering with Structurally Flexible 1,1′‐Substituted Ferrocenes for Nonlinear Optical Materials

Cocrystals derived from 1,1′‐bis(ethenyl‐4‐pyridyl)ferrocene (1) and resorcinol/phloroglucinol and a crystal of 1,1′‐bis(ethenyl‐4‐quinolinyl)ferrocene (5) have been studied with the aim of engineering crystalline NLO materials. X‐ray structure analyses revealed a NLO active syn‐type molecular conformation of 1 and 5 via hydrogen bonding with resorcinol/phloroglucinol and π‐π interaction between quinoline rings, respectively. For 5, all molecular dipoles are aligned in the same direction and the SHG efficiency is about 4 times that of urea. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)