Synthesis and Crystal Growth of Stilbazolium Derivatives for Second‐Order Nonlinear Optics

A series of ionic stilbazolium salts with benzenesulfonates with different substituents in the para position have been synthesized. Single crystals of 4‐N,N‐dimethylamino‐4′‐N′‐methylstilbazolium p‐methoxybenzenesulfonate (DSMOS) were successfully grown in methanol solution by slow cooling. X‐ray studies revealed that DSMOS crystallized in the triclinic space group P1 with its molecular dipoles perfectly aligned in one direction—favorable for large nonlinear optical and electro‐optical effects. Kurtz powder tests revealed a large powder second‐harmonic generation efficiency that is similar to that of the well‐studied 4‐N,N‐dimethylamino‐4′‐N′‐methylstilbazolium tosylate (DAST).