Synthesis, crystal structures, and second-order nonlinear optical properties of new colorless 4-carbamoylpyridinium benzenesulfonate salts

New colorless salts of 4-carbamoylpyridinium benzenesulfonate derivatives having hydroxy, methoxy or bromo substituent with second-order optical nonlinearity were synthesized. Their x-ray structural analyses have been performed. Intermolecular hydrogen bond formation between sulfonate group and carbamoyl group as well as between carbamoyl groups of adjacent cations were observed in the crystals. Using a simple oriented-gas description, non- diagonal second-harmonic coefficients of the crystal were estimated to be not too far form that of colored N-(4- nitrophenyl)-(L)-prolinol. The easy single crystal growth and good transparency in visible region suggest that they may be applicable as crystals for frequency conversion of conventional laser diodes.