Role of Anions in Inducing Noncentrosymmetry in 4-Dimethylaminopyridinium Salts for Quadratic Nonlinear Optics

Abstract

A novel organic nonlinear optical material 4-dimethylaminopyridinium l -tartrate dihydrate (DMAPT·2H 2 O) (C 11 H 16 N 2 O 6 ·2H 2 O) was synthesized and characterized by CHN elemental analysis, FT-NMR, FT-IR, and FT-Raman spectral studies. Single crystals of average dimensions 15 × 2 × 2 mm 3 were grown by the solvent evaporation method from an aqueous solution at pH 3.60 at constant temperature (30 °C). The crystal structure was solved by the single-crystal X-ray diffraction method and belongs to the orthorhombic, noncentrosymmetric space group P 2 1 2 1 2 1 with unit cell dimensions of a = 7.2903(5) Å, b = 11.7980(7) Å, c = 16.2981(10) Å, and Z = 4. Thermogravimetry (TG) and differential thermal analysis (DTA) showed that the compound decomposes at 75 °C. The optical transmittance window was found to be 310−1100 nm. The Kurtz and Perry powder test illustrates the phase matching property of DMAPT·2H 2 O, and the powder second harmonic generation efficiency is 1.13 times greater than that of KDP. The laser induced surface damage threshold for the grown crystal was measured as 9.72 GW/cm 2 with a Nd:YAG laser assembly.