Growth and characterization studies on L-threoninium p-toluenesulfonate monohydrate crystal

Abstract

L-threoninium p-toluenesulfonate monohydrate (LTPTM) (IUPAC name: 1-carboxy-2-hydroxypropan-1-aminium 4-methylbenzenesulfonate monohydrate), a new organic nonlinear optical (NLO) crystal, is grown by solution growth method at room temperature. It crystallizes in monoclinic crystal system with noncentrosymmetric space group P21. Presence of NH3+ and SO3− vibrations in IR and Raman spectra confirms the formation of LTPTM molecule. The 1H and 13C nuclear magnetic resonance (NMR) spectra establish the molecular structure. In the 1H–NMR spectrum of LTPTM, the chemical shift corresponding to H-SO3 (6.57 ppm) of p-toluenesulfonic acid monohydrate is absent. This is due to the fact that the hydrogen in H–SO3 is released and combines with the amine group of l-threonine. This ensures the formation of LTPTM molecule. The O5-H5A…O3 intermolecular interaction is also established by the observed upfield shift of COOH group in LTPTM molecule. The crystal is thermally stable up to 73 °C. LTPTM is transparent from 235 to 1100 nm. The second harmonic generation (SHG) conversion efficiency of LTPTM is 0.77 times that of KDP. Third order nonlinear optical susceptibility (χ(3)) of the title crystal is 1.3035 × 10−7 esu which is higher than some reported NLO crystals.