Synthesis, growth, structural, spectral, thermal and microhardness studies of a new hydrogen bonded organic nonlinear optical material: L–valinium p–toluenesulfonate monohydrate (LVPT)

Abstract

A new organic hydrogen bonded material, L-valinium p-toluenesulfonate monohydrate (LVPT), was synthesized and grown as a single crystal by slow evaporation solution growth technique with the dimension of 29 × 7 × 4 mm3. A good X-ray quality single crystal was selected from the grown crop and used for single crystal diffraction study. It reveals that the compound crystallized in a non-centrosymmetric monoclinic space group P21 with two set of molecules in unit cell. The plane of the carboxyl group of the cation is making dihedral angle of 85.4(1)° with the plane of the aromatic ring of the anion. The crystal packing features intricate three dimensional hydrogen bonding network through chain and ring motifs. These hydrogen bonded motifs are observed at x = 0 or 1 and aromatic rings of the cations are stacked at x = 1/2 leading to alternate hydrophilic and hydrophobic layers, respectively, along a-axis of the unit cell. Fourier transform infrared (FTIR) and Raman (FT-Raman) spectral studies have been performed to identify the functional groups. The optical transmittance and the lower cutoff wavelength of the LVPT have been identified by UV–Vis absorption studies. Second harmonic generation test using a laser with wavelength of 1064 nm confirms the nonlinear optical efficiency of the sample as 1.5 greater than KDP. The thermal and mechanical properties of the sample were examined by TG/DTA and Vicker's microhardness tests, respectively. Further, the solid state properties were calculated and found to be better than the known nonlinear optical material KDP.