Studies on crystal growth, vibrational, dielectric, electronic, mechanical and thermal properties of new organic nonlinear optical crystal: 3-nitrocinnamic acid†
Abstract
3-Nitrocinnamic acid (3NCA) was synthesized and its crystals were grown in aqueous solution by slow evaporation solution growth technique. The grown crystal was confirmed by powder XRD studies. The geometry, intermolecular hydrogen bonding, and harmonic vibrational wavenumbers of 3NCA were investigated with the help of B3LYP density functional theory (DFT) methods. The calculated molecular geometry has been compared with the experimental data obtained from XRD data. The assignments of the vibrational spectra have been carried out with the aid of normal coordinate analysis (NCA) following the scaled quantum mechanical force field methodology (SQMFF). Vibrational spectral investigation confirms the formation of cyclic dimers in the crystal, with the carboxyl groups of each acid molecule bonded to those of adjacent molecules. The red shift of the O–H stretching wavenumber is due to the formation of strong O–H⋯O hydrogen bonds by hyperconjugation between the carbonyl oxygen lone electron pairs and the O–H σ* antibonding orbitals. Thermal stability of the grown crystal was examined by recording TGA/DTA. Mechanical strength of the grown material was tested by hardness studies. Second harmonic frequency generation was examined by Kurtz and Perry powder test and it reveals that the relative conversion efficiency is 0.8 times greater than that of urea. The theoretical first order hyperpolarizability value was calculated for the optimized structure.
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