Structural, spectral, quantum chemical and thermal studies on a new NLO crystal: guanidinium cinnamate

Abstract

New organic non-linear optical (NLO) single crystals of guanidinium cinnamate were crystallized by solvent evaporation solution growth technique and the crystal and molecular structure were determined by single crystal X-ray diffraction. The crystal packing is dominated by classical N–H···O hydrogen bonding interactions. Due to deficiency of acceptor atoms compared to the donor sites, two unusual ring R₂ ¹(6) motifs are formed through two N–H···O hydrogen bonds. These ring motifs are further connected through chain C₂ ²(6) or C₂ ²(8) motifs along the b-axis of the unit cell. Further, these chain and ring motifs are cross-linked through another N–H···O hydrogen bond leading to classical ring R₂ ²(8) motif. These chain and ring motifs are interlinked with each other to form secondary ring R₆ ⁶(14)/R₆ ⁶(16) motifs. The molecular geometry of the asymmetric part of the unit cell was optimized theoretically by density functional theory using the B3LYP function with 6-311 + + G(d,p) basis set. The optimized molecular geometry and computed vibrational spectra are compared with experimental results which showed significant agreement. The intermolecular interactions of the title compound were analyzed by the Hirshfeld surfaces. The computed hyperpolarizability values showed that the compound is a good candidate for NLO applications. The chemical hardness, electro-negativity and chemical potential of the molecule were computed by HOMO–LUMO plot. The lower band gap of the frontier orbitals indicates the suitability of fabrication of the material for non-linear optoelectronic applications.