Growth, structural, vibrational, characterization and DFT investigations of 2-methylimidazolium hydrogen oxalate dihydrate (2MIO) single crystal-towards third order NLO applications

Abstract

We report the studies conducted on the single crystal of 2-methyimidazolium hydrogen oxalate dihydrate (2MIO) which was achieved by employing the solution growth technique of conventional slow evaporation wherein the solvent used was deionized water. The confirmation of the grown 2MIO crystal's lattice parameters were accomplished by the analysis of single-crystal X-ray diffraction (SCXRD). The powder sample was utilized for the studies of identifying its crystalline phase, composition, and NLO efficiency. The UV–Vis-NIR studies show that the 2MIO crystal has a better transmittance in the region of entire visible and the lower cut-off wavelength is 280 nm. The decomposition and dissociation points of the 2MIO were studied by employing thermal measurements. The nonlinear optical parameters were computed for 2MIO from the performed Z-scan study. Additionally, quantum chemical studies were carried out on 2MIO molecule which was performed by making use of density functional theory (DFT) at the B3LYP/6–311 G (d.p) method. The optimized geometrical parameters, the bond length and bond angles were compared with the observed experimental XRD data. Hirshfeld surface analysis featuring 2D fingerprint plots were analysed by using Crystal Explorer 3.1 such that it could confirm the intermolecular and weak interactions. Natural bond orbital (NBO) analysis was undertaken to evaluate the donor-accepter interactions and stabilization energies of the molecule. The HOMO-LUMO energy was analysed whereby the energy gap (ΔE) and other related properties of the molecules present in 2MIO were calculated. The first-order hyperpolarizability of 2MIO was measured from the computational studies with which it is established that the obtained value is 4.95 times than that of standard urea.