Crystal structure, vibrational spectra, optical and DFT studies of poly[bis(L-methionine)-κS:O cadmium (II) di-μ-thiocyanato- κ2N:S; κ2S:N

Abstract

Crystal structure, FT-Raman, IR and UV–vis spectroscopy have been applied to investigate the potential nonlinear optical (NLO) material of [Cd(SCN)2(C5H11NO2S)2]n. Crystal structure of [Cd(SCN)2(C5H11NO2S)2]n shows that the one-dimensional chain is propagated through doubly bridging thiocyanate and l-methionine (C5H11NO2S) acts as terminal ligand. These chains are linked together by mean of NH⋯N and NH⋯O hydrogen bonds. Optimized molecular geometry, atomic Mulliken charges, harmonic vibrational frequencies, energies of frontier molecular orbitals (EHOMO and ELUMO), energy band gap (EHOMO–ELUMO), chemical potential (μ), chemical hardness (η), global electrophilicity index(ω) dipole moment, linear polarizability, and first order hyperpolarizability were calculated by Density functional theory (DFT) using B3LYP method with double-zeta valence (LANL2DZ). The calculated structural parameters (bond lengths and angles) are in good agreement with the experimental XRD data. DFT is also applied to explore the nonlinear optical properties of this material. This compound exhibits non-zero static first hyperpolarizabilities values so it might have microscopic NLO behavior. A detailed interpretation of the vibrational spectra was carried out with the aid of normal coordinate analysis following the scaled quantum mechanical force field methodology. Good consistency is found between the calculated results and experimental data for the IR and Raman spectra.