Complex formation of Sn(II) with L-cysteine: an IR, DTA/TGA and DFT investigation.

The novel complex of Sn(II) with L-cysteine (L-H2Cys) has been synthesized and characterized by elemental analysis, TGA and IR spectroscopy. Vibrational assignment and DFT/PBE0/def2-TZVP ab initio simulation give evidence of cysteine molecule being coordinated to Sn(II) as three-dentate chelating N,O,S-donor ligand. The four Perdew density functionals TPSS, PBE0, PBE, TPSSh have been tested to provide consistency of simulated and experimental IR spectra, the best result is provided by unweighted Hartree-Fock density functionals (PBE, TPSS). On the contrary, the Hartree-Fock weighted functionals (PBE0, TPPSh) provide the most accurate geometry optimization. Unharmonic frequencies are obtained via ab initio vibrational self-consistent field (PT2-VSCF) calculations at DFT/TPSS/Def2-TZVP level, the vibrational assignment of IR spectra has been carried out.