Spectroscopic and structural investigations of iron(III) isothiocyanates. A comparative theoretical and experimental study.

A combined experimental and theoretical study on the molecular structure and vibrational spectra of [Fe(NCS)](2+) complex in the aqueous solution at the pH∼2 ± 0.1 have been performed. Experimental Raman spectra of the iron(III) isothiocyanate with higher coordination number in the acidic aqueous solution have been analyzed. Molecular modeling of the iron(III) monoisothiocyanate complex was accomplished by the density functional theory (DFT) method using B3LYP and PBE1PBE functionals. Theoretical vibrational spectra of the iron(III) monoisothiocyanate were interpreted by means of the potential energy distributions (PEDs). The influence of different solvation models and position of SO4(2)(-) ligand vs. NCS(-) ligand upon its geometry and vibrational frequencies have been evaluated. The effect of H2O/D2O isotopic substitution on the experimental and calculated Raman spectra of iron(III) isothiocyanates has been examined. Procedures of Raman spectra subtraction have been applied for the extractions of weak and/or obscured Raman signals. As a result, the presence of bound SO4(2)(-) ion and water molecules in the first coordination sphere in the acidic aqueous iron(III) isothiocyanate solution was confirmed. The vibrational assignments for the investigated iron(III) isothiocyanates were proposed here for the first time.

Molecular structure of mercury(II) thiocyanate complexes based on DFT calculations and experimental UV-electron spectroscopy and Raman studies.

In this work, we report a combined experimental and theoretical study on molecular structure, vibrational and electronic spectra of [Hg(SCN)n](2-)(n) complexes (where n=2, 3, 4) in the aqueous solution. Molecular modeling of the mercury(II) complexes were done by the density functional theory (DFT) method using B3LYP functional with Stuttgart relativistic ECP 78MWB basis set for Hg and 6-311++G(d,p) basis set for all other atoms. The effect of different solvation models with explicit (ligand) and/or implicit water environment upon its geometry, vibrational frequencies and UV spectrum have been studied. The influence of H2O/D2O exchange on the experimental and calculated vibrational frequencies of studied complexes has been established. The double-peak character of the νHgS vibrational mode of the all analyzed mercury complexes and νCN mode of [Hg(SCN)3H2O](-) complex, respectively, were proposed here for the first time. The formation of four-coordinated Hg(II) complexes with thiocyanate and (or) water ligands was verified.