TD-DFT study of the electronic absorption spectra of iron(III) monoisothiocyanate

The electronic structure of the iron(III) monoisothiocyanate complex has been studied using density functional theory (DFT) calculations. Experimental and simulated electronic absorption spectra have been analyzed. The electronic transitions have been identified by means of natural transition orbital (NTO) analysis. The effect of different solvation models (explicit and/or implicit water environment) and position of SO42− ligand versus NCS− ligand upon its geometry and electronic absorption spectrum has been evaluated. Obtained results show that TD-PBE1PBE//PBE1PBE calculation when [Fe(NCS)]2+ complex is explicitly solvated with the SO42− ligand beside the NCS− ligand is in the best agreement with the experimental [Fe(NCS)]2+ spectrum. NTO analysis indicates that the nature of transitions is mainly characterized as ligand-to-metal (LMCT) charge transfer, where NCS− and SO42− ligands are the main ones responsible for the appeared absorbance peaks in the entire spectrum.

It is based on the main results of detailed analysis of DFT and NTO calculations. It was find out that the main peaks appeared in the UV–Vis spectrum of red [Fe(NCS)]2+ complex originates mainly from the LMCT transition, where main electron donors are the NCS− and SO42− ligands.Figure optionsDownload as PowerPoint slide