N- and S-bonded thiocyanate copper(II) complexes of 2,6-bis-(benzimidazolyl)pyridine – Synthesis, spectroscopic characterization, X-ray structure and DFT calculations

The paper presents a combined experimental and computational study for two novel Cu(II) complexes of 2,6-bis(benzimidazolyl)pyridine. The compounds [Cu(bbp)(NCS)(SCN)]·MeOH (1) and [Cu(bbp)(SCN)Cl]·MeOH·H2O (2) have been studied by IR, UV–Vis spectroscopy and single crystal X-ray analysis. The electronic spectra of 1 and 2 were analyzed and bands were assigned through the DFT/TDDFT procedures. Simultaneous existence of N- and S-coordinated thiocyanate groups makes the complex 1 a rare example of [Cu(N–N–N)(SCN)2] structures. The energetically unfavorable S-binding of the thiocyanate group is stabilized by inter-molecular hydrogen bonds between the N atom of the apical SCN− and the N–H proton of L ligand of an adjacent molecule.