Two different isomers of tetrahedrally distorted square-planar Cu(II) triflate compounds with 2-guanidinobenzimidazole; synthesis, X-ray and spectroscopic characterisation

Abstract

In this study we report two isomers of Cu(2gb) 2(CF 3SO 3) 2 (in which 2gb=2-guanidinobenzimidazole), i.e. purple α-Cu(2gb) 2(CF 3SO 3) 2 ( 1) and green β-Cu(2gb) 2(CF 3SO 3) 2 ( 2) compounds. The Cu(II) atoms adopt a distorted tetrahedral geometry in both compounds. The difference between both isomers is the position of the triflate anions. In compound ( 2) one of the triflate anions is at a long semi-coordination distance, while in compound ( 1) the anions are at a much longer distance. That fact implies also that the hydrogen bonding system and the packing is different between the two compounds. The characterisation for both isomers has been performed by X-ray crystallography and infrared spectroscopy. A distortion towards tetrahedral is observed for both Cu(II) compounds with dihedral torsion angles at around 40° in both cases.