Crystal structure, magnetism and spectroscopy of two strongly antiferromagnetically coupled dinuclear Cu(II) paddlewheel-like compounds with 4-azabenzimidazole as a ligand

Two dinuclear compounds, [Cu2(azab)4Cl2]Cl2(CH3OH)3 (1) and [Cu2(azab)4Br2]Br2(H2O)1/2 (2) (in which azab = 4-azabenzimidazole), have been synthesized and characterized by infrared spectroscopy and EPR. Also the X-ray structures of both compounds and the magnetic susceptibility have been investigated, and the dinuclear structural details are presented.The geometries of both structures are similar. Each copper(II) ion has a square pyramidal geometry with the basal plane formed by four nitrogen atoms of four bischelating azab molecules in a paddlewheel-like fashion. The apical position is occupied by a chloride or bromide anion, respectively.The EPR spectra show a resolved triplet, S = 1, spectrum for both compounds (including the ΔMs = ±2 transition splitted into seven lines at 77 K) with a zero-field splitting (D) of 0.124 cm−1. The magnetic susceptibility measurements (from 5 to 300 K) agree with a strong overall antiferromagnetic interaction with a large singlet–triplet splitting of J = −329 and −349 cm−1, for compounds 1 and 2, respectively.

Two paddlewheel-like dinuclear compounds, [Cu2(azab)4Cl2]Cl2(CH3OH)3 (1) and [Cu2(azab)4Br2]Br2(H2O)1/2 (2) (in which azab = 4-azabenzimidazole), have been synthesized. Characterization is done by X-ray crystallography, infrared spectroscopy and EPR. Also the magnetic susceptibility of both compounds are investigated and obtained a strong antiferromagnetic interaction between the Cu(II) ions.Figure optionsDownload as PowerPoint slide