Combined experimental and computational study of cis-trans isomerism in N,N-disubstituted-N’-acylthiourea ligands in bis-chelated copper(II) complexes

• Computational Chemistry useful, but energy differences too small for differentiation. • Careful ligand design can allow for control of stereochemistry. • Appears the cis geometry is more thermodynamically controlled. • A hypothetical model put forward and is open for further exploration. The synthesis, molecular structure determination and a Density Functional Theory (DFT) investigation of the structure of several new complexes of copper(II) with nine N,N -disubstituted -N’ -acylthiourea (HL) ligands is reported. Characterisation of these complexes was achieved using a combination of FT-IR, elemental analysis, electron paramagnetic resonance spectroscopy, powder X-ray diffraction and single crystal X-ray diffraction analysis. The XRD studies revealed the presence of a distorted square planar geometry for all the complexes synthesised. It was found that fine tuning the Acyl and NRR ’ substituent of the complexes can afford some level of control in terms of the cis or trans outcome for the compounds. DFT studies were performed to investigate the cis/trans isomerism. The calculations found a difference in energy between the two isomers smaller than 1.2 kcal mol −1 , suggesting that the two geometries are equally possible for all copper(II) complexes.