Synthesis and crystal structure of a novel mixed ligand copper complex

Isothiosemicarbazone as one of the thiosemicarbazones derivatives has shown biological properties especially anticancer propreties. In these compouds an alkyl group binds to the sulfur atom, and the coordination accomplishes via thioamide nitrogen instead of thioamide sulfur [1]. On the other hand, interaction of nucleobases with metal ions has been a subject of several studies because of their chemical and biological importance. Among them, adenine as an N-rich nucleobase has proved to be a rather versatile metal-binding biomolecule [2]. This molecule shows wide range of binding possibilities because it exhibits at least five nitrogen donor sites, and a great variety of complexes with different metal binding patterns have been reported [2]. In this study, we synthesized a new mixed ligand copper(II) complex of isothiosemicarbazone with adenine as an auxiliary ligand and examined its structure using X-ray crystallography.Perspective view of the centrosymmetric Cu dimer complex is presented in figure 1. Each Cu atom has a distorted square pyramidal coordination geometry in which a tridentate ONN isothiosemicarbazone ligand in addition to an adenine molecule fill the equatorial sites. The adenine molecule coordinates Cu via N4 in the form of neutral monodentate ligand. An oxygen atom (O1) from the other isothiosemicarbazone molecule places in the axial site and constitutes an attractive Cu1∙∙∙O1i (2.674 Å) (symmetry code: (i) -x,1-y,1-z) bond. Displacement of O1 is the main factor of distortion of the complex structure so that it lies 0.188 Å away from the Cu1C9N1N2N3 mean plane.