The Crystal Structure and Electronic Properties of the Bis(1,3-dimethyl-5-diazophenyl-6-amino uracilato) Copper(II) Complex, Dimethyl Sulfoxide Solvate - A New Pseudotetrahedral CuN4 Complex.

Abstract The crystal structure of the title complex has been determined by X-ray diffraction technique. The crystals are monoclinic, space group P 2 1 / n , with a = 12.878(2), b = 14.791(1), c = 17.268(2) A, β = 109.79(1)°, Z = 4, R = 0.057 for 2514 reflections. There are two ligands of 1,3-dimethyl-5-diazophenyl- 6-amino uracilato anions in bidentate coordination to a copper(II) ion per asymmetric unit. The ligands are in cis -arrangement to each other. The copper environment is pseudotetrahedral, with a dihedral angle φ of 39.7° between the two CuN 4 ligand planes. This geometry seems to result from steric interaction between the ligands. The coordination of each molecule of the ligand takes place through the nitrogen atom of the deprotonated 6-amino group and a nitrogen of the azo group. The structure is stabilised by extensive stacking interactions between the phenyl rings as well as the pyrimidine rings. A pair of hydrogen-bonded interactions between the solvent molecule and the two ligands further stabilise the structure. The magnetic moment, ESR and electronic reflectance spectrum are in accordance with the observed molecular structure. A linear correlation between the highest energy d—d transition and the dihedral angle for several pseudotetrahedral N 4 complexes has been proposed.