Copper(II) complex with 6-(3,5-dimethyl-1H-pyrazol-1-yl)-2-(pyridin-2-yl)pyrimidin-4-amine: synthesis, crystal structure, and electronic spectroscopy

Abstract

A copper(II) complex with 6-(3,5-dimethyl-1H-pyrazol-1-yl)-2-(pyridin-2-yl)pyrimidin-4-amine (L), [CuLCl2], has been synthesized. This compound is formed irrespective of the Cu : L molar ratio (Cu : L = 1 : 1, 2 : 1, and 20 : 1) in the MeOH/H2O/DMF mixture as a single product. ESI-MS data demonstrate that the additional amount of CuCl2 above the Cu : L = 1 : 1 molar ratio, is effectively solvated, and high-nuclearity species are formed in trace amounts in the solution. The complex adopts a distorted square-pyramidal geometry with two chlorides and three nitrogen atoms from L. The electronic spectrum of the complex contains a broad band with a maximum at 12,820 cm−1 within the region characteristic for square-pyramidal chromophores CuA5 (A = Cl, N). Due to Cu ··· Cl contacts, the molecules of [CuLCl2] form the dinuclear [CuLCl2]2 unit. Surprisingly, the NH2-group participates in the formation of NH ··· Cl hydrogen bonds instead of the formation of (NH ··· N3(pyrimidine))2 synthon, which is common for N-heteroaromatic compounds containing the NH2-group in the α-position to aza-atom. These hydrogen bonds together with Cu ··· Cl contacts result in the formation of a 3-D-structure.