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.

Keywords:

• Copper(II)
• N-ligands
• Synthesis
• Supramolecular chemistry

Acknowledgments

We are grateful to I.V. Yushina for recording of the diffuse reflectance spectrum of the complex and to V.G. Vasiliev for recording of ESI-MS of the complex. M.B.B. is grateful to S.G. Kozlova and K.A. Vinogradova for their help with quantum chemical calculations. The work was partially supported by Russian Foundation for Basic Research (Grant No.12–03–00392–a).