Water Dissociation of a Dinuclear Bis(3,5-dimethylpyrazolyl)methane Copper(II) Complex: X-ray Diffraction Structure, Magnetic Properties, and Characteristic Absorption of the (CuN2Cl2)2 Core

A complex of formula [{CuCl{H2C(3,5-Me(2)pz)}}(2)(mu-Cl)(2)] (1) is obtained and its structure is determined by single-crystal X-ray diffraction crystallography, revealing dinuclear character supporting a (CuN2Cl2)(2) core. Compound 1 undergoes water dissociation that generates a change in the coordination sphere of the metals, yielding a mononuclear Cu-II complex of the formula [CuCl{H2C(3,5-Me(2)pz)(2)}(2)]Cl3H(2)O (2), as supported by LeBail analysis and visible absorption spectroscopy. Interestingly, the optical features of 1 unravel characteristic patterns in the absorption spectrum, attributed solely to the formation of the (CuN2Cl2)(2) core. The study of the magnetic properties of 1 reveals weak antiferromagnetic exchange coupling between the two Cu-II ions that is transmitted through the double-chloro bridge, which is supported by broken-symmetry DFT calculations.