Two new end-on cyanato copper(II) complexes; synthesis, characterization, solvatochromism, magnetic investigation and quantum study

Abstract

The present paper deals with magnetic interactions, solvatochromism and DFT calculations of two new end-on cyanato-bridged dinuclear copper(II) complexes with the formula [L(OCN)Cu(μN,N-OCN)]2, 1 and 2, where L1 = N,N-dimethyl,-N′-benzyl-ethylenediamine (1) and L2 = N,N-diethyl,-N′-benzyl-ethylenediamine (2). Both complexes were characterized on the basis of physicochemical and spectroscopic methods. X-ray crystallography of complex 2 showed a dinuclear nature with terminal and bridging cyanate groups. Each copper atom achieves a distorted square-pyramidal environment that is built up by five nitrogen atoms, with two nitrogen atoms coming from two N-bonded cyanato ligands that link two copper ions in an end-on fashion, one nitrogen atom from another cyanato ligand that acts as an N-bonded terminal ligand and the final two nitrogen atoms are from a chelating diamine ligand. The interaction between the two metal ions was investigated by magnetic measurements from 2 to 300 K. The variable temperature magnetic susceptibility data showed a weak ferromagnetic interaction with J values of 1.8 cm−1 for 1 and 7.7 cm−1 for 2. DFT computational results buttressed the experimental observations. The positive solvatochromic behaviors of the compounds were investigated in some organic solvents. The spectral shifts of these solutes were correlated with Kamlet and Taft parameters (α, β and π∗) using linear solvation energy relationships (LSEC). The multi-parametric analysis indicates that both the polarity/polarizability parameters (π∗) and the hydrogen bond donating ability (β) of the solvents play an important role in the absorption maxima of the compounds.