Synthesis, spectroscopic characterization, x‐ray crystal structures, thermal behavior and antimicrobial activity of copper(II) complexes with the novel (3,5‐dimethyl‐1H‐pyrazol‐1‐yl)(morpholin‐4‐yl)methanethione

Abstract

The new (3,5‐dimethyl‐1H‐pyrazol‐1‐yl)(morpholin‐4‐yl) methanethione ligand (L) and its copper(II) chelates Cu(L)Br2 (1), Cu(L)Cl2 (2) and [Cu(L)2OH(H2O)]ClO4·1.5H2O (3) have been prepared. The coordination behavior of the ligand and the properties of the chelate compounds have been investigated by several physico‐chemical techniques. The structures of (L), (1), and (2) have been characterized by x‐ray single crystal diffraction. The ligand (L) crystalizes in the monoclinic P21/n space group, a = 11.2632(4), b = 7.9959(2), c = 13.4337(5) Å, α = 90, β = 106.3080(14), γ = 90°. The copper(II) complexes (1) and (2) show a distorted square‐planar geometries, with the ligand behaves as a bidentates NS chelating agent, coordinating to the copper(II) ions through the N atom of the pyrazolyl ring and the thione S atom, the third and fourth coordination sites are occupied by two halogen (Br− or Cl−) ions. The ESR spectra of the prepared complexes are consistent with d(x2‐y2)1 ground state with axial symmetry. The thermal analysis data of the Cu(II) complexes (1 and 2) indicated that they have similar thermal degradation pathways. The complexes displayed antimicrobial activity against various pathogenic bacteria and fungi higher than that of the free organic ligand. The reaction of Cu(L)Cl2 (2) with pyridine (py) in ethanol at room temperature does not form mixed‐ligand complex, but leads to complete substitution of the ligand (L). The product of the substitution reaction was characterized based on elemental analyses and FT‐IR measurements.