Synthesis, spectral and thermal studies of new Schiff base copper(II) complexes with their biological effect on Entomopathogenic nematodes

Abstract

New Schiff base ligands; (Z)‐1,5‐diphenyl‐2‐((thiophen‐2‐ylmethylene)amino)‐1H‐pyrrole‐3‐carbonitrile (L1); or (Z)‐2‐((2,4‐dihydroxybenzylidene)amino)‐1,5‐diphenyl‐1H‐pyrrole‐3‐carbonitrile (H2L2) and their Cu(II) complexes have been isolated and characterized using elemental analysis, spectral (FT‐IR, 1H NMR, UV/vis, EPR), molar conductivity and magnetic moment measurements, in addition to thermal techniques. FT‐IR spectra established that the Schiff base L1 coordinates as neutral bidentate or tridentate ligand. While the Schiff base H2L2 ligates as neutral or monobasic bidentate ligand. The EPR spectra indicated covalent nature of complexes [CuL1(OH)]Cl.2H2O (1), [CuL1(OH)(H2O)2]NO3.2H2O (2), [Cu(H2L2)Cl(H2O)3]Cl.H2O (5) and [Cu(HL2)NO3(H2O)3].H2O (6). The biological effect of Cu(II) ions, current ligands and complexes (1, 5) on the mortality and rate of reproduction of Entomopathogenic nematodes (Heterorhabditis bacteriophora and Steinernema carpocapsae) was studied. The results showed that, the obtained Schiff base ligands and their Cu(II) complexes make detoxification of the lethal effect of Cu(II) ions on the beneficial Entomopathogenic nematodes and complex (1) scored the highest reproduction potential.