Synthesis, EPR and biological activities of bis(1- n-butylamidino- O-alkylurea)copper(II)chloride complexes: EPR evidence for binuclear complexes in frozen DMF solution

Abstract

Copper(II) complexes of the type [Cu(1-Bu n AAUH) 2]Cl 2, where 1-Bu n AAUH = 1- n-butylamidino- O-alkylurea and alkyl = methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl have been synthesized and characterized by elemental analyses, magnetic moments, conductivity measurements, electronic absorption, IR and EPR spectroscopy. The EPR spectra of these complexes in frozen solutions of DMF showed a signal at g ca. 2. In addition to this, a signal at half the resonance field, having well resolved seven-line hyperfine structure, was observed. The EPR signals at g ca. 2 and at the half-field have been interpreted as arising from Δ M s = ±1 and Δ M s = ±2 transitions, respectively, occurring as a result of the formation of a binuclear complex. The trend in g value ( g ∥ > g ⊥ > 2.00) suggests that the unpaired electron on copper has d x 2 - y 2 character and the complex has a square planar structure. Based on the EPR and electronic spectral data, the bonding parameters of these complexes in MeOH have been calculated. The metal-ligand bonding parameters evaluated showed strong in plane σ and in plane π bonding. The bis(1- n-butylamidino- O-alkylurea)copper(II)chloride complexes show growth inhibitory activity against pathogenic fungi, viz., Ceratocystis paradoxa, Aspergillus niger, Trichoderma koningii and pathogenic bacteria, viz., Bacillus sps(1), Bacillus sps(3).