EPR Spectra of Copper(II) Complexes with Biguanide Derivatives

Department of Chemistry, Regional Engineering College, Kurukshetra-132 119 

Manuscript received 7 August 1987, revised 14 October 1987, accepted 73 November 2987

Copper(II) complexes of quadridentate ligands, viz., ethylenedibiguanide, trimetby­lenedibiguanide, m-phenylenedibiguanide, piperazinedibiguanide, and bidentate ligand phenylbiguanide have been studied by epr spectroscopy in polycrystalline form and in the corresponding Ni^II complex matrix. Epr spectra of the complexes hi the corres­ponding Ni^II complex matrix exhibit nine nitrogen superhyperfiue lines on the high field 3/2 ↔ 3/2 copper hyperfine splitting components indicating the presence of four equivalent nitrogen atoms around the Cu^II ion. The evaluation of the covalency para­meters from the epr data indicates that the unpaired electron of Cu^II spends about 31 —36% of its time in the nitrogen donor sites of the ligands. The epr spectra of the complexes suggest the presence of CuN₄ coordination sphere in the complexes. A comparison of the bonding parameters of the Cu^ll dibiguanide complexes with those of the Curl complexes of biguanide and phenylbiguanide indicates that the bridging group in quadridentate dibiguanides has negligible effect on the epr spectra and bonding para­meters. A comparison of the bonding parameters of the present complexes with those of the Cu^II complexes of tetrapenylporphine and phthalocyanine indicates that biguanides and dibiguanides rank among strong field ligands.