Metal ion complexes with N-acylpeptides: Part IV-Preparation and characterization of copper(II) and zinc(II) complexes with N-formyl-<img src='http://www.niscair.res.in/jinfo/small.gif' border=0>- phenylalanylglycine and their adducts

Abstract

Complexes of the type ML₂-2H₂O [M= copper(II) or zinc(II) and L = N-formyl-- phenylalanylglycine] have been prepared. Adducts of the type ML₂-Bn.xH₂O (n = 2 for B = pyridine, 2-picoline, 3-picoline, 4-picoline, triphenylphosphine oxide; n = 1 for B= 2,2'-bipyridyl and 1,10-phenanthroline where x varies between zero and four) have been obtained by the reaction of ML₂-Bn.xH₂O with monodentate or bidentate ligands. Six-coordinate structures are proposed for all the complexes on the basis of analytical data and various physicochemical techniques. The ESR spectra of Cu(formphegly)₂.2H₂Oand Cu(formphegly)₂(TPPO)₂ indicate the presence of both dimeric copper (<em>S</em> = 1) and monomeric copper (<em>S</em> = 1/2) species. A signal due to <img src="http://www.niscair.res.in/jinfo/delta.gif" alt="" border="0" /><em>M</em>_s <em>= </em>± 2 transition is also observed. The <em>g </em>values obtained from the triplet state spectra have been used in the best-fitting of the susceptibility data for the calculation of the concentration of the monomer component (5%) in Cu(formphegly)₂(TPPO)₂ complex. The magnetic susceptibility of Cu(formphegly)₂ (TPPO)₂ has been measured in the temperature range 167-294 K. The copper-copper separation in the dimeric component is 3.943 A. In all the complexes, carboxylate group acts in a bidentate manner as shown by infrared spectra. Presence of both <em>cis </em>and <em>trans </em>isomers in ZnL₂.2H₂O is indicated by ¹³C NMR spectral data.