Aspects of the chemistry of copper(II) complexes having different nuclearity

Abstract

Synopsis of the thesis entitled “Aspects of the chemistry of copper(II) complexes having different nuclearity” to be submitted by Mrs. K. Geetha under the supervision of Prof. A. R. Chakravarty of the Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore – 560 012 for the Ph.D. degree in the Faculty of Science. The chemistry of mono-, di- and polynuclear copper(II) complexes is of importance towards understanding the structural, electronic and magnetic properties of the active sites of several copper-containing metalloproteins. This thesis deals with the syntheses of monomeric, dimeric and high nuclearity copper(II) complexes and the study of their magneto-structural properties. Asymmetrically di- and tribridged dicopper(II) complexes having a [Cu?(OR)(O?CR)?]?? (m = 1, 2; n = 2, 1) core viz. [Cu?(OH/OMe)(O?CPh)?(tmen)?] (PF?) (1), Cu?(OH)(O?CPh)?(tmen)? (2), Cu?(OH)(O?CC?H?-p- Me)(tmen)?? (3) and Cu?(OH)(O?CC?H?-p-OMe)(tmen)?? (4) have been synthesized. X-ray crystallographic studies (Chapter II) of these complexes were made and a magneto-structural correlation (Chapter III) has been obtained. A tribridged dicopper(II) complex Cu?(O?CC?H?-p-Me)?(tmen)? (5) has been obtained from a similar reaction at 0 °C using copper(II)-p-methylbenzoate as a precursor complex. Complex 5, however, magnetochemically behaved like a dibridged complex. The X-ray structure and other physico-chemical properties of complex 5 are presented in detail in Chapter IV. The reactions of tetraarylcarboxylatodicopper(II) complexes having electron- withdrawing substituents at the para position of the benzoic acid with tmen resulted in the formation of monomers of composition [Cu(O?CC?H?-p-X)?(tmen)] (6–8). The X-ray crystal structures and properties of these complexes were studied in detail (Chapter V). The interesting feature of these molecules is the observation of chemically significant C–H...O interactions. In order to prepare dicopper(II) complexes having alkoxo–carboxylato bridges with an additional binding site on the carboxylate ligand, a reaction of copper(II) perchlorate with a pentadentate ligand H?L, derived from the condensation of salicylaldehyde and 1,3-diamino-propan-2-ol (2:1 ratio), in presence of isonicotinic acid has been found to produce a novel polymeric copper(II) complex [Cu?(L)(O?CC?H?N)]? (9). The X-ray structure and its magnetic properties have been investigated in detail (Chapter VI). The reaction of copper(II) perchlorate with a different pentadentate Schiff-base ligand (H?L?), obtained from the condensation of 1,3-diamino-propan-2-ol and acetylacetone, in the presence of KOH has been found to form a novel octanuclear copper(II) complex [Cu?(L?)?(OH)?]·3H?O·C?H?? (10) which has a hydrophobic exterior and a hydrophilic metallamacrobicyclic core showing selective hydrogen-bonding interactions. The complex exhibits novel non- covalent interactions. The X-ray structure and magnetic properties of this complex are given in Chapter VII. The details of the X-ray crystallographic and magnetic data are presented in Appendices I–VI of the thesis.