Syntheses, structure, and magnetic properties of heteronuclear Cu(<scp>ii</scp>)₄Fe(<scp>iii</scp>)₄cluster and Cu(<scp>ii</scp>)₈bimetallacycles

Abstract

The compartmental Schiff base ligands N,N'-ethylenebis(3-hydroxysalicylidene) (H(4)L) and N,N'-propylenebis(3-hydroxysalicylidene) (H(4)L') have been employed in the synthesis of a cyclic tetranuclear Cu(II) complex [Cu(4)(L')(2)(MeOH)(3)(H(2)O)]·[Cu(4)(L')(2)(MeOH)(3)] (1), a novel octanuclear Cu(II) complex [Cu(8)(L-L)(2)(H(2)O)(4)(μ(2)-H(2)O)]·3DMF·3H(2)O (2) and a hetero-octanuclear Cu(II)-Fe(III) complex [Cu(4)Fe(4)(L)(4)(H(2)O)(3)(μ(3)-O)(2)]·3DMF·3H(2)O (3). During the formation of the Cu(8) complex (2), a new bis-Schiff base ligand (L-L)(8-) forms via the ortho-para C-C coupling of two H(4)L ligands. The bicyclic complex (2) is comprised of two cyclic Cu(4) units that are similar to that of complex 1. In the Cu(4) unit, the alternate Cu(II) ions are singly bridged by phenoxo groups. The three complexes display overall antiferromagnetic coupling, and the Cu(II)-Cu(II) magnetic coupling constant falls in the range -117.2 to -473.6 cm(-1) for complexes 1 and 2 corresponding to the bridging Cu-O(phenoxide)-Cu bond angles of 124.3-131.0°.