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

The compartmental Schiff base ligands N,N′-ethylenebis(3- hydroxysalicylidene) (H₄L) and N,N′-propylenebis(3- hydroxysalicylidene) (H₄L′) have been employed in the synthesis of a cyclic tetranuclear Cu(ii) complex [Cu₄(L′) ₂(MeOH)₃(H₂O)]·[Cu₄(L′) ₂(MeOH)₃] (1), a novel octanuclear Cu(ii) complex [Cu ₈(L-L)₂(H₂O)₄(μ₂- H₂O)]·3DMF·3H₂O (2) and a hetero-octanuclear Cu(ii)-Fe(iii) complex [Cu₄Fe₄(L)₄(H ₂O)₃(μ₃-O)₂] ·3DMF·3H₂O (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 H₄L ligands. The bicyclic complex (2) is comprised of two cyclic Cu₄ units that are similar to that of complex 1. In the Cu₄ 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°.