Tetra-Fe(III) and deca-Mn(III) metallacrowns built from bis-salicylhydrazide ligands: synthesis, structures and magnetic properties

Four new coordination metallacrowns were obtained via self-assembly of Fe(III) and Mn(III) ions with N-1',N-5'-bis(5-X-2-hydroxybenzoyl)glutarohydrazide (X = Cl, H(6)pentaCShz; X = Br, H(6-)pentaBShz) in DMF at room temperature. These metallacrowns consist of four or ten [M-N-N] repeated units with M = Fe(III) for 1 and 2, and M = Mn(III) for 3 and 4. In the systems containing different metal salts, it has been demonstrated that the 12-membered rings in 1 and 2 can be augmented to 30-membered cycles in 3 and 4 due to their metal coordination nature. Quasi-tetrahedra are formed in the tetra-nuclear ferric compounds and two fused distorted tetrahedra are accommodated in the deca-nuclear manganic ones. In other words, the morphologies of the metallacrowns in 1-4 are controlled by varying the metal and flexibility of the glutaryl group in H(6)pentaXShz. Magnetic studies of all the four compounds indicate antiferromagnetic coupling interactions between adjacent metal centers.