Synthesi,s and characterization of some Mn(II) and Mn(III) complexes of N,N′-o-phenylenebis(salicylideneimine)(LH2) and N,N′-o-phenylenebis(5-bromosalicylideneimine)(L′H2).: Crystal structures of [Mn(L)(H2O)(ClO4)], [Mn(L)(NCS)] and an infinite linear chain of [Mn(L)(OAc)]

A series of manganese(H) [Mn(L)] and manganese(Ill) [Mn(L)(X)] (X = ClO4, OAc, NCS, N-3, Cl, Br and I) complexes have been synthesized from Schiff base ligands N,N '-o-phenylenebis(salicylideneimine)(LH2) and N,N '-o-phenylenebis(5-bromosalicylideneimine)(L ' H-2) obtained by condensation of salicylaldehyde or 5-Br salicylaldehyde with o-phenylene-diamine. The complexes have been characterized by the combination of IR, UV-Vis spectroscopy, magnetic measurements and electrochemical studies. Three manganese(III) complexes 3[Mn(L)(ClO4)(H2O)], 5 [Mn(L)(OAc)] and 13 [Mn(L)(NCS)] have been characterized by X-ray crystallography. The X-ray structures show that the manganese(III) is hexa-coordinated in 3, it is penta-coordinated in 13, while in 5 there is an infinite chain where the MnL moieties are connected by acetate ions acting as bridging bidentate ligand. The cyclic voltammograms of all the manganese(111) complexes exhibit two reversible/quasi-reversible/irreversible responses assignable to Mn(III)/ Mn(11) and Mn(IV)/Mn(III) couples. It was observed that the ligand L ' H-2 containing the 5-bromosal moiety always stabilizes the lower oxidation states compared to the corresponding unsubstituted LH2. Cyclic voltammograms of the manganese(II) complexes (I and 2) exhibit a quasi -reversible Mn(III)/Mn(II) couple at E-1/2 -0.08 V for I and 0.054 V for 2. (c) 2005 Elsevier B.V. All rights reserved.