Mn(IV) and Co(III) complexes of tridentate -OH-rich ligands possessing O2N, O3N and O4N donor sets were synthesized, characterized and their structures were established by single crystal X-ray diffraction, where the binding core is O4N2. In the structurally characterized complexes, the coordination geometry about the metal ion was found to be distorted octahedral. © 2003 Elsevier Ltd. All rights reserved.