Session 3A: Inaugural Lectures by Associates/Fellow

Chairperson: S Sivasanker, Indian Institute of Technology, Chennai

Hetero-metallic complexes derived from N₂O₂ donor ligands: Molecular shapes, supramolecular structures, catalysis and magnetism View Presentation

The symmetrical and unsymmetrical N₂O₂ donor salen type di-Schiff base complexes of Cu(II) and Ni(II) can conveniently be used as ‘metalloligands’ as the oxygen atoms of the chelated Schiff base often coordinate to a second metal ion. Using the metalloligands, [CuL] or [NiL], several heterometallic complexes incorporating various metal ions along with some anionic coligands have been synthesised. The complexes are obtained in different shapes, which have been determined mostly by the coordination modes of the anionic coligands. Some fundamental solid state phenomena like ‘isomerism’ (linear-bent, coordination position and supramolecular isomerism) ‘polymorphism’, ‘cocrytallization’ are ob-served in such trinuclear complexes due to the flexibility in the coordination mode of, both, the metal and anionic co-ligands. Most heterometallic compounds satisfy non-zero spin ground state hence show ferrimagnetic exchange interactions. The coupling usually occurs through diphenoxido bridge between the metal centres. However, the anionic coligand can also take part in bridging to modulate the bridging angles and hence the coupling constant. Moreover, some of these compounds, consisting of Cu^II₂Dy^III, Cu₂Tb^III etc. are found to behave like Single Molecule Magnets, and the shapes of the molecule are found to have a considerable effect on the SMM behaviours. The catalytic oxidase activities, e.g., catechol-oxidase- and phenoxazinone-synthase- like activities of some of these heterometallic complexes are found to be very high presumably due to heterometallic cooperative effect.