Synthesis, characterisation and X-ray crystal structure of copper(II) complexes with unsym-metrical tetradentate Shiff base ligand: first evidence of Cu(II) catalysed rearrangement of unsymmetrical to symmetrical complex

The mononuclear copper(II) complexes, [CuL1](ClO4) and [CuL2](ClO4) with unsymmetrical quadridentate Schiff base ligands have been prepared and characterised. The second complex undergoes Cu(II)/H+ catalysed rearrangement to [CuL3](ClO4)2 where L3 is a symmetrical tetradentate Schiff base involving 1,3-propanediamine and pyridine-2-carboxaldehyde. Structures of all the three compounds have been verified by single crystal X-ray analysis. The geometry around Cu(II) is square-planar in the first and second complexes whereas that in the three is distorted octahedral.