Copper(II) complexes with (2-hydroxybenzyl-2-pyridylmethyl)amine-Hbpa: syntheses, characterization and crystal structures of the ligand and [Cu(II)(Hbpa)(2)](ClO4)(2)center dot 2H(2)O

Copper(II) complexes were synthesized and characterized by means of element al analysis, IR and visible spectroscopies, EPR and electrochemistry, as we ll as X-ray structure crystallography. The group consists of discrete monon uclear units with the general formula [Cu(II)(Hbpa)(2)](A)(2). nH(2)O, wher e Hbpa = (2-hydroxybenzyl-2-pyridylmethyl)amine and A = ClO4- n = 2 (1), CH 3COO-, n = 3 (2), NO3-, n = 2 (3) and SO42-, n = 3 (4). The structures of t he ligand Hbpa and complex 1 have been determined by X-ray crystallography. Complexes 1-4 have had their UV-Vis spectra measured in both MeCN and DMF. It was observed that the compounds interact with basic solvents, such that molecules coordinate to the metal in axial positions in which phenol oxyge n atoms are coordinated in the protonated forms. The epsilon values were al l less than 1000 M-1 cm(-1). EPR measurements on powdered samples of 1-3 ga ve g(parallel to)/A(parallel to) values between 105 and 135 cm(-1), typical for square planar coordination environments. Complex 4 . 3H(2)O exhibits a behaviour typical for tetrahedral coordination. The electrochemical behavi our for complexes 1 and 2 was studied showing irreversible redox waves for both compounds. (C) 1999 Elsevier Science S.A. All rights reserved.