Synthesis, characterization, electrochemical studies and X-ray structures of mixed-ligand polypyridyl copper(II) complexes with the acetate

[Cu(phen)(2)(CH3COO)](ClO4)center dot 2H(2)O (1) and [Cu(bipy)(2)(CH3COO)](ClO4)center dot H2O (2) (phen = 1,10-phenanthroline, bipy = = 2,2'-bipyridine) were synthesized and characterized. The complexes were characterized by employing elemental analyses, infrared and UV-Vis spectroscopy, room temperature magnetic measurements and the crystal structures were elucidated using X-ray diffraction experiments. The redox properties of the complexes were also investigated. Both structures have a square pyramidal CuN4O chromophore, which exhibit significant distortions due to long Cu-O (2.217(3) for angstrom 1 and 2.179(1) for angstrom 2) and Cu-N (2.631(2) for angstrom 1 and 2.714(1) for angstrom 2) bonds. This distortion was further shown by the O-Cu-N bond angles (147.71(8)degrees for 1 and 153.40(5)degrees for 2). Elemental analyses further supported the structural details unveiled by the single crystal X-ray diffraction analysis. The infrared spectra show the acetate vibrational frequencies at 1587, 1428 and 1314 cm(-1) for 1, 1571, 1441 and 1319 cm(-1) for 2, and the perchlorate bands at 1059 and 720 cm(-1) for 1 and 1080 and 768 cm(-1) for 2. The broad d-d bands for the copper ion at 14.514 cm(-1) for 1 and 14535 cm(-1) for 2 support the adoption of square pyramid geometries. The magnetic moments for the two complexes were 1.83 mu(B) for 1 and 1.72 mu(B) for 2. The peak-to-peak values of the two complexes show that the electrode reactions are quasi-reversible with Delta E-p of 0.023 V for 1 and 0.025 V for 2. In both structures, there are pi-pi intermolecular interactions in addition to hydrogen bonding between the units.