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

Adekunle Oluwafunmilayo F. (Ladoke Akintola University of Technology, Department of Pure and Applied Chemistry, P.M.B., Ogbomoso, Nigeria + Howard University, Department of Chemistry, Washington DC, USA)
Butcher Ray (Ladoke Akintola University of Technology, Department of Pure and Applied Chemistry, P.M.B., Ogbomoso, Nigeria + Howard University, Department of Chemistry, Washington DC, USA)
Bakare Oladapo (Ladoke Akintola University of Technology, Department of Pure and Applied Chemistry, P.M.B., Ogbomoso, Nigeria + Howard University, Department of Chemistry, Washington DC, USA)
Odunola Olusegun A. (Ladoke Akintola University of Technology, Department of Pure and Applied Chemistry, P.M.B., Ogbomoso, Nigeria + Hallmark University, Department of Chemistry, Ijebu Itele, Nigeria)

[Cu(phen)2(CH3COO)](ClO4).2H2O (1) and [Cu(bipy)2(CH3COO)]-(ClO4).H2O (2) {phen = 1,10-phenanthroline, bipy = 2,2’-bipyridine}were synthesized and characterized. The complexes were characterized by employying elemental analyses, infrared and UV-Visible spectroscopy, room temperature magnetic measurements and the crystal structures elucidated using X-ray diffraction experiment. 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) Å for (1) and 2.179 (1) for (2)] and Cu-N [2.631(2) Å for (1) and 2.714(1) Å for (2)] bonds. This distortion if further shown by the O-Cu-N bond angles [147.71(8) o for (1) and 153.40(5) o for (2)]. The elemental analyses further support the structural details unveiled by the single crystal X-ray diffraction analysis. The infrared spectra shows the acetate vibrational frequencies at 1587 cm-1,1428 cm-1, 1314 cm-1 for (1) and 1571 cm-1, 1441 cm-1, 1319c m-1 for (2) and the perchlo-rate bands at 1059 cm-1, 720 cm-1 (1) and 1080 cm-1,768 cm-1 (2). The broad d-d bands for the copper ion at 14,514 cm-1(1) and 14,535 cm-1(2) support the adoption of square pyramid geometries. The magnetic moments for the two complexes are 1.83 B.M for (1) and 1.72 B.M for (2). The peak to peak values of the two complexes show that the electrode reactions are quasi-reversibile with ΔEp = 0.023V (1) and 0.025V for (2). In both structures, there are π-π intermolecular interactions in addition to hydrogen bonding between the units.

Keywords: X-ray structure determination, copper polypyridyl complexes, π-π interactions, CuN4O chromophore, quasi-reversible