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

Abstract

[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 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) Å for 1 and 2.179(1) Å for 2) and Cu–N (2.631(2) Å for 1 and 2.714(1) Å for 2) bonds. This distortion was further shown by the O–Cu–N bond angles (147.71(8)° for 1 and 153.40(5)° 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 mB for 1 and 1.72 mB for 2. The peak-to-peak values of the two complexes show that the electrode reactions are quasi-reversible with ΔEp of 0.023 V for 1 and 0.025 V for 2. In both structures, there are π–π intermolecular interactions in addition to hydrogen bonding between the units.