Design and characterization of Cu(II) complexes from 2-benzoylpyridine benzhydrazone: Crystallographic evidence for coordination versatility

The syntheses and characterization of six copper(II) complexes of 2-benzoylpyridine benzhydrazone in the form of [Cu(BPB)2], [Cu(BPB)Cl]·H2O, [Cu(BPB)Br], [Cu2(BPB)2](ClO4)2·4H2O, [Cu(BPB)N3]·H2O, and [Cu(BPB)NCS]·H2O·CH3OH are reported. The analytical methods used for the characterization of complexes include partial elemental analyses, IR, electronic and EPR spectra, conductivity measurements, magnetic susceptibility measurements and single crystal X-ray diffraction. From the crystal structure, it is clear that the hydrazone adopts the E conformation about the azo bond to attach to the metal through the Npy–Nazo–O chelating system. In the EPR spectra of complexes in DMF at 77 K four hyperfine quartets in the parallel region could be resolved and a half field signal is observed at 1500 G for complex [Cu2(BPB)2](ClO4)2·4H2O in polycrystalline state at 298 K which gives evidence for its binuclear nature indicating a weak interaction between the two Cu(II) ions.