Synthesis, structure, redox properties and theoretical calculation of copper(I)-triphenylphosphine halide complexes of arylazopyridines, and their reaction with H2O2

Reaction of CuX (X = Cl, Br, I), PPh3 and 2-(arylazo)pyridine, R-H4C6NNC5H4N (aap, 1 where R = H (pap), p-Me (p-tap), m-Me (m-tap)) has synthesized [Cu((aap)(PPh3)X]. The structure has been established by spectroscopic (UV–Vis, 1H NMR) data and by single crystal X-ray diffraction of [Cu((pap)(PPh3)Br]. Addition of H2O2 to [Cu((aap)(PPh3)Cl] has afforded blue Cu(II) complexes, [Cu(aapO)(PPh3)Cl]. These complexes have been characterized by elemental analyses, IR, UV–Vis spectral and magnetic data. Upon addition of H2S saturated dil. H2SO4 solution to [Cu(aapO)(PPh3)Cl] free aapOH is separated and has been characterized by spectral data. Cyclic voltammogram of [Cu((aap)(PPh3)X] shows Cu(II)/Cu(I) response at 1.00–1.15 V and azo reduction at negative to SCE. DFT calculation of optimized structure of a representative complex has been used to determine the composition and energy of molecular levels and data have been used to explain the electronic spectral and redox properties.

[Cu((aap)(PPh3)X] (aap = 2-(arylazo)pyridine; X = Cl, Br, I) are characterized by spectral data and single crystal X-ray diffraction study in case of [Cu((pap)(PPh3)Br]. The complexes are oxidized by H2O2 to blue [Cu((aapO)(PPh3)Cl]; From which free ligand, aapOH are separated upon addition of H2S saturated methanol solution to [Cu(aapO)(PPh3)Cl]. Cyclic voltammogram of [Cu((aap)(PPh3)X] show Cu(II)/Cu(I) response at >1.00 V and azo reduction at negative to SCE. DFT calculation of optimized structure has been used to explain the spectral and redox properties.Figure optionsDownload as PowerPoint slide