Synthesis, spectra, structure, redox properties and DFT computation of copper(I)–triphenylphosphine–pyridyl Schiff bases

The reaction of 2-(2′-pyridylmethyleneamino)pyridine (L1)/3-(2′-pyridylmethyleneamino)pyridine (L2)/4-(2′-pyridylmethyleneamino)pyridine (L3) with CuX (X = Cl, Br, I) and triphenylphosphine (PPh3) affords complexes of composition [Cu(L)(PPh3)X]. These are characterized by microanalytical data and spectroscopic studies (IR, UV–Vis, 1H NMR). The single crystal X-ray structure determines the distorted tetrahedral geometry about Cu(I) in case of [Cu(L2)(PPh3)I]. Cyclic voltammogram shows Cu(II)/Cu(I) couple at 0.5–0.6 V, in addition [Cu(L)(PPh3)I] shows iodide oxidation peak at 0.3 V. Redox couple negative to SCE may be assigned to the reduction of chelated diimine function. Electronic structure, spectra, emission properties and redox activities are explained by DFT calculations of optimized geometry of [Cu(L2)(PPh3)X] and have been used to determine the composition and energy of the molecular levels.