Structure, fluorescence, redox properties and theoretical interpretation of heteroleptic copper(I) and silver(I) complexes of N-[(2-pyridyl)methyliden]-6-coumarin and triphenylphosphine

• Cu(I) and Ag(I) complexes of N-[(2-pyridyl)methyliden]-6-coumarin (L).
• Distorted tetrahedral structure.
• Highest emissivity of [Cu(SCN)(L)(PPh3)].
• Coulometric oxidation of Cu(I) complexes to Cu(II) complexes.
• DFT computation of the optimized structures.

[MX(L)(PPh3)] (L = N-[(2-pyridyl)methyliden]-6-coumarin; M = Cu(I), Ag(I); X = Cl, Br, I, N3, SCN) are characterized by spectroscopic data. The X-ray structure of [CuCl(L)(PPh3)] shows CuN2PCl distorted tetrahedral coordination (L acts N,N chelator). The complexes show emission and the emission efficiency is dependent on nature of M and X; Cu(I) complexes (d10) are more emissive than Ag(I) complexes which may be due to heavy atom effect of silver. [Cu(SCN)(L)(PPh3)] shows highest emission intensity in the series. The cyclic voltammogram of [CuX(L)(PPh3)] shows Cu(II)/Cu(I) quasireversible redox couple while [AgX(L)(PPh3)] exhibits deposition of Ag(0) on the electrode surface together with irreversible ligand reduction. Coulometric oxidation of [CuX(L)(PPh3)] has synthesised copper(II) derivatives. Theoretical calculations are applied in modelling of complexes studied and UV–Vis spectra simulation.

N-[(2-pyridyl)methyliden]-6-coumarin (L) is used to synthesize [MX(L)(PPh3)] (M = Cu, Ag; X = Cl, Br, I, N3, SCN). The X-ray structure of [CuCl(L)(PPh3)] shows distorted tetrahedral geometry along with hydrogen bonded, π⋯π bonded 2D structure. [CuX(L)(PPh3)] are more emissive than L and its heavier metal analogue, [AgX(L)(PPh3)]. [Cu(SCN)(L)(PPh3)] shows highest quantum yield. The cyclic voltammogram of [CuX(L)(PPh3)] shows Cu(II)/Cu(I) quasireversible redox couple. DFT and TD-DFT computation support spectral and redox properties of the complexes.Figure optionsDownload as PowerPoint slide