Synthesis, structure, spectroscopic properties, electrochemistry, and DFT correlative studies of N-[(2-pyridyl)methyliden]-6-coumarin complexes of Cu(I) and Ag(I)

6-Aminocoumarin reacts with pyridine-2-carboxaldehyde and has synthesized N-[(2-pyridyl)methyliden]-6-coumarin (L). The ligand, L, reacts with [Cu(MeCN)4]ClO4/AgNO3 to synthesize Cu(I) and Ag(I) complexes of formulae, [Cu(L)2]ClO4 and [Ag(L)2]NO3, respectively. While similar reaction in the presence of PPh3 has isolated [Cu(L)(PPh3)2]ClO4 and [Ag(L)(PPh3)2]NO3. All these compounds are characterized by FTIR, UV–Vis and 1H NMR spectroscopic data. In case of [Cu(L)(PPh3)2]ClO4 and [Ag(L)(PPh3)2]NO3, the structures have been confirmed by X-ray crystallography. The structure of the complexes are distorted tetrahedral in which L coordinates in a N,N′ bidentate fashion and other two coordination sites are occupied by PPh3. The ligand and the complexes are fluorescent and the fluorescence quantum yields of [Cu(L)(PPh3)2]ClO4 and [Ag(L)(PPh3)2]NO3 are higher than [Cu(L)2]ClO4 and [Ag(L)2]NO3. Cu(I) complexes show Cu(II)/Cu(I) quasireversible redox couple while Ag(I) complexes exhibit deposition of Ag(0) on the electrode surface during cyclic voltammetric experiments. gaussian 03 computations of representative complexes have been used to determine the composition and energy of molecular levels. An attempt has been made to explain solution spectra and redox properties of the complexes.

N-[(2-Pyridyl)methyliden]-6-coumarin (L) complexes of Cu(I) and Ag(I) are described. The structures are supported by X-ray crystallographic study. Ligand acts as bidentate N,N′ chelator. The complexes show emission activity. Electrochemistry shows Cu(II)/Cu(I) redox couple along with ligand reduction. DFT and TD-DFT calculations are used to interpret spectra and redox propertiesFigure optionsDownload as PowerPoint slideResearch highlights
► Coumarin is a photoactive biologically important phytochemical.
► It is functionalized by incorporating diimine function (-N=C-C=N-) and has synthesized N-[(2-pyridyl)methyliden]-6-coumarin (L).
► Copper(I) and silver(I) complexes of L are characterized by spectroscopic techniques and the single crystal structure shows distorted tetrahedral geometry.
► The compounds are fluorescent. The copper(I) complexes show Cu(II)/Cu(I) quasireversible couple while Ag(I) complexes deposit Ag(0) on the electrode surface during cyclic voltammetric experiment.
► DFT computation of optimized geometry has explained the electronic structure, spectra and redox properties.