Synthesis, characterization, luminescence and catalytic properties of heterobimetallic quinoline based Cu(I)/Fe(II) hybrid complexes

A series of Cu(I)/Fe(II) hybrid complexes with the formula [Cu(Fc-CHNC₉H₆N)(PPh₃)₂]X (2–5) and [Cu(Fc-CHNC₉H₆N)(dppe)]X(6–9) [where Fc=Ferrocene, PPh₃ = triphenylphosphine, dppe = 1,2-bis(diphenylphosphino)ethane, and X = NO₃^-, ClO₄^-, BF₄^-, and PF₆^-] have been prepared and characterized on the basis of elemental analyses, IR, UV–visible, ¹H NMR,¹³P NMR and Mass spectral studies. Thermal stability of 2–5 and 6–9 has been investigated by using thermogravimetric analysis (TGA). Cyclic voltammetry of the all complexes revealed quasireversible redox behavior for the Cu(I)/Cu(II) and Fe(II)/Fe(III) pairs and it is sensitive to phosphine ligand. Red shifted emission in all complexes attributed to ligand-ligand charge transfer (LLCT), metal-ligand charge transfer (MLCT), or both and vary markedly with size of the counter anion and nature of phosphine ligand. All the complexes were tested for catalytic activity and it reveals that complexes with dppe ancillary ligand shows greater activity for the CC coupling of phenylacetylene with aryl iodides as compared to PPh₃ ligand. Additionally, the counter ions significantly affected the yield of the coupling product.