Mixed ligand copper(I) complexes with alkynyl functionalized iminopyridine and substituted ethynylpyridine ligands: Synthesis, photophysical properties and DFT studies

A series of mixed ligand copper(I) complexes of the formula [Cu(L1–3)(NC5H4C[tbnd]CH) (PPh3)]PF6 (1a-c), [Cu(L1–3)(NC5H4C[tbnd]CC6H4OCH3)(PPh3)]PF6 (2a-c) and [Cu(L1–3) (NC5H4 C[tbnd]CC6H4NO2)(PPh3)]PF6 (3a-c) have been synthesized by the reaction of [Cu(CH3CN)3 (PPh3)]PF6 with N-(2-pyridylmethylene)-4-(trimethylsilylethynyl)aniline (L1), N-(2-pyridylmethylene)-4-(ethynyl)aniline (L2) and N-(2-pyridylmethylene)-4-(phenylethynyl)aniline (L3) in presence of NC5H4C[tbnd]HNC5H4C[tbnd]CC6H4OCH3 and NC5H4C[tbnd]C C6H4NO2. All the complexes have been characterized on the basis of their elemental analyses, IR, 1H NMR, 31P NMR, and TGA-DTA studies. Electrochemical data demonstrate quasireversible redox behavior for all copper(I) complexes. Photophysical properties of all copper(I) complexes indicate that increase in π-conjugation and donor/acceptor substituents on coordinated ligands show a marked effect on the absorption and emission properties of the complexes. DFT computations were performed to gain insight into the effect of the donor/acceptor moiety of coordinated ligands on the HOMO-LUMO gap of the copper(I) complexes.