Synthesis, characterization and DFT studies of luminescent copper(I) complexes containing pyridine-imidazole ligands with tunable π-conjugation system via variation of polyaromatic groups.

[Display omitted] • Cu(I) complexes with polyaromatic substituents are synthesized and characterized. • The photophysical properties of the corresponding complexes is studied. • Extended π system has important influence on the light absorption abilities. • DFT/TDDFT methods were employed to understand the photophysical properties. The three Cu(I) complexes [Cu(POP)(N^N)]PF 6 , N^N = 2-(1 H -imidazol-2-yl)-5-(naphthalen-2-ylethynyl)pyridine (P1), 2-(1 H -imidazol-2-yl)-5-(phenanthren-9-ylethynyl)pyridine (P2), 2-(5-(naphthalen-2-ylethynyl)pyridin-2-yl)-1 H -phenanthro[9,10- d ]imidazole (P3), were prepared and characterized. The photophysical properties of these Cu(I) complexes is tuned by extending π- system of the N^N ligand through the addition of polyaromatic groups such as naphthalene and phenanthrene into the pyridine ring part of the diimine ligands via an acetylide linker or phenanthrene-fused imidazole ring. The resulting complexes exhibit higher absorption ability in the visible region. The emissions are in the range of 582–601 nm with quantum yields of 2.30–7.70% and the excited lifetimes of 77.4–115.8 μs for all complexes at room temperature. The photophysical properties were further explained by DFT and TDDFT methods. [ABSTRACT FROM AUTHOR]