Schiff base-type Cu(I) complexes containing naphthylpyridyl-methanimine ligands featuring higher light-absorption capability: Synthesis, structures, and photophysical properties

Abstract

Herein, the three novel copper (I) complexes bearing Schiff base ligands of the types [Cu(Methoxyphenyl-NaphthylPyridyl-Meth-Aniline)(POP)]PF6 (P1), [Cu(NaphthylPy-Methylene-Adam-Amine)(POP)]PF6 (P2), and [Cu(Dipp-NaphthylPyridyl-Meth-Aniline)(POP)]PF6 (P3) (Methoxyphenyl-NaphthylPyridyl-Meth-Aniline = 4-methoxyphenyl-N-((5-(naphthalen-1-yl)pyridin-2-yl)methylene)aniline, NaphylPy-Methylene-Adam-Amine = N-((5-(naphthalen-1-yl)pyridin-2-yl)methylene)adamantan-1-amine, Dipp-NaphylPyridyl-Meth-Aniline = 2,6-diisopropylphenyl-N-((5-(naphthalen-1-yl)pyridin-2-yl)methylene)aniline, POP = bis[2-diphenylphosphino]-phenyl)ether) have been prepared and investigated. The different groups such as methoxyphenyl, adamantyl and diisopropylphenyl were functionalized onto the azomethine unit of the Schiff base ligands to tune the photophysical behaviors of the resulting Schiff base Cu(I) complexes. All the complexes exhibit the lowest energy metal-to-ligand charge transfer (MLCT) characters in the visible region with higher molar extinction coefficients on the order of 104 M−1 cm−1, making them much attractive as photosensitizers in optoelectronic and light-harvesting applications. Blue-green emissions in the region of 479–513 nm with photoluminescence quantum yields (PLQY) of 0.8–1.2 % can be observed in CH2Cl2 solution. Additionally, the photophysical properties are also investigated theoretically using density functional theory (DFT) and time dependent DFT.