Three‐Coordinated Heteroleptic Cu(I) Complexes with Bulky Phosphine Ligands: Influence of Substituents on Photophysical Properties

The design and synthesis of cost‐effective and environmentally friendly luminescent materials have great implications and challenges. In this study, bulky phosphine ligands (Sphos and Xphos) are utilized to synthesize a series of three‐coordinated Cu(I) complexes with different N^N ligands derived from 1,10‐phenanthroline. By employing rigid N^N donor ligands featuring different electron‐donating or withdrawing substituents, the emission from 585 to 698 nm with a microseconds lifetime in the solid state can be systematically modulated. While complexes 1 – 3 with 1,10‐phenanthroline and neocuproine exhibit emission around 590 nm, dicnq (featuring electron‐withdrawing groups) coordinated complexes 4 and 5 exhibit significantly redshifted emissions to ≈700 nm. The experimental and theoretical studies suggest the occurrence of thermally activated delayed fluorescence with microseconds lifetime and a small ΔE ST . This investigation highlights the pivotal role of ligand design in regulating the photophysical characteristics of Cu(I) complexes.