Three new heteroleptic copper(I) complexes of the form [Cu(N,N)(XantPhos)]PF₆ were synthesized and characterized, where N,N refers to phenyl-substituted imidazo[4,5-f][1,10]phenanthroline. All complexes were obtained as yellow powders in yields ranging 82–95% and were fully characterized by NMR spectroscopy, FT-IR, and mass spectrometry. The complexes were also redox-optically characterized. Their absorption profiles display a lower-energy metal-to-ligand charge-transfer (MLCT) band at approximately 412 nm. In solution, weak dual emission is observed, combining ligand-centered and MLCT contributions, with oxygen-dependent quenching supporting the presence of triplet character in the latter. Temperature- and solvent-dependent studies reveal thermally coupled emissive states, in which a relaxed ³MLCT state dominates at low temperatures. In the solid state, intense orange-to-red emission arises from restricted molecular motion and stabilized ³MLCT states, with C3 showing the highest efficiency. Additionally, aggregation-induced emission (AIE) is observed in solvent mixtures. These results suggest that remote substitution can influence the excited-state dynamics and aggregation-driven emission in Cu(I) complexes.

In this study, we report the synthesis and characterization of three Cu(I) complexes bearing functionalized dipyridylamine ligands and DPEphos. Structural analysis confirms a distorted tetrahedral coordination environment around the metal center. Photophysical studies in DMSO show similar absorption profiles (λ_abs ≈ 341–343 nm) with ligand-centered and MLCT transitions, while emission spans the visible region (λ_emi = 410–483 nm) and is strongly influenced by ligand substitution, with the CF₃ derivative displaying a marked red shift. Emission is insensitive to oxygen and exhibits short lifetimes (τ ≈ 14.9–15.3 ns), suggesting short-lived ¹MLCT excited states. Biological evaluation in A375 melanoma cells reveals that all complexes exhibit low-micromolar cytotoxicity under dark conditions (IC₅₀ = 3.33–4.92 μM). Notably, only the CF₃-substituted complex shows a significant light-induced enhancement of activity upon irradiation at 390 nm (IC₅₀ = 1.18 μM), indicating photoactivation.