Charge-Transfer Engineering Controls Excited-State Dynamics and Supramolecular Assembly in Luminescent Au(I) Complexes

Abstract

Coupling excited-state control with supramolecular self-assembly within a single molecular design remains a central challenge in luminescent materials chemistry. Here, we explore charge-transfer (CT) engineering as a strategy to address both features in a family of luminescent Au(I) bisphosphine complexes. Homoleptic derivatives bearing pyrene, phenanthrene, or triphenylene chromophores were compared with a heteroleptic pyrene/phenanthrene complex designed to promote interchromophoric electronic communication. The homoleptic complexes display predominantly room-temperature fluorescence, with increasing phosphorescence contributions associated with progressive metal perturbation of the excited states. In the heteroleptic complex, the combination of electronically differentiated chromophores enables access to a T2-mediated pathway that promotes room-temperature pyrene phosphorescence, as supported by solvent-dependent photophysical measurements and theoretical calculations. Addition of [Au(CN)2]− enhances fluorescence in all cases, with a 6-fold increase for the heteroleptic complex, and promotes its organization into extended luminescent wires driven by a combination of C–H···N≡C hydrogen bonding and π···π stacking interactions. These results show how chromophore differentiation within an Au(I) coordination scaffold can couple excited-state modulation with supramolecular organization, providing a design strategy for responsive luminescent assemblies.