Metal-Regulated Excited-State Intramolecular Proton Transfer and Excimer Pathways to Achieve Full Spectrum Luminescence.

Abstract

We have developed a novel metal-organic photoluminescence system that exhibits a coupled behavior of excited-state intramolecular proton transfer (ESIPT) and excimer luminescence. The emitter can achieve full-spectrum luminescence from blue, green, yellow to red, including white light through enol-keto-excimer tristate modulation. Transient absorption analysis combined with theoretical calculation indicates that the first step of Zn2+ metal coordination promotes molecular stacking, transforming the original single-molecule ESIPT emission into ESIPT and excimer dual emission. The second step of Cu2+ or Ni2+ metal coordination further triggers the ESIPT and excimer fusion mechanism to bear significant solvent dependence character, for which the two competing processes are dominated by the degree of molecular aggregation in different solvents. The results provide new insights into how ESIPT and excimer processes can be coupled and regulated within a single platform and establish a metal-coordination strategy for constructing ESIPT-excimer-coupled systems toward multilevel luminescent materials and applications.