# Heavy-Atom Effect Modulated Photoluminescence Properties of Trinuclear Copper(I) Clusters with Haloarylacetylene Ligands

## TL;DR

This paper explores how heavy atoms in ligands affect the light-emitting properties of copper(I) clusters, showing significant changes in color and brightness.

## Contribution

The study introduces a systematic investigation of the heavy-atom effect on photoluminescence in trinuclear copper(I) clusters with substituted arylacetylene ligands.

## Key findings

- The emission peak of Cu3-I reached 564 nm, a 73 nm red shift compared to Cu3-F.
- Cu3-Br showed a 3.3-fold increase in quantum yield and a 3.7-fold increase in lifetime compared to Cu3-F.

## Abstract

Copper(I) clusters have attracted significant interest due to their ultrasmall size, excellent photostability, large Stokes shift, and long emission lifetime. However, research on their structure–property relationship remains limited. In this study, we synthesized and comprehensively characterized a series of trinuclear copper(I) clusters, [Cu3(dppm)3(C≡CC6H4X)2]PF6 [Cu3-X, X = F, Cl, Br, and I, dppm = bis(diphenylphosphino)methane], in order to investigate the effect of ligands containing heavy atoms on photoluminescence. All clusters have the same triangular metal core and similar distribution of ligands, with the only difference being the substituent on the phenyl ring of the arylacetylene ligand. Owing to the heavy-atom effect, a notable Stokes shift was observed in the emission spectra of the clusters. Specifically, the emission peak of Cu3-I reached 564 nm, representing a 73 nm red shift compared to that of Cu3-F. Furthermore, Cu3-Br showed an absolute photoluminescence quantum yield of 15.24% and a lifetime of 114.56 μs, corresponding to 3.3-fold and 3.7-fold increases over the values for Cu3-F. This study provides novel insights into the heavy-atom effect of surface ligands on the luminescence of copper(I) clusters and offers a robust platform for probing their structure–property relationships.