# Hypercarbon‐Centered Gold(I)‐Copper(I) Clusters Exhibiting a Dissolution/Crystallization‐Induced Photoluminochromism

## TL;DR

This paper explores how carbon-centered gold-copper clusters change their light emission when dissolving or crystallizing, depending on the type of ligand used.

## Contribution

The study reveals a ligand-dependent dissolution/crystallization-induced photoluminochromism with over 100 nm emission shifts.

## Key findings

- Phosphine-protected clusters show a large bathochromic shift (>100 nm) in solution.
- NHC-protected clusters exhibit minimal PL change during dissolution/crystallization.
- Structure changes from octahedral to triangular prismatic in solution explain the emission shift.

## Abstract

Chemical molecules may show very different properties in the solid state and in solution, which is mainly caused by the difference in structure between different physical states. Well‐defined metal cluster molecules are ideal models for the investigation of the dynamic dissolution/crystallization process, as they usually exhibit photoluminescence (PL) that is sensitive to reversible changes in coordination geometry and multi‐electron structure. Here we report the dissolution/crystallization‐induced photoluminochromism (PLC) of carbon‐centered AuI
6CuI
2 clusters bearing pyridylphosphine or pyridyl N‐heterocyclic carbene (NHC) ligands. These clusters, with an octahedral structure doubly capped with copper(I), exhibit greenish‐yellow emission in the solid state. Remarkably, the PL of the NHC‐protected clusters in solution changes only slightly, whereas the phosphine‐protected clusters exhibit red PL accompanied by a large bathochromic shift (>100 nm), a reversible process upon dissolution equilibration. X‐ray absorption spectroscopy and theoretical calculations suggest that the octahedral CAuI
6 structure in the crystal is twisted into a triangular prismatic structure in solution. This remarkable ligand effect on the dissolution/crystallization‐induced PLC would provide advanced design guidance for stimuli‐responsive chromic materials.

A novel photoluminochromism (PLC, > 100 nm shifts) of carbon‐centered gold cluster bearing pyridylphosphine ligands is reported. Upon dissolution/crystallization, the greenish‐yellow emissive solids and red emissive solution may reversibly convert into each other, and such processes are prohibited when utilizing pyridyl N‐heterocyclic carbene (NHC) as ligands. The origin of such chromism is a structure twist in the metal core of the cluster.