Assembly-dependent thermochromic and photochromic luminescence in pentiptycene-based homoleptic gold(I) alkynyl clusters [(AuCCR)n]

Abstract

We report two stimuli-responsive luminescent assemblies based on homoleptic alkynyl gold(I) clusters, [(AuCCR)_n], where R is a pentiptycene unit and n = 4 or 6. The green-emissive form (1Gs) adopts a vortex-like arrangement and exhibits photochromic luminescence, shifting from green to yellow to orange. In contrast, the yellow-emissive form (1Ys) adopts a less rigid structure, likely a radial arrangement, and displays thermochromic luminescence, transitioning from yellow to orange to red. These divergent behaviors arise from structural differences in η²-Au bonding, which modulate supramolecular geometry, pentiptycene-pentiptycene packing, and the strength of Au⋯Au interactions, thereby governing excited state aurophilicity. This work demonstrates the first luminochromic [(AuCCR)_n] system and introduces a design strategy that leverages pentiptycene scaffolds to regulate excited-state aurophilicity for photo- and thermoresponsive luminescence.