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.