Au···I coinage bonds: Boosting photoluminescence efficiency and solid-state molecular motion

Coinage bonds, a type of noncovalent interaction, occur between group 11 elements (Au, Ag, and Cu) with electron donor groups. Despite theoretical validation, empirical evidence remains limited. In this study, an aggregation-induced emission (AIE)-active Au(I) complex, ITCPAu, which exhibits Au···I coinage bonds, was revealed based on the single-crystal X-ray diffraction and theoretical calculations. Further examination of the luminescence properties of the ITCPAu revealed multiswitchable behavior, including mechanochromism and thermochromism. Nearly pure white-light emission was achieved with Commission Internationale de L'Eclairage (CIE) 1931 chromaticity coordinates of (0.30, 0.31) by grinding the green-emissive ITCPAu monomer crystals. Moreover, visualization and manipulation of solid-state molecular motion (SSMM) in the yellow-emissive ITCPAu dimer crystals, driven by the robust Au···I coinage bonds, were revealed through a combination of crystal engineering and luminescent properties. Furthermore, to support the robust Au···I coinage bonds, a versatile carrier for small solvent molecules in crystal lattices was developed for uptake and release. Our findings provide experimental and theoretical evidence for Au···I coinage bonds, highlighting their ability to boost photoluminescence quantum yield (PLQY) and trigger SSMM, emphasizing their potential in developing smart materials with stimuli-responsive properties.