Rapid Luminescent Enhancement Triggered by One-shot Needlestick-stimulus Using a Liquescent Gold(I) Salt.

Luminescence from a gold(I) complex with an N-heterocycliccarbene-based ligand, 1+ ⋅NTf2 - , increased rapidly upon the application of one-shot needlestick-stimulus. The weakly orange-emitting solid-state of 1+ ⋅NTf2 - was prepared by cooling its melted liquid to 90 °C. Upon applying a weak pinpoint stimulus with a needle, this weakly orange-emitting solid state transformed into an intensively violet-blue-emitting state on a timescale of seconds. The emission after applying the stimulus could be visualized upon UV excitation even under ambient room light. This sequential phase transition from a stable solid to a liquid and then to a metastable solid could occur repeatedly without any measurable degradation of the complex. Various shapes could be prepared by casting the liquid-state complex into molds of different designs. This rapid response is thought to be triggered by the flexible intermolecular interactions in the kinetically generated aggregates formed upon cooling the liquid state, and by the strong Au-Au interactions in the thermodynamically stable crystals after applying the needlestick-stimulus.