Photoinduced single-crystal-to-single-crystal phase transition and photosalient effect of a gold(<scp>i</scp>) isocyanide complex with shortening of intermolecular aurophilic bonds

Abstract

We report the first photoinduced single-crystal-to-single-crystal (SCSC) phase transition of a gold complex that involves the shortening of intermolecular aurophilic bonds. This is also the first solid state photochromism of a gold complex. Upon UV irradiation, the blue-emitting crystals of the gold(i) isocyanide complex <b>1</b> (<b>1B</b>) transform into the weakly yellow-emitting polymorph <b>1Y</b>. X-ray diffraction analyses reveal that this phase transition proceeds in an SCSC manner. After phase transition from <b>1B</b> to <b>1Y</b>, the intermolecular Au···Au separation decreases from 3.5041(14) to 3.2955(6) Å, resulting in a red-shifted emission. The photoinduced shortening of the aurophilic bond in the excited state initiates the change in the crystal structure from <b>1B</b> to <b>1Y</b>. Moreover, the crystal <b>1B</b> showed a photosalient effect: the <b>1B</b> crystals jump upon irradiation with strong UV light owing to the phase transition into <b>1Y</b>. The aurophilic bond formation in the crystal generates the mechanical movement of the crystal.