We report the synthesis and solution- and solid-state characterization of gold(I) rings with short 1,9-transannular Au...Au interactions. The 9- and 16-membered gold(I) rings were prepared by reacting 9,9-dimethyl-4,5-bis(diphenylphosphino)-xanthene and (Me2S)AuCl in the presence of AgNO3 in the molar ratio of 1:0.5:1 and 1:1:1, respectively. X-ray crystallographic measurements in conjunction with solution X-ray diffraction and NMR methods have been used to determine the structure of gold(I) rings, and we also gained insight into the dynamics. The nine-membered gold(I) ring is chiral, and the crystal contains only one of the two enantiomers, either right- or left-handed. To the best of our knowledge this represents the first example of crystallization-induced spontaneous resolution of a binuclear gold(I) cycle. The 16-membered ring with 1,9-transannular Au...Au interaction is in a figure-eight conformation.

The role of noncovalent interactions is reviewed in the context of the stimuli‐responsive behaviour of gold(I) and gold–heterometal complexes. These noncovalent interactions are often highly sensitive to physical (thermal, optical, electrical, mechanical, etc.) or chemical (solvents, guests, etc.) stimuli, which trigger alterations in molecular and crystal structures that lead to dynamic changes in the macroscopic properties of gold compounds. In this microreview, we have summarized some representative examples of gold(I) complexes that exhibit intriguing stimuli‐responsive properties such as thermochromic, mechanochromic, vapochromic and solvatochromic luminescence, as well as vapochromism and gas sorption. Stimuli‐responsive functional materials with specific properties have potential uses in various applications including chemical sensors, memory, data storage, security inks and separation technologies.

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A series of [Au2 (nixantphos)2](X)2 (nixantphos=4,6-bis(diphenylphosphino)-phenoxazine; X=NO3, 1; CF3 COO, 2; CF3 SO3, 3; [Au(CN)2], 4; and BF4, 5) complexes that exhibit intriguing anion-switchable and stimuli-responsive luminescent photophysical properties have been synthesized and characterized. Depending on their anions, these complexes display yellow (3), orange (4 and 5), and red (1 and 2) emission colors. They exhibit reversible thermo-, mechano-, and vapochromic luminescence changes readily perceivable by the naked eye. Single-crystal X-ray studies show that the [Au2 (nixantphos)2](2+) cations with short intramolecular Au⋅⋅⋅Au interactions are involved as donors in an infinite N-H⋅⋅⋅X (X=O and N) hydrogen-bonded chain formation with CF3 COO(-) (2 C) and aurophilically linked [Au(CN)2](-) counterions (4 C). Both crystals show thermochromic luminescence; their room temperature red (2 C) and orange (4 C) emission turns into yellow upon cooling to 77 K. They also exhibit reversible mechanochromic luminescence by changing their emission color from red to dark (2 C), and orange to red (4 C). Compounds 1-5 also display reversible mechanochromic luminescence, altering their emission colors between orange (1) or red (2) to dark, as well as between yellow (3) or orange (4 and 5) to red. Detailed photophysical investigations and correlation with solid-state structural data established the significant role of NH⋅⋅⋅X interactions in the stimuli-responsive luminescent behavior.