Photoswitchable Arylazopyrazole-Functionalized Ag₈ Nanoclusters with Light-Modulated Photoluminescence

Smart molecular photoswitches are an important member in the realm of artificial materials, which can exhibit distinct physicochemical properties under photoirradiation, yet light-driven silver nanocluster switches have been scarcely exploited due to their intrinsic photoinstability. Herein, two photostable isostructural photoresponsive Ag₈ nanoclusters (Ag8a and Ag8b) with a bicapped triangular prismatic Ag₈ core protected by the ternary ligands of arylazopyrazole, aryl-thiolate, and diphosphine have been synthesized and characterized comprehensively. The introduction of arylazopyrazole augments a fresh functionality to the silver nanocluster, realizing photoisomerization switched photoluminescence. The Ag₈ nanoclusters can be reversibly isomerized between trans and cis conformations with quite high efficiency under UV and visible light irradiation, respectively, which can occur in both solid and solution states and be conveniently monitored by time-dependent UV-Vis spectroscopy. More interestingly, the trans-cis isomerization process is accompanied by a significant bathochromic shift of the emission band from orange to red. This work not only presents a strategic guidance for synthesizing photoresponsive silver nanoclusters but also provides a new opportunity for developing photoswitchable fluorescent materials.