阴离子配位抑制偶氮苯型分子镊子热弛豫行为研究

The azobenzene-based molecular tweezers can regulate the uptake and release of substrate upon light irradiation making it extensively studied in the fields of molecular recognition, catalysis, and transmembrane transport. The investigation of thermal relaxation behaviors contributes to understanding the photochemical and photophysical properties of photoswitch molecules and provides design principles of new azobenzene molecules. Strong coordination of cationic or neutral substrates with the cis isomer can suppress the thermal relaxation rate of azobenzene units. However, due to the increased charge density in the azobenzene double bond region, anion coordination typically accelerates the thermal relaxation rate. In this study, azobenzene-based bis-bis(urea) ligands were designed. With enhanced multiple hydrogen bonding interactions, the thermal relaxation rate of azobenzene was successfully suppressed upon anion coordination. Compared with the free ligand, the thermal relaxation rate of chloride-coordinated single helix was decreased by 20%, and the thermal relaxation rate of sulfate-coordinated double helicate was decreased by 50%.