Micro-environmental fine-tuning of electronic and kinetic properties of photochromic dyes

Abstract

Despite the recognition of the importance of Spiropyran (SP)–Merocyanine (MC) photochromic materials in molecular switching, the majority of studies have been reported in solution with relatively few in the solid-state as required in modern displays and other devices. In contrast, the present work bridges solution, condensed phase and solid-phase media and is to our knowledge the first micro-environmental study on electronic and kinetic effects for the SP–MC system. Expanding on our previous work we have investigated the photochromic properties of an SP molecule (1b) attached to a 100 μm commercially available polystyrene micro-particle (Wang Resin). The thermal MC → SP reversion kinetics (5a,b → 4a,b and 2a,b → 1a,b) which reflect the critical lifetime of the open MC form were measured. Reduction in kobs of thermal reversion, MC → SP, up to two orders of magnitude, and a blue-shift up to 58 nm was observed with the potential for tailoring or fine tuning. The use of polymeric micro-particles in controlling both electronic and kinetic properties of photochromic molecular switches has been highlighted.