Long-lived room temperature phosphorescence in aqueous micellar systems: application in cyclobutane synthesis

The micelle-induced excimer formation of simple chalcone is investigated. An extraordinarily long-lived NIR-emission displaying an average lifetime of 19.22 µs was recorded. The emission was induced by the unique micro-environment provided by the micelles and could not be observed simply by increasing the concentration in organic solvent. Using visible light overlapping with the recorded excitation spectrum, an intermolecular [2+2] photocycloaddition could be promoted, illustrating the synthetic potential of the concept. The incorporation of chalcone into the micelles displayed no apparent change in size or shape of the micelles as illustrated by TEM-images and diffusion NMR studies. In addition to providing a unique and essential environment for the present study, aqueous micelles represent an alternative to organic solvents for sustainable synthesis.