Aggregation Enhances Luminescence and Photosensitization Properties of a Hexaiodo-BODIPY

Intramolecular rotations are known to interfere with the excited-state processes resulting in luminescence quenching. Efforts aimed at restricting intramolecular rotations have led to the development of highly luminescent systems. Here we report the luminescence properties of a BODIPY molecule (I6) containing six iodo-substituents. The luminescence of I6 was highly quenched in the solution state whereas the conversion of this molecule into its nanoaggregates enhanced the emission intensity. Detailed photophysical studies and molecular simulations were employed to study the underlying mechanism which showed that the electron-withdrawing nature of iodine atoms and the peculiar structure of I6 contributed towards the anomalous luminescence behaviour. Further, the luminescence and photosensitization properties of I6 were exploited for cell imaging and photodynamic therapy. Thus, our simple but intelligent molecular design yielded a multi-faceted molecule having excellent photophysical properties for potential photobiological applications.