One-Photon Responsive Photoremovable Protecting Groups (PRPGs) for Release of Bioactive Molecules

During the last 18 years, my group has developed several PRPGs that can uncage diverse functionalities like carboxylic acids, alcohols, amines, etc. Perylene, Pyrene, Benzo[a]acridinyl, Acetyl Carbazole, Bimane, and Carboline are notable PRPGs developed by our research group. The developed PRPGs offer uncaging in a remotely controlled manner, introducing spatiotemporal precision using light. Interestingly, some of the PRPGs have unique properties like tunable fluorescence, fast and clean photorelease, self-monitoring photorelease, and biocompatibility. In continuation, one of the often-limited limitations of a new PRPG is its absorptivity in the lower wavelengths of light, resulting in an inferior tissue penetration depth. Hence, we significantly put effort into the chemical modification, engaging the donor-acceptor concept or increasing π-conjugation to reach a higher wavelength of activation. In particular, we have developed quinoxaline-based PRPG absorbing in the UV-Vis region, and further modification enables its absorptivity in the green to NIR region. Similar to that, phenothiazine-based protecting groups showed their photocleavage under UV-A to blue light, whereas the successful implementation of conjugated iminium analog pushed their operational wavelength in the NIR region.