Photocages are light-sensitive protecting groups with a covalent linkage to a molecule of interest. Generally, the active site of the substrate is involved in the covalent bond formation and this, in turn, diminishes the activity of the caged molecule significantly. Upon excitation with light of a particular wavelength, the substrate is released and the original biological activity of the molecule is restored. These spatial and temporal control of the photocages over the reactivity of the substrate attributes to their widespread recognition as attractive chemical tools for investigations as well as cargo-release of molecules like drugs, fluorescent dyes, phototherapeutic agents, signaling agents, nucleotides, ions and other bioactive molecules. The most desirable wavelength range for the photocages is from 600-1000 nm, often called the biological window, as they can penetrate deep inside the living tissue with minimum amount of phototoxicity. Our group was successful in synthesizing efficient first generation and second generation BODIPY photocages that absorb in this region. We have determined the quantum yield of photorelease of the second generation green and red BODIPYs with different leaving groups like carboxylic acids, amines, alcohols, halides and phosphates, in order to investigate the role of the leaving groups in the photorelease and to compare the difference in release rates with or without linkers. Our current goal and ongoing work are to develop BODIPY photocages with an anti-aromatic ground state which will push the absorption furthermore in the far-red or near IR region (above 850 nm), in comparison to the available photocages, which will make them an outstanding choice for biological applications.

Exploration of BODIPY photocages: Scope of functional group caging and achieving red-shifted absorptions

ACS Spring 2022

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