Breaking Bonds by Light: The Absorbance-Fragmentation Paradox.

Multi-branched probes based on 2-hydroxymethylene 8-dimethylaminoquinoline (8-DMAQ) and triphenylamine (TPA) have been synthesized and compared under UV and femtosecond near-infrared two-photon (2P) activation conditions. While octupolar (3) and quadrupolar (2) DMAQ derivatives showed superior ε and 2P absorption cross-section (σ) values relative to the dipolar (1) probe, the fragmentation efficiency exhibited an inverse correlation with the enhanced absorption. Compound 1 emerged as the most effective probe reported to date for the release of organic substrates under both UV and 2P activation conditions at wavelengths accessible to commercially available lasers, achieving a quantum yield (Q) of 12% with σ = 86 GM and uncaging cross-section δ = 10.2 GM at 735 nm.