Breaking Bonds by Light: The Absorbance–Fragmentation Paradox

Abstract

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 (σ₂) 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 σ₂ = 86 GM and uncaging cross‐section δ_u = 10.2 GM at 735 nm.