Competition between cyclization and unusual Norrish type I and type II nitro-acyl migration pathways in the photouncaging of 1-acyl-7-nitroindoline revealed by computations

Abstract The 7-nitroindolinyl family of caging chromophores has received much attention in the past two decades. However, its uncaging mechanism is still not clearly understood. In this study, we performed state-of-the-art density functional theory calculations to unravel photo-uncaging entirety, and compared probabilities all plausible pathways. We found competition between a classical cyclization an acyl migration pathway, here explain electronic steric reasons behind such competition. possesses characteristics combined Norrish type I 1,6-nitro-acyl variation II mechanism, which reported for first time. also negligible energetic differences mechanisms 4-methoxy-5,7-dinitroindolinyl (MDNI) cages their mononitro analogues (MNI). traced experimentally observed improved quantum yields MDNI higher population reactants triplet surface. This fact supported by more favorable intersystem crossing due availability number excited states with correct symmetry than MNI. Our findings may pave way cage designs that possess efficient agonist release.