Scientists Tune Light-Powered Chemical Reactions With Molecular Design Tricks
Researchers have discovered how to control the speed of light-triggered chemical reactions by strategically adding bulky molecules to a compound, accelerating reactions by over 20-fold. The technique enables precise control over photoclick chemistry—reactions that snap molecules together under visible light—opening pathways for secure data encryption, drug synthesis, and advanced manufacturing processes.
Originaltitel: Steric Engineering of Phenanthrenequinone for Ultrafast and Tunable Visible Light-Induced Photoclick Reaction
Light-induced 9,10-phenanthrenequinone-electron-rich alkene (PQ-ERA) photocycloadditions are an attractive new type of photoclick reaction featuring fast conversions. However, the tunability of the reaction has hardly been investigated up to now. To this end, we explored steric engineering at the PQ ortho-phenyl position as a powerful, unprecedented means to drastically modulate kinetics. Introducing steric groups (e.g., 2,6-dimethyl in PQ-o2CH3) enforced large dihedral angles (69.5°) as a result of which the 1nπ* state became the lowest electronically excited singlet state S1 instead of the 1ππ* state, while retaining T1 as 3ππ*, the triplet lifetime was boosted and an ultrafast direct [4 + 2] photoclick reaction was enabled. Critically, steric groups accelerated rates by >21-fold (k2 up to 11,300 M–1 s–1), spanning 2 orders of magnitude. Leveraging this novel steric–kinetic relationship, we demonstrated a “burn-after-reading” encryption concept via spatially controlled photoclick and rapid erasure by uniform isoconversion. This demonstration of steric control over PQ-ERA photoclick efficiency provides a foundation for designing orthogonal ultrafast conjugation systems.