Ultrafast Photoelimination of Nitrogen from Upper Excited States of Diazoalkanes and the Fate of Carbenes Formed in the Reaction.

The photochemical reactivity of diphenyldiazomethane and phenyl 1- and 2-adamantyl diazomethanes and , respectively, was investigated by transient absorption spectroscopy (TA). Photoelimination of N upon UV excitation takes place in the anti-Kasha ultrafast photochemical reaction from the upper excited singlet states to deliver singlet carbenes, which were, in the case of and , detected by fs-TA. The reactivity of the carbenes differs with respect to the substituent at the carbene center.

Photogeneration of quinone methide from adamantylphenol in an ultrafast non-adiabatic dehydration reaction.

The ultrafast photochemical reaction of quinone methide (QM) formation from adamantylphenol was monitored in real time using femtosecond transient absorption spectroscopy and fluorescence upconversion in solution at room temperature. Experiments were complemented by theoretical studies simulating the reaction pathway and elucidating its mechanism. Excitation with sub-20 fs UV pulses and broadband probing revealed ultrafast formation of the long-lived QM intermediate directly in the ground state, occurring with a time constant of around 100 fs.