The development of enediyne-based photonucleases, which is underway in our group, requires robust and efficient methods for the photogeneration of a triple bond. We have recently demonstrated that UV/Vis photolysis of cyclopropenones (1) results in efficient (φ=0.3-0.8) loss of CO and quantitative formation of alkyne.

DFT calculations predict that decarbonylation of cyclopropenones is a stepwise process with intermediate formation of a zwitter-ion 2. Simultaneous elongation of both C-CO bonds, on the other hand, leads to a maximum on the PES.

The photodecarbonylation of 2,3-di-naphthalen-1-yl-cyclopropenone and 2,3-bis-(2-methoxy-naphthalen-1-yl)-cyclopropenone was studied using time-resolved UV and IR spectroscopy. We have found that formation of carbon monoxide is complete within 30 ns, while formation (τ ~ 10 ps) and decay (τ ~ 150 ps) of an intermediate 2 has been observed on a faster time scale.