Metastable induced electron spectroscopy

The IR spectra after irradiation were assigned to the original l,2 -dimer, produced 2,2 -dimer and lophyl radical. Moreover, the spectra also indicate that this photochemical process is reversible. The existence of the 2,2 -dimer has been assumed from the spectroscopy but the structure analysis has not been successful, because the 2,2 -dimer is easily transformed to the l,2 -dimer. The 2,2 -dimer with 4n-4n electron system is less stable than the l,2 -dimer with 4n.-6% system. The theoretical calculation indicated that the l,2 -dimer is stabler by 5.9 kcal moH than the 2,2 -dimer. The in situ X-ray crystallography shown here is a very powerful method to capture the light-induced metastable intermediates such as a 2,2 -dimer. 

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