Fine-tuning the lifetimes and energy storage capacities of meta-stable vinylheptafulvenes via substitution at the vinyl position

Using a dicyano-substituted dihydroazulene (DHA) as precursor, we can access a large selection of DHAs where one cyano group has been transformed into another functionality. Upon irradiation these DHAs are readily converted into the meta-stable vinylheptafulvenes (VHFs), whose half-lives are found to span from milliseconds to days. Thus, the nature of substituent groups at the vinyl position of VHF has a strong, although not simple to predict, influence on its ability to undergo a ring-closure reaction to form a DHA.