title: On the condensed phase ring-closure of vinylheptafulvalene and ring-opening of gaseous dihydroazulene.
abstract: Dihydroazulenes are interesting because of their photoswitching behavior. While the ring-opening to vinylheptafulvalene (VHF) is light induced, the back reaction is known to proceed thermally. In the present paper, we show the first gas phase study of the ring-opening reaction of 2-phenyl-1,8a-dihydroazulene-1,1-dicarbonitrile (Ph-DHA) by means of time-resolved photoelectron spectroscopy which permits us to follow the ring-opening process. Moreover, we investigated s-trans-Ph-VHF in a series of transient absorption experiments, supported by ab initio computations, to understand the origin of the absence of light-induced ring-closure. The transient absorption results show a biexponential decay governed by a hitherto unknown state. This state is accessed within 1-2 ps and return to the ground state is probably driven through a cis-trans isomerization about the exocyclic C1═C2 double bond. The rapid decrease in potential energy disfavors internal rotation to s-cis-Ph-VHF, the structure that would precede the ring-closure reaction.
authors.affiliation: Stockholm University, AlbaNova University Center, Roslagstullsbacken 21, SE-10961 Stockholm, Sweden.
authors.forename: Oliver
authors.initials: O
authors.lastname: Schalk
authors.forename: Søren L
authors.initials: SL
authors.lastname: Broman
authors.forename: Michael Å
authors.initials: MÅ
authors.lastname: Petersen
authors.forename: Dmitry V
authors.initials: DV
authors.lastname: Khakhulin
authors.forename: Rasmus Y
authors.initials: RY
authors.lastname: Brogaard
authors.forename: Mogens Brøndsted
authors.initials: MB
authors.lastname: Nielsen
authors.forename: Andrey E
authors.initials: AE
authors.lastname: Boguslavskiy
authors.forename: Albert
authors.initials: A
authors.lastname: Stolow
authors.forename: Theis I
authors.initials: TI
authors.lastname: Sølling
mesh_terms: D052176:Azulenes / Q000737:chemistry*; D003517:Cyclopentanes / Q000737:chemistry*; D005740:Gases; D007700:Kinetics; D008027:Light; D015394:Molecular Structure; D056951:Photoelectron Spectroscopy; D013816:Thermodynamics
chemical_list: D052176:Azulenes; D003517:Cyclopentanes; D005740:Gases; C507545:dihydroazulene