On the Condensed Phase Ring-Closure of Vinylheptafulvalene and Ring-Opening of Gaseous Dihydroazulene

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-dihyd...

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Published in:	The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Vol. 117; no. 16; pp. 3340 - 3347
Main Authors:	Schalk, Oliver, Broman, Søren L, Petersen, Michael Å, Khakhulin, Dmitry V, Brogaard, Rasmus Y, Nielsen, Mogens Brøndsted, Boguslavskiy, Andrey E, Stolow, Albert, Sølling, Theis I
Format:	Journal Article
Language:	English
Published:	Washington, DC American Chemical Society 25-04-2013
Subjects:	Ab initio calculations Atomic and molecular physics Azulenes - chemistry Bonding Calculations and mathematical techniques in atomic and molecular physics (excluding electron correlation calculations) Condensing Cyclopentanes - chemistry Electronic structure of atoms, molecules and their ions: theory Exact sciences and technology Gas phases Gases Ground state Isomerization Kinetics Light Molecular Structure Origins Photoelectron Spectroscopy Physical chemistry Physics Potential energy Thermodynamics Photoelectron spectra Photoinduced effect Ab initio calculations Gas phase Ground states Isomerization
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Summary:	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.
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	1089-5639 1520-5215 1520-5215
DOI:	10.1021/jp400616c