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Spatial confinement alters the ultrafast photoisomerization dynamics of azobenzenes.
Otolski, Christopher J; Raj, A Mohan; Ramamurthy, Vaidhyanathan; Elles, Christopher G.
Afiliação
  • Otolski CJ; Department of Chemistry, University of Kansas Lawrence Kansas USA elles@ku.edu.
  • Raj AM; Department of Chemistry, University of Miami Coral Gables Florida USA murthy1@miami.edu.
  • Ramamurthy V; Department of Chemistry, University of Miami Coral Gables Florida USA murthy1@miami.edu.
  • Elles CG; Department of Chemistry, University of Kansas Lawrence Kansas USA elles@ku.edu.
Chem Sci ; 11(35): 9513-9523, 2020 Aug 24.
Article em En | MEDLINE | ID: mdl-34094217
Ultrafast transient absorption spectroscopy reveals new excited-state dynamics following excitation of trans-azobenzene (t-Az) and several alkyl-substituted t-Az derivatives encapsulated in a water-soluble supramolecular host-guest complex. Encapsulation increases the excited-state lifetimes and alters the yields of the trans → cis photoisomerization reaction compared with solution. Kinetic modeling of the transient spectra for unsubstituted t-Az following nπ* and ππ* excitation reveals steric trapping of excited-state species, as well as an adiabatic excited-state trans → cis isomerization pathway for confined molecules that is not observed in solution. Analysis of the transient spectra following ππ* excitation for a series of 4-alkyl and 4,4'-dialkyl substituted t-Az molecules suggests that additional crowding due to lengthening of the alkyl tails results in deeper trapping of the excited-state species, including distorted trans and cis structures. The variation of the dynamics due to crowding in the confined environment provides new evidence to explain the violation of Kasha's rule for nπ* and ππ* excitation of azobenzenes based on competition between in-plane inversion and out-of-plane rotation channels.

Texto completo: 1 Coleções: 01-internacional Base de dados: MEDLINE Idioma: En Ano de publicação: 2020 Tipo de documento: Article

Texto completo: 1 Coleções: 01-internacional Base de dados: MEDLINE Idioma: En Ano de publicação: 2020 Tipo de documento: Article