title: Ultrafast Time-Resolved Spectroscopy of Diarylethene-Based Photoswitchable Deoxyuridine Nucleosides.
abstract: Photoswitches based on the diarylethene architecture have been attracting considerable attention for the investigation and control of a variety of biological processes. The reversible photoisomerization reaction between their open- and closed-ring forms can be selectively addressed by irradiation with light of two markedly different wavelengths. In this work, the dynamics of the photochromic ring-opening reaction of four novel diarylethene-based photoswitchable deoxyuridine nucleosides is investigated by femtosecond transient absorption. Upon photoexcitation with sub-20 fs pulses in the first absorption band (500 nm), all four photoswitches showed a fast ballistic excited-state deactivation within less than 500 fs toward the S1/S0 conical intersection. Transient data was globally analyzed, and a relaxation kinetic model with a branching between open and closed ring forms without any loss channels was derived. Ring-opening quantum yields, Φr-o, were found to strongly depend on the substituents (R), ranging from 0.64 (dU(PSI): R = 2-naphthyl) to 0.30 (dU(PSIV): R = 2-pyridyl).
authors.affiliation: Physikalisch Chemisches Institut and ‡Institut für Pharmazie und Molekulare Biotechnologie, Ruprecht-Karls-Universität Heidelberg , D-69120 Heidelberg, Germany.
authors.forename: Tiago
authors.initials: T
authors.lastname: Buckup
authors.affiliation: Physikalisch Chemisches Institut and ‡Institut für Pharmazie und Molekulare Biotechnologie, Ruprecht-Karls-Universität Heidelberg , D-69120 Heidelberg, Germany.
authors.forename: Christopher
authors.initials: C
authors.lastname: Sarter
authors.affiliation: Physikalisch Chemisches Institut and ‡Institut für Pharmazie und Molekulare Biotechnologie, Ruprecht-Karls-Universität Heidelberg , D-69120 Heidelberg, Germany.
authors.forename: Hans-Robert
authors.initials: HR
authors.lastname: Volpp
authors.affiliation: Physikalisch Chemisches Institut and ‡Institut für Pharmazie und Molekulare Biotechnologie, Ruprecht-Karls-Universität Heidelberg , D-69120 Heidelberg, Germany.
authors.forename: Andres
authors.initials: A
authors.lastname: Jäschke
authors.affiliation: Physikalisch Chemisches Institut and ‡Institut für Pharmazie und Molekulare Biotechnologie, Ruprecht-Karls-Universität Heidelberg , D-69120 Heidelberg, Germany.
authors.forename: Marcus
authors.initials: M
authors.lastname: Motzkus
mesh_terms: D003857:Deoxyuridine / Q000737:chemistry*; D009705:Nucleosides / Q000737:chemistry*; D055668:Photochemical Processes; D011789:Quantum Theory; D013057:Spectrum Analysis / Q000379:methods*
chemical_list: D009705:Nucleosides; D003857:Deoxyuridine
keywords: cycloreversion; diarylethene; photochemistry; ring-opening; ultrafast spectroscopy; wavepacket