Solvent-dependent excited-state hydrogen transfer and intersystem crossing in 2-(2′-hydroxyphenyl)-benzothiazole
AuthorsAly, Shawkat Mohammede
Hamdi, Ghada A.
Mohammed, Omar F.
KAUST DepartmentChemical Science Program
KAUST Solar Center (KSC)
Physical Science and Engineering (PSE) Division
Ultrafast Laser Spectroscopy and Four-dimensional Electron Imaging Research Group
Online Publication Date2014-11-03
Print Publication Date2015-02-12
Permanent link to this recordhttp://hdl.handle.net/10754/564055
MetadataShow full item record
AbstractThe excited-state intramolecular hydrogen transfer (ESIHT) of 2-(2′-hydroxyphenyl) benzothiazole (HBT) has been investigated in a series of nonpolar, polar aprotic, and polar protic solvents. A variety of state-of-the-art experimental methods were employed, including femto- and nanosecond transient absorption and fluorescence upconversion spectroscopy with broadband capabilities. We show that the dynamics and mechanism of ESIHT of the singlet excited HBT are strongly solvent-dependent. In nonpolar solvents, the data demonstrate that HBT molecules adopt a closed form stabilized by O-H⋯N chelated hydrogen bonds with no twisting angle, and the photoinduced H transfer occurs within 120 fs, leading to the formation of a keto tautomer. In polar solvents, owing to dipole-dipole cross talk and hydrogen bonding interactions, the H transfer process is followed by ultrafast nonradiative deactivation channels, including ultrafast internal conversion (IC) and intersystem crossing (ISC). This is likely to be driven by the twisting motion around the C-C bond between the hydroxyphenyl and thiazole moieties, facilitating the IC back to the enol ground state or to the keto triplet state. In addition, our femtosecond time-resolved fluorescence experiments indicate, for the first time, that the lifetime of the enol form in ACN is approximately 280 fs. This observation indicates that the solvent plays a crucial role in breaking the H bond and deactivating the excited state of the HBT. Interestingly, the broadband transient absorption and fluorescence up-conversion data clearly demonstrate that the intermolecular proton transfer from the excited HBT to the DMSO solvent is about 190 fs, forming the HBT anion excited state.
SponsorsS.M.A. is grateful for the postdoctoral fellowship provided by Saudi Basic Industries Corporation (SABIC). The work reported here was supported by the King Abdullah University of Science and Technology.
PublisherAmerican Chemical Society (ACS)
- Ultrafast branching of reaction pathways in 2-(2'-hydroxyphenyl)benzothiazole in polar acetonitrile solution.
- Authors: Mohammed OF, Luber S, Batista VS, Nibbering ET
- Issue date: 2011 Jul 7
- The effect of hydrogen bonding on the excited-state proton transfer in 2-(2'-hydroxyphenyl)benzothiazole: a TDDFT molecular dynamics study.
- Authors: Kungwan N, Plasser F, Aquino AJ, Barbatti M, Wolschann P, Lischka H
- Issue date: 2012 Jul 7
- Ultrafast dynamics of the excited states of curcumin in solution.
- Authors: Ghosh R, Mondal JA, Palit DK
- Issue date: 2010 Sep 23
- Probing the effect of solvation on photoexcited 2-(2'-hydroxyphenyl)benzothiazole via ultrafast Raman loss spectroscopic studies.
- Authors: Kayal S, Roy K, Lakshmanna YA, Umapathy S
- Issue date: 2018 Jul 28
- Ultrafast internal conversion pathway and mechanism in 2-(2'-hydroxyphenyl)benzothiazole: a case study for excited-state intramolecular proton transfer systems.
- Authors: Barbatti M, Aquino AJ, Lischka H, Schriever C, Lochbrunner S, Riedle E
- Issue date: 2009 Mar 7