Initial processes of proton transfer in salicylideneaniline studied by time-resolved photoelectron spectroscopy

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Journal titleJournal of Physical Chemistry A
Pages29712979; # of pages: 9
SubjectExcitation wavelength; Excited state reactions; Excited-state dynamics; Excited-state intramolecular proton transfer; Femtosecond time-resolved; Ground-state molecules; Time dependent density functional theory; Time-resolved photoelectron spectroscopy; Density functional theory; Excited states; Photoelectron spectroscopy; Proton transfer; Ground state; aniline derivative; salicylideneaniline; X ray photoelectron spectroscopy; Aniline Compounds; Quantum Theory; Schiff Bases
AbstractExcited-state intramolecular proton transfer (ESIPT) in salicylideneaniline (SA) and selected derivatives substituted in the para position of the anilino group have been investigated by femtosecond time-resolved photoelectron spectroscopy (TRPES) and time-dependent density functional theory (TDDFT). SA has a twisted structure at the energetic minimum of the ground state, but ESIPT is assumed to take place through a planar structure, although this has not been fully established. The TRPES studies revealed that the excited-state dynamics within the S1 band varied significantly with excitation wavelength. At finite temperatures, the ground state was found to sample a broad range of torsional angles, from planar to twisted. At lower photon energies (370 nm), only the planar ground-state molecules were excited, and the excited-state reaction took place within 50 fs. At higher energies (350 and 330 nm), predominantly twisted ground-state molecules were excited: they had to planarize before ESIPT could occur. This process was found to be slower in methylated SA but did not change significantly in the brominated and nitrated SAs. These substitution effects on the decay dynamics can be explained by modifications of the potential barriers, as predicted by the TDDFT calculations, and support the mechanism of a twisting motion of the anilino ring prior to ESIPT. The contribution of another pathway leading to internal conversion within the enol form was found to be minor at the excitation wavelengths considered here.
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AffiliationSecurity and Disruptive Technologies; National Research Council Canada
Peer reviewedYes
NPARC number21270507
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Record identifierdff91493-9513-407a-a06f-0888e78bd660
Record created2014-02-14
Record modified2016-05-09
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