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Hydrogen‐Bond Dynamics and Solvation of Electronically Excited States as Determined by Femtosecond Vibrational Spectroscopy
Author(s) -
Nibbering Erik T.J.,
Chudoba Christian,
Elsaesser Thomas
Publication year - 1999
Publication title -
israel journal of chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.908
H-Index - 54
eISSN - 1869-5868
pISSN - 0021-2148
DOI - 10.1002/ijch.199900040
Subject(s) - chemistry , solvation , hydrogen bond , photochemistry , chromophore , excited state , molecule , femtosecond , intermolecular force , acceptor , spectroscopy , chemical physics , computational chemistry , atomic physics , organic chemistry , laser , physics , quantum mechanics , optics , condensed matter physics
Abstract The ultrafast dynamics of site‐specific hydrogen bonds between an organic chromophore serving as hydrogen acceptor and a hydrogen‐donating species in solution is studied by femtosecond vibrational spectroscopy. This new method gives specific insight into microscopic structural changes of hydrogen bonds initiated by electronic excitation of the chromophore. We study H‐bonded complexes of coumarin 102 with the solvent CHCl 3 , and with phenol. Upon electronic excitation, the intermolecular hydrogen bond between proton donor and acceptor is cleaved within 200 fs, followed by a slower reorientation dynamics of the donor molecules extending into the picosecond regime. For CHCl 3 , this slower rearrangement is interpreted in terms of polar solvation. In complexes consisting of a coumarin molecule and two phenol moieties, the slower dynamics is related to geometry changes of the phenol–phenol hydrogen bond. The consequences of those results for a microscopic picture of polar solvation are discussed.