Document Detail

Symmetry-dependent solvation of donor-substituted triarylboranes.
MedLine Citation:
PMID:  18936848     Owner:  NLM     Status:  MEDLINE    
Donor-substituted triarylboranes are investigated by femtosecond absorption spectroscopy to study the influence of molecular symmetry on solvation. In solvents of varying polarity and differently fast solvation response, the solvation dynamics of a highly symmetric triple carbazole-substituted triarylborane (TCB) is compared to a single carbazole-substituted triarylborane (CB). The decomposition of the transient absorption spectra allows us to measure the solvation time by means of the time-dependent solvatochromic shift of the excited-state absorption (ESA) and the stimulated emission (SE). For all polar solvents under study we find an accelerated solvation process for TCB compared to the less symmetric CB. The difference is particularly large for solvents with a slow response. In order to explain these findings we propose that the electronic excitation is mobile in the symmetric molecule and can change between the three carbazole chromophores probably by a hopping mechanism. The excited-state dipole moment of TCB can thereby respond to the solvent relaxation and changes its direction according to the local field of the solvation shell. Thus, in a symmetric solute the possibility of an intramolecular charge delocalization over equivalent sites accelerates the approach of the minimum-energy configuration.
Uwe Megerle; Florian Selmaier; Christoph Lambert; Eberhard Riedle; Stefan Lochbrunner
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2008-09-09
Journal Detail:
Title:  Physical chemistry chemical physics : PCCP     Volume:  10     ISSN:  1463-9076     ISO Abbreviation:  Phys Chem Chem Phys     Publication Date:  2008 Nov 
Date Detail:
Created Date:  2008-10-21     Completed Date:  2008-12-31     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  100888160     Medline TA:  Phys Chem Chem Phys     Country:  England    
Other Details:
Languages:  eng     Pagination:  6245-51     Citation Subset:  IM    
Lehrstuhl für BioMolekulare Optik, Ludwig-Maximilians-Universität München, Oettingenstrasse 67, Munich, Germany.
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MeSH Terms
Boranes / chemistry*
Cyclohexanes / chemistry
Hydrocarbons / chemistry
Methylene Chloride
Models, Molecular
Molecular Conformation
Nitriles / chemistry
Solvents / chemistry
Spectrophotometry, Ultraviolet
Reg. No./Substance:
0/Boranes; 0/Carbazoles; 0/Cyclohexane; 0/Cyclohexanes; 0/Furans; 0/Hydrocarbons; 0/Nitriles; 0/Solvents; 100-47-0/benzonitrile; 109-99-9/tetrahydrofuran; 67-66-3/Chloroform; 75-09-2/Methylene Chloride

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