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Issue 41, 2008
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Symmetry-dependent solvation of donor-substituted triarylboranes

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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.

Graphical abstract: Symmetry-dependent solvation of donor-substituted triarylboranes

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Publication details

The article was received on 11 Apr 2008, accepted on 03 Jul 2008 and first published on 09 Sep 2008

Article type: Paper
DOI: 10.1039/B806131A
Phys. Chem. Chem. Phys., 2008,10, 6245-6251

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    Symmetry-dependent solvation of donor-substituted triarylboranes

    U. Megerle, F. Selmaier, C. Lambert, E. Riedle and S. Lochbrunner, Phys. Chem. Chem. Phys., 2008, 10, 6245
    DOI: 10.1039/B806131A

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