1. Electrochemistry and Photophysics of Donor-Substituted Triarylboranes: Symmetry Breaking in Ground and Excited State
- Author
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Christoph Lambert, Rüdiger Wortmann, Ruth Jakober, Conrad Kaiser, and Rainer Stahl
- Subjects
Ultraviolet visible spectroscopy ,Chemistry ,Absorption band ,Excited state ,Organic Chemistry ,Solvatochromism ,General Chemistry ,Cyclic voltammetry ,Photochemistry ,Absorption (electromagnetic radiation) ,Catalysis ,Fluorescence spectroscopy ,Excitation - Abstract
We synthesized a series of amino substituted triarylboranes (TABs) 1-3 by copper(I)-catalyzed cross-coupling reactions. The title compounds were investigated by means of cyclic voltammetry (CV) and UV-visible absorption and fluorescence spectroscopy. Electrochemical oxidation of tris(4-carbazolyl-2,6-dimethylphenyl)-borane (3) leads to the formation of an electroactive polymer film on the electrode surface. The charge-transfer (CT) absorption band of all three TABs shows a pronounced negative solvatochromism, while the emission is positively solvatochromic. By combining Jortner's theory, AMI computations, and electrooptical absorption measurements (EOAM), this unexpected behavior was shown to be due to a dipole inversion upon S 0 →S 1 excitation. Furthermore, polarized steady-state fluorescence spectroscopy and EOAM prove that the ground-state geometry of 3 is of lower symmetry than D 3 and that the excitation energy can be transferred from one subchromophore to another within the lifetime of the excited state. Exciton-coupling theory was used to quantitatively analyze this excitation transfer.
- Published
- 2006
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