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Electrochemistry and Photophysics of Donor‐Substituted Triarylboranes: Symmetry Breaking in Ground and Excited State
Author(s) -
Stahl Rainer,
Lambert Christoph,
Kaiser Conrad,
Wortmann Rüdiger,
Jakober Ruth
Publication year - 2006
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200500948
Subject(s) - solvatochromism , excited state , photochemistry , exciton , ground state , chemistry , point reflection , absorption (acoustics) , absorption spectroscopy , excitation , spectroscopy , absorption band , atomic physics , molecular physics , materials science , optics , molecule , physics , condensed matter physics , organic chemistry , quantum mechanics , composite material
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, AM1 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.