Luminescent Mono-, Di-, and Triradicals: Bridging Polychlorinated Triarylmethyl Radicals by Triarylamines and Triarylboranes |
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| Authors: | Dr Yohei Hattori Evripidis Michail Alexander Schmiedel Michael Moos Dr Marco Holzapfel Dr Ivo Krummenacher Prof Holger Braunschweig Ulrich Müller Prof Jens Pflaum Prof Christoph Lambert |
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| Institution: | 1. Institute of Organic Chemistry, Julius-Maximilians-University Würzburg, Am Hubland, 97074 Würzburg, Germany;2. Institute of Inorganic Chemistry, Julius-Maximilians-University Würzburg, Am Hubland, 97074 Würzburg, Germany;3. Institute of Physics, Julius-Maximilians-University Würzburg, Am Hubland, 97074 Würzburg, Germany |
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| Abstract: | Up to three polychlorinated pyridyldiphenylmethyl radicals bridged by a triphenylamine carrying electron withdrawing (CN), neutral (Me), or donating (OMe) groups were synthesized and analogous radicals bridged by tris(2,6-dimethylphenyl)borane were prepared for comparison. All compounds were as stable as common closed-shell organic compounds and showed significant fluorescence upon excitation. Electronic, magnetic, absorption, and emission properties were examined in detail, and experimental results were interpreted using DFT calculations. Oxidation potentials, absorption and emission energies could be tuned depending on the electron density of the bridges. The triphenylamine bridges mediated intramolecular weak antiferromagnetic interactions between the radical spins, and the energy difference between the high spin and low spin states was determined by temperature dependent ESR spectroscopy and DFT calculations. The fluorescent properties of all radicals were examined in detail and revealed no difference for high and low spin states which facilitates application of these dyes in two-photon absorption spectroscopy and OLED devices. |
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| Keywords: | density functional calculations fluorescence NIR OLED radical two-photon absorption |
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