New Fluorescence Domain “Excited Multimer” Formed upon Photoexcitation of Continuously Stacked Diaroylmethanatoboron Difluoride Molecules with Fused π‐Orbitals in Crystals |
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Authors: | Atsushi Sakai Dr Eisuke Ohta Yuichi Yoshimoto Mirai Tanaka Dr Yasunori Matsui Prof?Dr Kazuhiko Mizuno Prof?Dr Hiroshi Ikeda |
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Institution: | 1. Department of Applied Chemistry, Graduate School of Engineering, Osaka Prefecture University, Sakai, Osaka 599‐8531 (Japan);2. The Research Institute for Molecular Electronic Devices (RIMED), Osaka Prefecture University, Sakai, Osaka 599‐8531 (Japan) |
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Abstract: | The crystal‐packing structures of seven derivatives of diaroylmethanatoboron difluoride ( 1 a – gBF2 ) are characterized by no overlap of the π‐conjugated main units of two adjacent molecules (type I), overlap of the benzene ring π‐orbitals of two adjacent molecules (type II), and overlap of the benzene and dihydrodioxaborinine rings π‐orbitals of adjacent molecules (type III). The crystal‐packing structures govern the fluorescence (FL) properties in the crystalline states. The FL domain that is present in type I crystals, in which intermolecular orbital interactions are absent, leads to excited monomer‐like FL properties. In the case of the type II crystals, the presence of intermolecular overlap of the benzene rings π‐orbitals generates new FL domains, referred to as “excited multimers”, which possess allowed S0–S1 electronic transitions and, as a result, similar FL lifetimes at longer wavelengths than the FL of the type I crystals. Finally, intermolecular overlap of the benzene and dihydrodioxaborinine ring π‐orbitals in the type III crystals leads to “excited multimer” domains with forbidden S0–S1 electronic transitions and longer FL lifetimes at similar wavelengths as that in type I crystals. |
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Keywords: | aggregation electronic structure fluorescence spectroscopy organoboron complexes solid‐state structures |
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