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Abstract We introduce a new boron‐doped cyclophane, the hexabora[16]cyclophaneB6‐FMes, in which six tricoordinate borane moieties alternate with short conjugatedp‐phenylene linkers. Exocyclic 2,4,6‐tris(trifluoromethyl)phenyl (FMes) groups serve not only to further withdraw electron density but at the same time sterically shield the boron atoms, resulting in a macrocycle that is both highly electron‐deficient and stable. The optical and electronic properties are compared with those of related linear oligomers and the electronic structure is further evaluated by computational methods. The studies uncover unique properties ofB6‐FMes, including a low‐lying and extensively delocalized LUMO and a wide HOMO–LUMO gap, which arise from the combination of a cyclic π‐system, strong electronic communication between the closely spaced borons, and the attachment of electron‐deficient pendent groups. The binding of small anions to the electron‐deficient macrocycle and molecular model compounds is investigated and emissive exciplexes are detected in aromatic solvents.
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Effect of methoxy-substitutions on the hole transport properties of carbazole-based compounds: pros and cons
We have recently reported the role of methoxy substitutions on the optoelectronic properties of two new series of carbazole–bridge–carbazole compounds (bridge = carbazole, phenyl) by varying the number of methoxy groups from 0–4 per carbazole unit. Here, we report the effect of molecular shape (linear versus V-shape), number and linking topology of the methoxy-substitutions on the hole-transport properties of these molecules. The results indicate a delicate balance between the positive and negative effects depending on the substitution topology and the nature of the bridge. It is found that, unlike recent findings from our groups, the methoxy substituents in these compounds reduce the hole mobilities due to the enhanced molecular polarity, a detrimental effect which can be importantly reduced by designing linear D–A–D architectures. The differences in the geometries of the new compounds and their hole transport properties as a function of the nature of the bridge, number of methoxy groups and the substitution topology are explained in terms of the different symmetry of HOMO and HOMO−1 of the carbazole units, which interact very differently with the methoxy substituents and the bridge (carbazole or phenyl). The pros and cons of using- versus -avoiding methoxy groups in order to improve the hole mobility of the new compounds are discussed with regard to the targeted application.
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- Award ID(s):
- 1955299
- PAR ID:
- 10285190
- Date Published:
- Journal Name:
- Journal of Materials Chemistry C
- ISSN:
- 2050-7526
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/D1TC02000E
