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Issue 44, 2015
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Controllable molecular aggregation and fluorescence properties of 1,3,4-oxadiazole derivatives

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Abstract

The molecular self-assembly behaviour of 2,2′-bis-(4-hexyloxyphenyl)-bi-1,3,4-oxadiazole (BOXD-6) in solution, on surfaces and in bulk crystals, and its photo-physical properties were studied via a combination of experimental techniques and theoretical calculations. It is found that BOXD-6 molecules self-assemble into both H- and J-aggregates at moderate concentration (∼10−4 M) and then transit to exclusive J-aggregates at higher concentration (∼10−3 M) in tetrahydrofuran. In H-aggregation (α polymorph), BOXD-6 adopts a linear conformation and forms a one-dimensional layered structure; in J-aggregation (β polymorph), it adopts a Z-shaped conformation and forms a more ordered two-dimensional layered structure. A π-stacking structure is observed in both cases, and adjacent molecules in J-aggregation show larger displacement along the molecular long axis direction than that in H-aggregation. Although J-aggregates are almost the only component in concentrated solutions (10−3 M), both H- and J-aggregates can be obtained if concentrated solution is transformed onto substrates through a simple drop-casting method. Such a phase transition during film formation can be easily avoided by adding water as a precipitator; a film with pure J-aggregates is then obtained. In order to get more information on molecular self-assembly, intermolecular interaction potential energy surfaces (PES) were evaluated via theoretical calculations at the DFT level (M062x/6-31G**). The PES not only confirm the molecular stacking structures found in crystals but also predict some other likely structures, which will be the target of future experiments.

Graphical abstract: Controllable molecular aggregation and fluorescence properties of 1,3,4-oxadiazole derivatives

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Publication details

The article was received on 06 Aug 2015, accepted on 13 Oct 2015 and first published on 14 Oct 2015


Article type: Paper
DOI: 10.1039/C5TC02445E
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J. Mater. Chem. C, 2015,3, 11681-11688
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    Controllable molecular aggregation and fluorescence properties of 1,3,4-oxadiazole derivatives

    H. Wang, F. Chen, X. Jia, H. Liu, X. Ran, M. K. Ravva, F. Bai, S. Qu, M. Li, H. Zhang and J. Brédas, J. Mater. Chem. C, 2015, 3, 11681
    DOI: 10.1039/C5TC02445E

    This article is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported Licence. Material from this article can be used in other publications provided that the correct acknowledgement is given with the reproduced material and it is not used for commercial purposes.

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