Controllable molecular aggregation and fluorescence properties of 1,3,4-oxadiazole derivative
Ravva, Mahesh Kumar
KAUST DepartmentPhysical Sciences and Engineering (PSE) Division
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AbstractThe 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 form a more ordered two-dimensional layered structure. A π-stacking structure is observed in both cases, and adjacent molecules in the 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 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.
CitationControllable molecular aggregation and fluorescence properties of 1,3,4-oxadiazole derivative 2015 J. Mater. Chem. C
SponsorsAuthor H.W. would like to thank Dr Jian Wang (Jilin University) for technical assistance. This work was supported by the National Science Foundation of China (51103057, 51073071, 21173096, 61274126, and 21003057), the Postdoctoral Science Foundation of China (2012T50294) and King Abdullah University of Science and Technology.
PublisherRoyal Society of Chemistry (RSC)
JournalJ. Mater. Chem. C
Is Supplemented ByWang, H., Chen, F., Jia, X., Liu, H., Ran, X., Ravva, M. K., … Brédas, J.-L. (2015). CCDC 1018247: Experimental Crystal Structure Determination [Data set]. Cambridge Crystallographic Data Centre. https://doi.org/10.5517/cc135kpj
Wang, H., Chen, F., Jia, X., Liu, H., Ran, X., Ravva, M. K., … Brédas, J.-L. (2015). CCDC 1018246: Experimental Crystal Structure Determination [Data set]. Cambridge Crystallographic Data Centre. https://doi.org/10.5517/cc135knh