- Luminescent columnar liquid crystals based on 1,3,4-oxadiazole
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In this study five new compounds, derivatives of 1,3,4-oxadiazole, were synthesized in order to achieve mesomorphic behavior and luminescence. Different types of aliphatic chains were used in order to investigate the influence of alkoxide groups in mesomorphic behavior. All of the compounds showed high thermal stability and strong blue photoluminescence in solution and in solid films. Furthermore, compounds 10a-d presented hexagonal columnar mesomorphism, which was characterized by polarizing optical microscopy and X-ray diffraction, and strong π-stacking was observed. Notably, for two compounds (10c,d), the liquid crystal properties were preserved on cooling from the isotropic state to room temperature. These characteristics make these materials good candidates for application in organic electronics.
- Girotto, Edivandro,Eccher, Juliana,Vieira, André A.,Bechtold, Ivan H.,Gallardo, Hugo
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supporting information
p. 3355 - 3360
(2014/05/06)
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- Bidirectional Association of Branched Noncovalent Complexes of Tetrazoles and 1,3,5-Tris(4,5-dihydroimidazol-2-yl)benzene in Solution
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Noncovalent 3:1 complexes were obtained by combining acidic tetrazoles with the tribasic 1,3,5-tris(4,5-dihydroimidazol-2-yl)benzene (1). A branched structure and the use of solubilizing groups ensured that the resulting complexes dissolved in a range of nonpolar organic solvents. An X-ray crystal structure analysis of a model complex with tetrazole showed a completely planar, C3-symmetrical, hydrogen-bonded molecule that salt-packed along the crystallographic c axis with an interplanar spacing of 3.31 A. Model binding studies between a tetrazolate and a protonated 1,3-bis(4,5-dihydroimidazol-2-yl)benzene allowed an association constant of 2470 ± 400 M-1 to be measured in the competitive solvent mixture CDCl3/CD3OD (97:3). The ionic nature and the extended planarity of the tetrazole complexes' core favored the formation of supramolecular stacks not only in the solid, but also in (nonpolar) solution. Self-association was evidenced by NMR and CD spectroscopy as well as by vapor-pressure osmometry.
- Kraft, Arno,Osterod, Frank,Froehlich, Roland
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p. 6425 - 6433
(2007/10/03)
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