Tristriazolotriazines (TTTs) with a threefold alkoxyphenyl substitution were prepared and studied by DSC, polarized optical microscopy (POM) and X-ray scattering. Six pentyloxy chains are sufficient to induce liquid-crystalline behavior in these star-shaped compounds. Thermotropicproperties of TTTs with varying substitution patterns and a periphery of linear chains of different lengths, branching
core and a periphery of six to nine alkoxy chains are synthesized via Huisgen reaction. DSC, POM, and TGA give information about the thermal properties of these discotic liquid crystals, XRD enlightens the structures of the very broad mesophases The efficient fluorescence of these discs is positively solvatochromic and strongly influenced by aggregation.
rearrangements drops with each step by a factor of 4, whereas the gain in heat of formation increases. Density functional theory (DFT) calculations led to transition states; their energies correspond to the experimental data. Threefold isomerization strongly affects the mesomorphic properties.
Bidirectional Association of Branched Noncovalent Complexes of Tetrazoles and 1,3,5-Tris(4,5-dihydroimidazol-2-yl)benzene in Solution
作者:Arno Kraft、Frank Osterod、Roland Fröhlich
DOI:10.1021/jo990830z
日期:1999.8.1
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, C-3-symmetrical, hydrogen-bonded molecule that salt-packed along the crystallographic c axis with an interplanar spacing of 3.31 Angstrom. 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.