The synthesis and structural, thermal, optical and theoretical characterization of new tris[1,2,4]triazolo[1,3,5]triazines were performed to support their application as liquid crystals and advanced materials.

Five discotic molecules comprising a tris[1,2,4]triazolo[1,3,5] triazine core were designed and synthesized to obtain luminescent and charge-transporting columnar liquid crystalline materials. With the exception of one compound containing terminal hydroxyl groups all compounds presented a wide thermal range and stable columnar liquid crystalline phase, characterized by differential scanning calorimetry, polarized optical microscopy, and X-ray diffraction (XRD) techniques. The phase formation appeared to be associated to some extent with interdigitation of the alkoxy and benzylalkoxy portion, as suggested by the XRD results. All compounds have a strong blue luminescence in solution and solid phase. At the temperature at which the compounds enter in the mesophase the luminescence decreases significantly. This result suggests that entrance into the Col(h) phase is accompanied by a better π-stacking of the peripheral phenyl rings compared to the solid phase, consistent with the intramolecular distances (3.5 Å) observed in the XRD analysis. These compounds based on tristriazolotriazine are quite robust with good optical and thermal properties for application as solid state emitters, and we anticipate that they may provide an interesting alternative to other discotic molecules based on N-heterocycles, which generally present a high-temperature Col(h) phase.

Five new V-shaped acids derived from 1,3,4-oxadiazole are described. These compounds were used to prepare supramolecular complexes via hydrogen bonding interactions with 2,4-diamino-6dodecylamino-1,3,5-triazine in a 3 : 1 ratio. The formation of the complexes was evidenced by infrared and NMR techniques. All the complexes were studied by polarizing optical microscopy, differential scanning calorimetry and small-angle X-ray diffraction. Rectangular and hexagonal columnar mesophases were observed for the complexes at room temperature, without signs of crystallization. Circular dichroism studies demonstrated that, in the liquid crystalline state, these materials show supramolecular optical activity. It is proposed that this phenomenon arises due to a helical columnar organization. Furthermore, the complexes display strong blue light emission in solution, with good photoluminescence quantum yields, and in the mesophase. These materials could therefore be promising candidates for optoelectronic applications.

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Although the double Friedel-Crafts acylation of arenes with ethyl chloroglyoxylate is hindered by the strongly deactivating effect of the first-entering glyoxylic substituent, the double reaction is successful with the reactive arene perylene under long reaction times and with concomitant ester hydrolysis. The reaction is regiospecific, giving the 3,9-regioisomer exclusively. This perylenylenediglyoxylic acid is condensed first with o-bromophenylacetic acid and then with α-branched alkylamines to yield the title compounds. Whilst the corresponding tetraalkyl esters only show monotropic mesophases, these diimides show enantiotropic columnar mesophases that can be maintained at room temperature if racemically branched alkyl chains of moderate size are used. A palladium-induced C-C bond migration during the build-up of the arene system leads to an isomeric side product of reduced symmetry that can be isolated by aggregation-controlled chromatographic separation. The HOMO and LUMO energies of the title compounds are considerably higher than those of established perylenetetracarboxdiimides.

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In this study we present the synthesis and complete structural characterization of twenty five 1,3,4oxadiazole molecules (ionic and non-ionic) with some systematic structural variations, such as number of counterions, number of alkoxy chains, alkyl chain size, type of counterion and its position on the molecule.The thermal and photophysical properties for all compounds were investigated allowing a complete and interesting simultaneous study of the effect of structural changes on these properties. We show that every parameter studied affected both the thermal and photophysical properties. For these bent core molecules, the liquid crystalline behavior was observed only for compounds containing one counterion, SmA (monolayer or bilayer) being the predominant phase. The neutral (non-ionic) compounds and the imidazolium derivatives showed emission at around 360 nm and a high quantum yield, while most of the pyridinium derivatives showed emission at around 530 nm, a low quantum yield and a complex photophysical behavior. In all cases, the quantum yield for the different counterions follows the sequence ClO 42 . BF 4 2 . DS 2 . NO 3 2 . Br 2 (I 2 ).