Nitrogen-rich pi-conjugated stars - discotic liquid crystals with an electron deficient core

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New discotic liquid crystals displaying broad mesophases, high electron affinity, efficient fluorescence and sensing ability will be synthesized. Electron deficient heterocycles, pyrazine, 1,3,5-triazine, 1,2,4-triazole and 1,3,4-oxadiazole are building blocks for the center of these star- or disc-shaped molecules. A series of alkyl chains is attached as ether, amine or thioether to the rim of the stars to provide solubility and fusibility. Number, position, type and length of the chains are tools to tune the thermal properties; aggregation of pi-segments yields columns and their aliphatic surface should result in broad mesophases. N,O,S are moderate to strong electron donating groups, thus modifying the optical properties. The impact of phase, concentration, polarity and protons on optical spectra as well as non-linear optical properties will be studied. Thermal methods will be used to characterize phase behavior, X-ray diffraction to elucidate structures of the LC-phases. As potential new n-type semiconductors and emitters in OLEDs, electrical studies will be performed. Some stars will be substrates for reactions converting arylene fragments to annulated heterocyclic systems. Cadogan reaction reduces o-nitrobiaryl units to heteroanalogous carbazoles, 1,2-diarylarenes will be oxidized in a Scholl reaction and oxidative photocyclisation transforms vicinal distyrylarenes to extended condensed heterocyclic aromatic systems. s-Heptazine, a unique fluorophore, will be introduced as a new core for hekates.