Materiais moleculares funcionais contendo n-heterociclos - capes

XVIIABSTRACTThe synthesis and characterization of new functional materials based on highly π-conjugatedmolecules containing N-hetorocycles are described. Such molecules have been designed inorder to exhibit semiconducting and luminescent properties, as well as liquid crystallinephases and/or stable thin film forming behaviour. The thermal properties were evaluated byDSC, TGA and polarizing optical microscopy. The optical properties were investigated bytheir absorption and emission spectra. This thesis presents 4 series of compounds: 1) liquidcrystals containing the heterocycle 1,3,4-oxadiazole with a similar hockey stick molecularshape. The core containing the heterocycle is linked to different aromatic moieties by acarbon-carbon triple bond using Sonogashira’s coupling reaction. These compounds exhibitednematic and smectic LC phases, typical of calamitic compounds, and also strong bluefluorescence; 2) liquid crystals based on the bent core of 1,4-disubstituted-[1,2,3]-triazoleprepared through click-reaction, 1,3-dipolar cycloaddition of an aromatic azide to differentterminal arylacetylenes. They showed preferentially SmC phase in a wide range oftemperature and weak fluorescence in solution; 3) V-shaped molecular soft materialscontaining the central core 2,3-dicyanopyrazine. The final compounds were obtained byestherification reaction between the diphenol, containing the heterocycle, and differentaromatic carboxylic acids. These compounds were not liquid crystals and, the non-planarity,also confirmed by the X-ray crystalline structure, led to a intrinsic transparent film formingproperty. Due to different molecular packing in solid phase such compounds exhibitedfluorescence in a wide range of the spectrum (from blue to green); 4) Discotic molecular softmaterials based on the heterocycle tris-[1,2,4]-triazolo-[1,3,5]-triazines (TTT) is proposed as anew core for discotic LCs, and was synthesized by the reaction between aryltetrazoles andcyanuric chloride. After melting, such compounds do not crystallize remaining in a supercooledstate. Consequently stable films are achievable. All these final compounds exhibitedstrong blue fluorescence. The chemical structure of the heterocycle TTT was totallycharacterized, including 15 N NMR, theoretical calculations and X-ray difractometry analysis,which confirmed definitely the isomeric form of the triazole ring. A discotic LC containingthe core TTT and showing a columnar hexagonal phase was synthesized and characterized. Astudy of charge transporting in the hexagonal columnar phase of this compound is alsodescribed.