A new fluorophore containing 2,1,3-benzothiadiazole unit with alkylated tetrazole terminal groups as electron donors connected through a π-conjugated system of the type (D-π-A-π-D) was synthesized using the Sonogashira coupling reaction with good yields. The genotoxicity of the two intermediate compounds and the final product was evaluated in vitro in consideration of the potential application of the new compound in the chemical production of photovoltaic paints. The new fluorophore did not show significant biological effects in the cell viability test and the comet assay when compared with the intermediate compounds that were obtained synthetically despite the ability to interact with deoxyribonucleic acid (DNA) as demonstrated in circular dichroism assays. Thus, the compound does not show toxic or genotoxic activity, and therefore, it can be applied as a pigment in photovoltaic paint.

Two new thiourea derivatives were synthesized through the reaction of photoactive aminohydroxybenzazoles and p-isothiocyanate benzoic acid via nucleophilic addition reaction. The compounds were characterized using high resolution mass spectrometry with eletrospray ionization (HRMS-ESI), Fourier transform infrared (FTIR), 13C and 1H nuclear magnetic resonance (NMR) spectroscopies. UV-Vis and steady-state fluorescence in solution were also applied to characterize their photophysical behavior. The compounds present absorption in the ultraviolet region (ca. 300 nm) and fluorescence emission with a large Stokes' shift in the UV-A and green region, with the longer wavelength related to phototautomerism in the excited state (ESIPT). Both compounds were investigated as optical sensors for the detection of anions in solution, presenting a potential application for fluoride ion detection by naked-eye and UV-Vis spectroscopy. The continuous variation method plot gave a 1:1 stoichiometric ratio between the chemosensors and F- for the new formed species. The UV-Vis and 1H NMR titration experiments reflect the establishment of a hydrogen bond interaction between the thiourea moiety of the chemosensors and fluoride. In addition, the presence of fluoride in solution tailored the fluorescence emission of one compound favoring the ESIPT emission.

Uma série de quatro compostos fotoativos derivados da triazina foi obtida a partir da substituição nucleofílica aromática no cloreto cianúrico. Os compostos foram caracterizados por espectroscopia de infravermelho (IR) e ressonância magnética nuclear (NMR de ¹H e 13C), além de espectrometria de massas de alta resolução (HRMS MALDI). A espectroscopia de absorção na região do UV-Vis e a emissão de fluorescência (no estado sólido e em solução) foram também utilizadas para estudar o comportamento fotofísico destes compostos. Os derivados obtidos são fluorescentes na região do azul-laranja por um mecanismo de transferência protônica intramolecular no estado excitado e apresentam um grande deslocamento de Stokes (6365-10290 cm-1). Os derivados sintetizados neste trabalho reagiram com sucesso com fibras de celulose para dar novos compostos celulósicos fluorescentes.

Four new reactive fluorescent triazine derivatives were obtained from nucleophilic aromatic substitution of cyanuric chloride. The compounds were characterized by infrared spectroscopy (IR), nuclear magnetic resonance (13C and ¹H NMR) and high resolution mass spectrometry (HRMS MALDI). UV-Vis and steady-state fluorescence (in solution and in solid state) spectroscopies were also applied to characterize the photophysical behavior. The dyes are fluorescent by an intramolecular proton transfer mechanism (ESIPT) in the blue-orange region, with a large Stokes shift between 6365-10290 cm-1. The fluorescent cyanuric derivatives could successfully react with cellulose fibers to give new fluorescent cellulosic materials.

Uma série de calcogeno ésteres, 1a, 6a e 6b foi obtida em uma rota sintética conveniente. A análise de microscopia óptica de luz polarizada (POM) e calorimetria diferencial de varredura (DSC) mostrou que estes calcogeno ésteres apresentam uma ampla faixa de mesofase nemática. Além disso, espectros de absorção na região do UV-Vis em solução (ca.10-5 mol L-1) também foram obtidos de maneira a se obter a diferença de energia entre os orbitais moleculares HOMO-LUMO, para posterior comparação com os resultados teóricos. Os valores calculados para o gap de HOMO-LUMO estão de acordo com os valores experimentais obtidos, onde a eletronegatividade do heteroátomo (O, S e Se) deve ser o principal fator para a localização do máximo de absorção. Um estudo teórico foi realizado utilizando cálculos de DFT/B3LYP com método híbrido de Becke aplicando uma correlação funcional de Lee-Yang-Parr (B3LYP) com a base DGDZVP a fim de avaliar algumas propriedades físico-químicas relacionadas com o mesomorfismo e as propriedades eletrônicas espectrais. Através da síntese destes compostos, a influência do átomo de calcogênio nas propriedades fotofísicas e mesomórficas pôde ser avaliada de uma forma mais precisa.

A series of chalcogeno esters 1a, 6a and 6b have been synthesized in a straightforward manner. Polarized-light optical microscopy (POM) and differential scanning calorimetry (DSC) showed that these chalcogeno esters displayed a wide nematic range of mesophase. In addition, UV-Vis in solution (ca.10-5 mol L-1) was applied in order to obtain the HOMO-LUMO gap for further comparison with the theoretical results. The calculated values to the HOMO-LUMO gap are in excellent agreement with the experimental results, where the electronegativity of the heteroatom (O, S and Se) seems to play a fundamental role in the absorption maxima location. A theoretical study was performed using a DFT/B3LYP calculations with Becke's three-parameter hybrid method applying the Lee-Yang-Parr functional correlation (B3LYP) with DGDZVP basis set in order to evaluate some physical chemistry data related with mesomorphic and spectral eletronic properties. By synthesizing these compounds we were able to get a more precise description about the influence of the chalcogen atom on the mesomorphic and photophysical properties.