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Flavylium/Chalcone-based molecular switches comprise features such as pH-gated photochromism and fluorescence properties that make them attractive for many applications, ranging from stimuli-responsive materials to photopharmacology. However, in contrast to other common photoswitches, the application of flavylium compounds in these areas remains largely unexplored. Among other possible reasons, this may be due to the lack of general strategies to attach these molecules to substrates such as polymers, nanoparticles, biomolecules, or surfaces. In this work, we have shown that a copper (I) catalyzed azide-alkyne cycloaddition (CuAAC) can be employed to obtain a chalcone conjugate. We used an isosorbide carbohydrate to demonstrate this strategy and investigated the photochemical properties of the chalcone-isosorbide conjugate. The obtained results show that the photochemical properties of this new compound are similar to other equivalent flavylium/chalcone photoswitches, confirming the feasibility of the conjugation strategy.

The ever-growing global energy consumption is making the quest for renewable energy sources one of the most important R&D topics. In this context, Dye-Sensitized Solar Cells (DSSCs) are a major player using cheap and environmentally friendly raw materials and pro-cesses. The use of natural/bio-inspired pigments as sensitizers in DSSCs has come to be a worthwhile substitute to inorganic/organic sensitizers due to their higher cost-effectiveness and reduced environmental pollution risks. The first reported DSSC using natural anthocya-nins displayed a conversion yield of 0.56 % and paved the way for sustainable DSSCs based on renewable resources. However, when considering anthocyanins for DSSC applications, natural extracts are typically directly employed with no concern for optimization of the chem-ical structure of the compounds, resulting in low cell efficiencies. Anchored on the established know-how on anthocyanin and flavylium chemistry of the Photochemistry group of NOVA School of Science and Technology, this thesis proposes to fill that gap. To attain so, the construction of a DSSC lab in the Chemistry Department of the said faculty, fully dedicated to the assembly and characterization of these devices was re-quired. Following this first step, the study of the impact in DSSC performance of selected var-iations in the structure and substitution pattern of a new generation of flavylium dyes was explored. In this work, several bio-inspired anthocyanin and pyranoanthocyanin derivatives were applied as dye sensitizers in DSSCs. The obtained results pointed to important structural aspects of the dyes that determine the power conversion efficiency. These included the influ-ence of the donor group, π-conjugation, structure rigidity, protonation degree and the type of anchoring unit on the adsorption of the dyes to TiO2, and on the overall performance of the devices. Only with this type of comprehensive study one can fully conclude about the potential of this family of compounds for energy applications and demonstrate the importance of fla-vylium-based dyes in the development of future bio-inspired DSSCs. O incessante crescimento do consumo de energia a nível global está a fomentar a importância da pesquisa e desenvolvimento de fontes de energia renováveis. Neste contexto, as Células Solares Sensibilizadas por Corantes (DSSCs) são uma potencial alternativa por dependerem de materiais e processos ‘amigos do ambiente’. O uso de corantes naturais e/ou bio-inspirados como sensibilizadores neste tipo de dispositivos tem vindo a substituir os tradicionais corantes inorgânicos/orgânicos, devido à sua favorável relação ‘custo-benefício’ e reduzido impacto ambiental. O primeiro dispositivo baseado em antocianinas naturais reportou uma eficiência de 0,56 % e trilhou o caminho para DSSCs baseadas em corantes naturais. No entanto, quando as antocianinas são aplicadas em DSSCs, são normalmente utilizados os seus extratos naturais, sem qualquer preocupação com a otimização estrutural das mesmas, resultando em eficiências baixas. Apoiando-se no extenso conhecimento sobre a química de antocianinas e flavílios exis-tente no Grupo de Fotoquímica da FCT NOVA, esta tese propõe-se colmatar essa lacuna. Para tal foi necessária a construção de um laboratório inteiramente dedicado à montagem e carac-terização de DSSCs no Departamento de Química da FCT NOVA. Posteriormente, foi desen-volvido o estudo do impacto de variações específicas na estrutura e padrão de substituição de uma nova geração de sais de flavílio, na performance das DSSCs. Neste trabalho, uma série de derivados de antocianinas e piranoantocianinas bio-inspirados foram aplicados como corantes sensibilizadores em DSSCs. Os resultados obtidos apontam para importantes aspetos estrutu-rais dos corantes que determinam a eficiência de produção de energia. A influência do grupo dador, conjugação π, rigidez estrutural, nível de protonação, e diferentes grupos de ancora-gem, foram estudados e relacionados com a eficiência dos dispositivos. Apenas com este tipo de estudo exaustivo é possível concluir sobre o potencial desta família de compostos para apli-cações em energia. Assim, pretende-se demonstrar a importância de continuamente estudar corantes derivados de flavílios no desenvolvimento de futuras DSSCs bio-inspiradas.

International audience; Two series of flavylium triflates carrying alkoxy side chains in the A-ring (benzo unit of chromylium salt) and thioethers in the B-ring (phenyl unit) (On-Fla-Sm) as well as thioethers at both A- and B-ring (Sn-Fla-Sm) were synthesized in order to understand the effect of thioether functionalization on their self-assembly and electronic properties. Concentration-dependent and diffusion ordered (DOSY) NMR experiments of O1-iV-Fla-S3 indicated the formation of columnar H-aggregates in solution with antiparallel intracolumnar stacking of the AC unit (chromylium) of the flavylium triflate, which agreed with the solid state structure of O1-V-Fla-S1 . Thioether substitution on the B-ring changed the linear optical properties in solution, while it has no effect on the A-ring. According to differential scanning calorimetry, polarizing optical microscopy and X-ray diffraction bulk self-assembly of these ionic liquid crystals (ILCs) depends on the total number of side chains, yielding SmA and LamCol phases for ILCs with 2 - 3 chains and Colro, Colh phases for ILCs with 3 - 6 chains. Thus, we demonstrated that thioethers are a useful design tool for ILCs with tailored properties.

Human lactate dehydrogenase A (hLDHA) is one of the main enzymes involved in the pathway of oxalate synthesis in human liver and seems to contribute to the pathogenesis of disorders with endogenous oxalate overproduction, such as primary hyperoxaluria (PH), a rare life-threatening genetic disease. Recent published results on the knockdown of LDHA gene expression as a safe strategy to ameliorate oxalate build-up in PH patients are encouraging for an approach of hLDHA inhibition by small molecules as a potential pharmacological treatment. Thus, we now report on the synthesis and hLDHA inhibitory activity of a new family of compounds with 2,8-dioxabicyclo[ 3.3.1]nonane core (23–42), a series of twenty analogues to A-type proanthocyanidin natural products. Nine of them (25–27, 29–34) have shown IC50 values in the range of 8.7–26.7 μM, based on a UV spectrophotometric assay, where the hLDHA inhibition is measured according to the decrease in absorbance of the cofactor β-NADH (340 nm). Compounds 25, 29, and 31 were the most active hLDHA inhibitors. In addition, the inhibitory activities of those nine compounds against the hLDHB isoform were also evaluated, finding that all of them were more selective inhibitors of hLDHA versus hLDHB. Among them, compounds 32 and 34 showed the highest selectivity. Moreover, the most active hLDHA inhibitors (25, 29, 31) were evaluated for their ability to decrease the oxalate production by hyperoxaluric mouse hepatocytes (PH1, PH2 and PH3) in vitro, and the relative oxalate output at 24 h was 16% and 19 % for compounds 25 and 31, respectively, in Hoga1-/- mouse primary hepatocyte cells (a model for PH3). These values improve those of the reference compound used (stiripentol). Compounds 25 and 31 have in common the presence of two hydroxyl groups at rings B and D and an electron-withdrawing group (NO2 or Br) at ring A, pointing to the structural features to be taken into account in future structural optimization., Spanish Ministerio de Ciencia, Innovacion y Universidades - FEDER funds of the European Union RTI2018-098560-B-C21 RTI2018-098560-B-C22, Centro de Instrumentacion Cientifico-Tecnica (CICT) of the University of Jaen, Spain, University of Jaen, Andalusian Consejeria de Economia y Conocimiento (FEDER program 2014-2020) 1380682, European Youth Guarantee contract

Department of Chemistry, University of Allahabad,Allahabad-211 002. Manuscript received 20 December 1976,accepted 22 February, 1977 Synthesis of Biflavans from 6-Hydroxyflavanones.

Contrary to earlier belief, it is shown that the 7-hydroxyl undergoes loss of proton in preference to the 4'-hydroxyl during anhydro-base formation from flavylium salts. This gives an insight into the biogenesis of carajurin (XX) and carajurone (XIX).

The electronic transitions for flavylium cations and quinonoidal bases of 17 substituted flavylium salts have been studied at semiempirical and DFT (density functional theory) levels. Solvent effect on electronic spectra was included by Polarizable Continuum Model, PCM. We assigned longest-wavelength absorption maxima to HOMO -> LUMO transition. Both levels of theory gave good results for electronic transitions of flavylium cations whereas only TDDFT-PCM calculations could be used for electronic transitions of their quinonoidal bases. We also performed absolute pKa calculations of nine flavylium salts at DFT level. The pKa calculated values by our PCM parameterization gave excellent results with mean absolute deviation less than a half of one pKa unit. One-electron reduction potentials were carried out for 5 flavylium cations at DFT level. The theoretical results found were in good agreement with experimental values after adjustment for a systematic deviation. As transições eletrônicas para os cátions flavílio e bases quinonoidais de dezessete sais deste cátion foram estudadas nos níveis semiempírico e DFT (teoria do funcional da densidade). O efeito do solvente nos espectros eletrônicos foi incluído pelo Modelo Contínuo Polarizado, PCM. As transições eletrônicas de menor energia foram assinaladas como transições HOMO -> LUMO. Ambos os níveis de teoria forneceram bons resultados para as transições eletrônicas dos cátions flavílio, enquanto apenas os cálculos por TDDFT-PCM puderam ser empregados para as transições das bases quinonoidais. Foram feitos cálculos de pKa absoluto para nove sais de flavílio em nível DFT. Os valores de pKa calculados pela nossa parametrização do PCM forneceram resultados excelentes, com um desvio médio absoluto de menos de meia unidade de pKa. Foram calculados por DFT potenciais de redução para cinco cátions flavílio. Os resultados teóricos encontrados ficaram em boa concordância com os resultados experimentais após a correção de um desvio sistemático.