Publicação
Flavylium Compounds. From nature’s colour palette to a versatile component in supramolecular devices
| Resumo: | This thesis explores the chemistry of anthocyanins and flavylium-based supramolecular systems, focusing on their structural dynamics, responsiveness to external stimuli, and applications. The first part investigates colour stability in anthocyanins. A comprehensive study of the mono- and di-glycosylated forms of malvidin identifies a pH range where equilibrium is never attained. A novel transient species (B42−) is detected in the diglycosylated malvidin, altering the equilibrium distribution and affecting colour stability. The study of delphinidin 3-O-glucoside with chlorogenic acid reveals a stronger affinity for the coloured forms of the anthocyanin, thus explaining how copigmentation is used to stabilise colour in plants. The second part explores the versatility of flavylium systems beyond colour chemistry. Flavylium compounds complexed with cucurbit[7]uril (CB7) act as photobase generators, capable of modulating the pH of the medium through light stimuli, achieving pH shifts up to ΔpH = 1.5. Quaternary supramolecular complexes are formed through cooperative interactions between CB7, flavylium guests, and a tetracationic cyclophane (blue box), overcoming electrostatic repulsion and resulting in highly fluorescent nanotubular assemblies (Φfl = 0.78). Furthermore, the incorporation of flavylium units in pseudorotaxane axles enables control over the motion of a macrocycle such as CB7 along the thread through light and pH stimuli. In these systems, flavylium acts as a reversible photoswitch, allowing for the development of stimuli-responsive supramolecular materials. By studying anthocyanin chemistry alongside supramolecular chemistry based on the flavylium cation, this thesis demonstrates how molecular interactions govern colour stability, fluorescence, and (supra)molecular dynamics. The results contribute to deepening the understanding of colour stability in anthocyanins while providing supramolecular chemistry with new tools for designing more efficient and functional systems. |
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| Autores principais: | Seco, André Miguel Lopes |
| Assunto: | Supramolecular chemistry Stimuli-responsive materials Anthocyanins Flavylium compounds Cucurbiturils |
| Ano: | 2025 |
| País: | Portugal |
| Tipo de documento: | dissertação de mestrado |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade Nova de Lisboa |
| Idioma: | inglês |
| Origem: | Repositório Institucional da UNL |
| Resumo: | This thesis explores the chemistry of anthocyanins and flavylium-based supramolecular systems, focusing on their structural dynamics, responsiveness to external stimuli, and applications. The first part investigates colour stability in anthocyanins. A comprehensive study of the mono- and di-glycosylated forms of malvidin identifies a pH range where equilibrium is never attained. A novel transient species (B42−) is detected in the diglycosylated malvidin, altering the equilibrium distribution and affecting colour stability. The study of delphinidin 3-O-glucoside with chlorogenic acid reveals a stronger affinity for the coloured forms of the anthocyanin, thus explaining how copigmentation is used to stabilise colour in plants. The second part explores the versatility of flavylium systems beyond colour chemistry. Flavylium compounds complexed with cucurbit[7]uril (CB7) act as photobase generators, capable of modulating the pH of the medium through light stimuli, achieving pH shifts up to ΔpH = 1.5. Quaternary supramolecular complexes are formed through cooperative interactions between CB7, flavylium guests, and a tetracationic cyclophane (blue box), overcoming electrostatic repulsion and resulting in highly fluorescent nanotubular assemblies (Φfl = 0.78). Furthermore, the incorporation of flavylium units in pseudorotaxane axles enables control over the motion of a macrocycle such as CB7 along the thread through light and pH stimuli. In these systems, flavylium acts as a reversible photoswitch, allowing for the development of stimuli-responsive supramolecular materials. By studying anthocyanin chemistry alongside supramolecular chemistry based on the flavylium cation, this thesis demonstrates how molecular interactions govern colour stability, fluorescence, and (supra)molecular dynamics. The results contribute to deepening the understanding of colour stability in anthocyanins while providing supramolecular chemistry with new tools for designing more efficient and functional systems. |
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