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Stenhouse photoswitches as new materials for smart applications
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Moléculas fotocrómicas têm vindo a ser cada vez mais estudadas devido à possibilidade de variação de algumas propriedades físicas com a aplicação da luz. Embora exista uma diversidade de moléculas fotocrómicas já descritas na literatura, recentemente uma nova classe de moléculas começou a ser investigada. Essa nova classe são os Donor-Acceptor Stenhouse Adducts (DASA). Os DASA, além de responderem a dois tipos de estímulos, a radiação e a temperatura, a radiação em causa é de baixa energia, o que providencia uma maior variedade de aplicações, nomeadamente em ciências dos materiais e biológicas. A síntese dos DASA inicia-se a partir do furfural, um composto que pode ser obtido a partir de resíduos da biomassa, que por condensação de Knoevenagel com um dicarboxilato, formando o precursor do DASA. A síntese dos DASA fica completa depois da adição de uma amina secundária. Esta reação é feita maioritariamente usando água como solvente e à temperatura ambiente sendo uma vantagem na perspetiva de química mais sustentável. O equilíbrio entre os dois isómeros deste tipo de moléculas está dependente do tipo de solvente utilizado. Desta forma, existe um grande potencial na utilização de solventes alternativos tais como Líquidos Iónicos (ILs) ou Solventes Eutéticos (DES), uma vez que poderão deslocar o equilíbrio de maneira diferente dos solventes orgânicos tradicionais. No contexto dos ILs, os líquidos iónicos magnéticos (MILs) apresentam vantagens adicionais, uma vez que as suas propriedades dependem do campo magnético aplicado, aumentando assim o leque de aplicações para esta classe de moléculas. Nesta dissertação foi desenvolvido uma nova classe de DASA-MIL que se baseia na síntese de MILs tendo na sua estrutura a molécula de DASA. Estes tipos de moléculas poderão responder a três estímulos diferentes: luz, temperatura e campo magnético.
Photochromic molecules have been widely studied due to the possibility to change their physical properties with an external stimulus. There are several photochromic molecules already reported in the literature, although a new type has been recently discovered by Alaniz et al., that are the Donor-Acceptor Stenhouse Adducts (DASA). The synthesis of DASA starts with furfural, a known derived biomass waste. By Knoevenagel condensation with a dicarboxylate it forms the precursor of DASA, and finally by addition of a secondary amine the DASA is formed. This reaction, occurs mainly in water and it works at room temperature, being key features for more sustainable chemistry. DASA also have the particularity to respond to two different stimuli (radiation and temperature), requiring a very low energy radiation, which enables a variety of applications, namely material and biological science. The equilibrium of those molecules is solvent dependent thus, there is a great potential on the use of Ionic Liquids (IL) and Deep Eutetic Solvents (DES) as alternative solvents for DASA. Particularly interest have been placed on IL due to the possible combination of Magnetic Ionic Liquids (MILs) with DASA. In this way, it will be possible to apply three different stimuli, namely temperature, light and magnetic field, broadening the number of applications of this type of molecules. In this thesis it was possible to develop a new class of DASA-MIL, that is based on the magnetic ILs synthesis with a DASA moiety on the molecule. In which these molecules are likely to respond to 3 stimuli: light, temperature, and magnetic field.
Photochromic molecules have been widely studied due to the possibility to change their physical properties with an external stimulus. There are several photochromic molecules already reported in the literature, although a new type has been recently discovered by Alaniz et al., that are the Donor-Acceptor Stenhouse Adducts (DASA). The synthesis of DASA starts with furfural, a known derived biomass waste. By Knoevenagel condensation with a dicarboxylate it forms the precursor of DASA, and finally by addition of a secondary amine the DASA is formed. This reaction, occurs mainly in water and it works at room temperature, being key features for more sustainable chemistry. DASA also have the particularity to respond to two different stimuli (radiation and temperature), requiring a very low energy radiation, which enables a variety of applications, namely material and biological science. The equilibrium of those molecules is solvent dependent thus, there is a great potential on the use of Ionic Liquids (IL) and Deep Eutetic Solvents (DES) as alternative solvents for DASA. Particularly interest have been placed on IL due to the possible combination of Magnetic Ionic Liquids (MILs) with DASA. In this way, it will be possible to apply three different stimuli, namely temperature, light and magnetic field, broadening the number of applications of this type of molecules. In this thesis it was possible to develop a new class of DASA-MIL, that is based on the magnetic ILs synthesis with a DASA moiety on the molecule. In which these molecules are likely to respond to 3 stimuli: light, temperature, and magnetic field.
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Photoswitching Donor-Acceptor Stenhouse Adducts (DASA) Ionic liquids Deep Eutetic Solvents (DES)