Browsing by Author "Melle-Franco, Manuel"
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- Using COSMO-RS to design choline chloride pharmaceutical eutectic solventsPublication . Abranches, Dinis O.; Larriba, Marcos; Silva, Liliana P.; Melle-Franco, Manuel; Palomar, José F.; Pinho, Simão; Coutinho, João A.P.Deep eutectic solvents (DES) present interesting properties, mostly connected to their solvation ability, and have been subject to much research in the recent past. Currently, the discovery of new eutectic solvents is accomplished by experimentally measuring the eutectic point of random systems, often using choline chloride as a hydrogen bond acceptor. In this work, the eutectic temperatures of new choline chloride-based eutectic systems were experimentally assessed. These data, along with other previously reported in the literature, were used to evaluate a method based on COSMO-RS to predict the eutectic temperature of choline-chloride based mixtures. The predictive methodology herein developed allows for the quick scanning of a large matrix of systems in order to identify those more promising to be in the liquid state at a given temperature. To validate this method, the eutectic temperature of pharmaceutical drug mixtures was predicted and, then, assessed experimentally, showing that COSMO-RS is useful in the design of liquid drug-based formulations.
- What a difference a methyl group makes-probing choline-urea molecular interactions through urea structure modificationPublication . Silva, Liliana P.; Araújo, Catarina; Abranches, Dinis O.; Melle-Franco, Manuel; Martins, Mónia A.R.; Nolasco, Mariela M.; Ribeiro-Claro, Paulo J.A.; Pinho, Simão; Coutinho, João A.P.There is a lack of fundamental knowledge on deep eutectic solvents, even for the most extensively studied mixtures, such as the mixture of cholinium chloride and urea, which prevents a judicious choice of components to prepare new solvents. The objective of this work is to study and understand the fundamental interactions between cholinium chloride and urea that lead to the experimentally observed melting temperature depression. To do so, the structure of urea was strategically and progressively modified, in order to block certain interaction centres, and the solid–liquid equilibrium data of each new binary system was experimentally measured. Using this approach, it was concluded that the most important interaction between cholinium chloride and urea occurs through hydrogen bonding between the chloride anion and the amine groups. Any blockage of these groups severely hampers the melting point depression effect. Raman spectroscopy and DFT calculations were utilized to study in more detail this hydrogen bonding and its nuances.