Degree: Doctor



Showing 5 latest publications. Total publications: 207
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1. Thermochemistry of amino-1,2,4-triazole derivatives, Amaral, LMPF; Carvalho, TMT; da Silva, MDMCR in JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY, 2024, ISSN: 1388-6150, 
Article in Press,  Indexed in: crossref, scopus, wos  DOI: 10.1007/s10973-024-13161-0 P-010-C6E
Abstract The present work is focused on determining the enthalpy of formation of several derivatives of amino-1,2,4-triazoles. Experimentally, the enthalpies of formation of the crystalline phase and the enthalpies of sublimation of 3-amino- and 3,5-diamino-1H-1,2,4-triazole were derived, respectively, from static-bomb combustion calorimetry and Calvet microcalorimetry or Knudsen effusion measurements. For 4-amino-4H-1,2,4-triazole, only the enthalpy of sublimation was measured. Gas-phase standard molar enthalpies of formation were also estimated using theoretical calculations performed with the G3(MP2) composite approach. The very good agreement of these estimates with the experimental results, support the extension of this study to the estimate of this property for the remaining compounds not studied experimentally. The results obtained are interpreted in terms of structural contributions.

2. Determination and Analysis of Thermodynamic Properties of Methyl Methylanthranilate Isomers, Silva, CAO; Freitas, VLS; da Silva, MDMCR in MOLECULES, 2023, ISSN: 1420-3049,  Volume: 28, 
Article,  Indexed in: crossref, scopus, wos  DOI: 10.3390/molecules28186686 P-00Z-21V
Abstract The enthalpies of formation in the gaseous phase of methyl 3-methylanthranilate and methyl 5-methylanthranilate were determined from experimental measurements of the corresponding standard energies of combustion, obtained from combustion calorimetry, and the standard enthalpies of vaporization and sublimation, obtained from Calvet microcalorimetry and Knudsen mass-loss effusion. A computational study, using the G3(MP2)//B3LYP composite method, has also been performed for the calculation of the gas-phase standard enthalpies of formation of those two molecules at T = 298.15 K, as well as for the remaining isomers, methyl 4-methylanthranilate and methyl 6-methylanthranilate. The results have been used to evaluate and analyze the energetic effect of the methyl substituent in different positions of the ring.

3. Thermal Study of Two Benzotriazole Derivatives, Lima, ACMO; Silva, ALR da Silva, MDMCR in U.Porto Journal of Engineering, 2022, ISSN: 2183-6493,  Volume: 8, 
Article,  Indexed in: crossref, scopus  DOI: 10.24840/2183-6493_008.002_0014 P-00W-GZT
Abstract An experimental study based on the thermal analysis of 5-methyl-1H-benzotriazole and 5,6-dimethyl-1H-benzotriazole was developed, by using differential scanning calorimetry. Additionally, a summary of the experimental techniques and computational methodology being performed, in order to complement the energetic study of both compounds, is described. The knowledge of the thermochemical, thermophysical and structural properties of functionalized benzotriazoles is relevant for the evaluation of their chemical behaviour, as well as in the prediction of the reactivity of similar compounds that have not been thermodynamically characterized. © 2022, Universidade do Porto - Faculdade de Engenharia. All rights reserved.

4. Thermodynamic properties of 2-mercapto-, 2,5-dimethyl- and 2-mercapto-5-methyl-1,3,4-thiadiazole, Silva, ALR Goncalves, JM; Morais, VMF; da Silva, MDMCR in JOURNAL OF CHEMICAL THERMODYNAMICS, 2022, ISSN: 0021-9614,  Volume: 165, 
Article,  Indexed in: crossref, scopus, wos  DOI: 10.1016/j.jct.2021.106644 P-00V-JHR
Abstract The focus of this work is the establishment of energetic-structural correlations of compounds containing a pentagonal heterocyclic ring with different substituents, and consequent contribution on the assessment of their thermodynamic stability and a thorough insight on the thiol-thione tautomeric equilibrium. In this work we report an experimental and computational thermochemical study of three mercaptothiadiazoles: 2-mercapto-1,3,4-thiadiazole, 2-mercapto-5-methyl-1,3,4-thiadiazole and 2,5-dimethyl1,3,4-thiadiazole. The experimental data were determined mainly from calorimetric techniques and from effusion method. Thermochemical properties such as the enthalpies of formation, both in crystalline and gaseous phases, the enthalpies of fusion and of sublimation of each compound, as well as the Gibbs energies of formation were derived. Thus, the methyl-substituted thiadiazole is the more stable species in both gaseous and crystalline phases. In addition, quantum chemical calculations were carried out for those isolated molecules. This approach confirms the thione form as the predominant tautomer for the mercaptothiadiazoles. Finally, the activation energies of the tautomeric equilibrium of the mercaptothiadiazoles were calculated in the gas-phase, aqueous and dimethylsulfoxide solutions, showing that the thiol ? thione single hydrogen transfers are quite unfavourable reactions in gas phase and in a presence of polar solvents. (c) 2021 Elsevier Ltd.

5. Metal-ligand binding energies in copper (II) and nickel (II) complexes with tetradentate N2O2 Schiff base ligands, Silva, ALR Oliveira, PCFC; Goncalves, JM; Morais, VMF; da Silva, MDMCR in INORGANICA CHIMICA ACTA, 2022, ISSN: 0020-1693,  Volume: 535, 
Article,  Indexed in: crossref, scopus, wos  DOI: 10.1016/j.ica.2022.120845 P-00W-1HE
Abstract This work constitutes a new contribution for understanding the relationship between the metal-ligand bonding and, indirectly, the inherent reactivity of metallic complexes with tetradentate N2O2 Schiff base ligands, being reported the energetic characterization of two transition metal complexes - (N,AT c -bis(salicylaldehydo)tetramethylenediiminate)nickel(II) and (N,N' -bis(salicylaldehydo)propylenediiminate)copper(II). The standard molar enthalpies of formation of these complexes were determined by solution-reaction calorimetry measurements. Their standard molar enthalpies of sublimation, at T = 298.15 K, were obtained by an effusion method. From these studies, the gas-phase enthalpies of formation of Ni(II) and Cu(II) complexes, at T = 298.15 K, were derived. Differences between the metal-ligand and mean hydrogen-ligand bond dissociation enthalpies were derived and discussed in structural terms, in comparison with identical parameters for complexes of the same metals with analogous tetradentate Schiff bases. High-level quantum chemical calculations have also been conducted, complementing the results obtained experimentally.