Degree: Doctor

Affiliation(s):

FCUP

Publications
Showing 5 latest publications. Total publications: 209
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1. 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.

2. 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.

3. Experimental and Theoretical Investigation on the Thermochemistry of 3-Methyl-2-benzoxazolinone and 6-Nitro-2-benzoxazolinone, Silva, ALR Costa, VMS; da Silva, MDMCR in MOLECULES, 2022, Volume: 27, 
Article,  Indexed in: crossref, scopus, wos  DOI: 10.3390/molecules27010024 P-00V-W39
Abstract The determination of the reliable thermodynamic properties of 2-benzoxazolinone derivatives is the main goal of this work. Some correlations are established between the energetic properties determined and the structural characteristics of the title compounds, and the reactivity of this class of compounds is also evaluated. Static-bomb combustion calorimetry and high-temperature Calvet microcalorimetry were used to determine, respectively, the standard molar enthalpies of formation in the solid state and the standard molar enthalpies of sublimation, both at T = 298.15 K. Using the results obtained for each compound, the respective gas-phase standard molar enthalpy of formation was derived. High-level quantum chemical calculations were performed to estimate the same property and the results evidence good accordance. Moreover, the gas-phase relative thermodynamic stability of 2-benzoxazolinone derivatives was also evaluated using the respective gas-phase standard molar Gibbs energy of formation. In addition, the relationship between the energetic and structural characteristics of the benzoxazolinones is presented, evidencing the enthalpic increments associated with the presence of a methyl and a nitro groups in the molecule, and this effect is compared with similar ones in other structurally related compounds.

4. A Promising Thermodynamic Study of Hole Transport Materials to Develop Solar Cells: 1,3-Bis(N-carbazolyl)benzene and 1,4-Bis(diphenylamino)benzene, Mentado Morales, J; Ximello Hernandez, A; Salinas Luna, J; Freitas, VLS da Silva, MDMCR in MOLECULES, 2022, Volume: 27, 
Article,  Indexed in: crossref, scopus, wos  DOI: 10.3390/molecules27020381 P-00V-XEX
Abstract The thermochemical study of the 1,3-bis(N-carbazolyl)benzene (NCB) and 1,4-bis(diphenylamino)benzene (DAB) involved the combination of combustion calorimetric (CC) and thermogravimetric techniques. The molar heat capacities over the temperature range of (274.15 to 332.15) K, as well as the melting temperatures and enthalpies of fusion were measured for both compounds by differential scanning calorimetry (DSC). The standard molar enthalpies of formation in the crystalline phase were calculated from the values of combustion energy, which in turn were measured using a semi-micro combustion calorimeter. From the thermogravimetric analysis (TGA), the rate of mass loss as a function of the temperature was measured, which was then correlated with Langmuir's equation to derive the vaporization enthalpies for both compounds. From the combination of experimental thermodynamic parameters, it was possible to derive the enthalpy of formation in the gaseous state of each of the title compounds. This parameter was also estimated from computational studies using the G3MP2B3 composite method. To prove the identity of the compounds, the H-1 and C-13 spectra were determined by nuclear magnetic resonance (NMR), and the Raman spectra of the study compounds of this work were obtained.

5. Thermochemical study to assess the energetical and structural effects of nitro substituents in methyl benzoate isomers, Ledo, JM; Flores, H; Ramos, F; Freitas, VLS da Silva, MDMCR in JOURNAL OF CHEMICAL THERMODYNAMICS, 2022, ISSN: 0021-9614,  Volume: 173, 
Article,  Indexed in: crossref, scopus, wos  DOI: 10.1016/j.jct.2022.106837 P-00W-PP6
Abstract Combined experimental and computational studies were performed aiming the analysis of energetic properties vs structural characteristics of three methyl nitrobenzoate isomers (methyl 2-nitrobenzoate, M2NB, methyl 3-nitro benzoate, M3NB, methyl 4-nitrobenzoate, M4NB). The experimental studies include the determination of the enthalpy of formation in the condensed state (crystal and liquid) of the compounds by static combustion, and the determination of enthalpies of phase transition, using Differential Scanning Calorimetry, high temperature Calvet microcalorimetry and the Knudsen effusion method. These data were combined to derive the enthalpy of formation of the methyl nitrobenzoate isomers in the gaseous phase, at T = 298.15 K. At the computational level, the gas-phase enthalpy of formation of the methyl nitrobenzoate isomers were estimated using theoretical approaches, resorting to the G3(MP2)//B3LYP composite method and to appropriate hypothetical gas-phase reactions. The enthalpies of formation obtained experimental and computationally will be discussed and the energetic structural synergies for the three methyl nitrobenzoate, along with other analogous isomers, will be also analyzed.