Degree: Doctor

Affiliation(s):

CIQUP - FCUP

Bio

Vera Freitas is a researcher and professor in the field of Physical Chemistry. She obtained her PhD in Thermochemistry from Porto University, Portugal, in 2011. After completing her PhD, she conducted a scientific project in Thermochemistry under a post-doctoral grant for seven years at the Chemistry Research Center of the University of Porto (CIQUP). She currently holds a research position at CIQUP & The Institute of Molecular Sciences Research Center within the Department of Chemistry and Biochemistry at the University of Porto.

At the research center, she is a key member of the Molecular Thermodynamics for Sustainability research group. Her work primarily involves experimental (thermochemical and thermophysical) and computational studies of organic compounds, with a particular emphasis on those relevant to the pharmaceutical industry and the development of sustainable new materials.

In addition to her research, she actively participates in teaching courses focused on molecular energetics, leveraging her extensive expertise in thermodynamics to enhance the education and training of students in this field.

Projects
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Publications
Showing 5 latest publications. Total publications: 55
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1. Thermodynamic study of tin tetraiodide (SnI4) 4 ) sublimation by effusion techniques, Romagnoli, L; Almeida, ARRP; Ferraz, JMS; Latini, A; Freitas, VLS da Silva, MDMCR Schiavi, PG; Ciprioti, SV; Ciccioli, A in JOURNAL OF CHEMICAL THERMODYNAMICS, 2024, ISSN: 0021-9614,  Volume: 199, 
Article,  Indexed in: crossref, scopus, unpaywall, wos  DOI: 10.1016/j.jct.2024.107348 P-011-0HK
Abstract This study presents the first investigation of the sublimation behavior of tin tetraiodide, SnI4, 4 , using effusion- based techniques, within a low temperature range (313-340) K. The temperature range covered in the experiments was lower than in previously reported studies based on static methods. Knudsen Effusion Mass Loss (KEML) measurements were performed in the range of (317.1-339.6) K using effusion cells with different orifice sizes. The vapor pressures were measured in the range (0.13-1.13) Pa and were found to be independent of the orifice size. The standard molar enthalpy and Gibbs energy of sublimation at 298.15 K obtained by the Clarke and Glew fit of experimental data are (88.1 +/- 0.9) kJ & sdot;mol-1 & sdot; mol- 1 and (38.96 +/- 0.08) kJ & sdot;mol-1, & sdot; mol- 1 , respectively. Knudsen Effusion Mass Spectrometry (KEMS) experiments were also performed in the range (313.3-331.7) K, resulting in a sublimation enthalpy value in good agreement with the KEML values and not negligibly higher vapor pressure values. KEMS vapor pressure data were also analyzed by the third-law method. A comparison of our experimental results with the literature data available for both sublimation and evaporation properties of SnI4 4 is reported. Additionally, ancillary DFT and ab initio calculations were performed to estimate the molecular properties of SnI4(g) 4 (g) and the extent of the gas-phase dissociation to SnI2 2 and I2. 2 .

2. 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.

3. 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.

4. Thermochemical study of anthranilate derivatives: Effect of the size of the alkyl substituent, Freitas, VLS Silva, CAO; da Silva, MDMCR in JOURNAL OF CHEMICAL THERMODYNAMICS, 2021, ISSN: 0021-9614,  Volume: 158, 
Article,  Indexed in: crossref, scopus, wos  DOI: 10.1016/j.jct.2021.106441 P-00T-N9Z
Abstract The gas-phase enthalpies of formation of two fragrance compounds, methyl anthranilate and butyl anthranilate, at T = 298.15 K, were determined from the combination of the corresponding enthalpies of vaporisation and energies of combustion, obtained from Calvet microcalorimetry and combustion calorimetry measurements, respectively. Additionally, theoretical calculations were performed, using the G3(MP2)//B3LYP composite method, to estimate the gas-phase enthalpies of formation of the two fragrance compounds. The good agreement between the experimental and computational gas-phase enthalpies of formation of the methyl anthranilate and butyl anthranilate, provided the confidence for extending the theoretical study to propyl anthranilate. Furthermore, the results were interpreted in terms of enthalpic increments, aiming to evaluate and understand the energetic effect inherent to the alkyl group (methyl, ethyl, propyl or butyl) present in the ester functional group of the anthranilate derivatives. (c) 2021 Elsevier Ltd.

5. The Relative Thermodynamic Stability of Diamond and Graphite, White, MA; Kahwaji, S; Freitas, VLS Siewert, R; Weatherby, JA; da Silva, MDMCR Verevkin, SP; Johnson, ER; Zwanziger, JW in ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, 2021, ISSN: 1433-7851,  Volume: 60, 
Article,  Indexed in: crossref, scopus, wos  DOI: 10.1002/anie.202009897 P-00S-ZNF
Abstract Recent density-functional theory (DFT) calculations raised the possibility that diamond could be degenerate with graphite at very low temperatures. Through high-accuracy calorimetric experiments closing gaps in available data, we reinvestigate the relative thermodynamic stability of diamond and graphite. For T400 K, graphite is always more stable than diamond at ambient pressure. At low temperatures, the stability is enthalpically driven, and entropy terms add to the stability at higher temperatures. We also carried out DFT calculations: B86bPBE-25X-XDM//B86bPBE-XDM and PBE0-XDM//PBE-XDM results overlap with the experimental -T Delta S results and bracket the experimental values of Delta H and Delta G, displaced by only about 2x the experimental uncertainty. Revised values of the standard thermodynamic functions for diamond are Delta H-f(o)=-2150 +/- 150 J mol(-1), Delta S-f(o)=3.44 +/- 0.03 J K-1 mol(-1) and Delta(f)G(o)=-3170 +/- 150 J mol(-1).