Rodrigo De Paula - Academia.edu (original) (raw)
Papers by Rodrigo De Paula
Catalysis Communications, 2008
The catalytic efficiency of the chloro [5,10,15,20-(1,3-dimethylimidazolium-2-yl)porphyrinatomang... more The catalytic efficiency of the chloro [5,10,15,20-(1,3-dimethylimidazolium-2-yl)porphyrinatomanganese(III)] tetraiodide is evaluated in the epoxidation of olefins under homogeneous conditions, using hydrogen peroxide as oxidant. The catalytic behaviour of this metalloporphyrin is strongly dependent on the co-catalyst used; high conversions are found for all olefins studied, affording the corresponding epoxides as the major products.
Química Nova
The experimental activities for undergraduate chemistry students play an important role to develo... more The experimental activities for undergraduate chemistry students play an important role to develop skills and expertise in that science thus, the practice-experimental classes are so important to achieve this purpose. This work deals with a demonstrative experience for dye separation from food coloring sample using liquid column chromatography. Beyond the experimental practice and the facility in visualizing the separation, this demonstration shows how a simple experiment involving alternative and easy access materials can promote a meaningful learning once it is possible to handle the acquired data, trace and analyze the results themselves, thus developing skills rather than the operational procedure. This proposal could be implemented in initial chemistry classes in Brazilian universities. Sea and river sands were used as stationary phases and aqueous ethanolic solutions were used as mobile phases. A food coloring (a mixture of 3 dyes) was chosen as sample to be studied. Chromatog...
An imidazolium tetrasubstituted cationic porphyrin derivative (the free base and its Zn(II) compl... more An imidazolium tetrasubstituted cationic porphyrin derivative (the free base and its Zn(II) complex) with five-membered heterocyclic groups in the meso-positions were synthesized using microwave irradiation, and the compounds obtained characterized by 1 H-NMR and mass spectrometry. We observed that under microwave irradiation the yield is similar to when the synthesis is performed under conventional heating, however, the time required to prepare the porphyrins decreases enormously. In order to investigate the electronic state of these compounds, we employed UV-Vis and fluorescence spectroscopy combined with quantum chemical calculations. The results reveal the presence, in both compounds, of a large number of electronic states involving the association between the Soret and a blue-shifted band. The Soret band in both compounds also shows a considerable solvent dependence. As for emission, these compounds present low quantum
Química Nova, 2018
An undergraduate organic chemistry experiment for oil extraction and biodiesel production using a... more An undergraduate organic chemistry experiment for oil extraction and biodiesel production using alternative biomass was developed, whereby oils of avocado, coconut and spent coffee grounds were obtained and submitted to transesterification reaction with CH 3 OH under NaOH catalysis. Avocado and coffee oils were obtained by typical extraction and coconut oil was obtained through water evaporation of coconut milk in a domestic microwave oven. The commercial oil of licuri (Syagrus coronate), a Brazilian native biomass, was also converted to biodiesel. All four oils and four biodiesels were characterized by 1 H-NMR and FTIR, and a comparative study of these spectra reveled that FTIR analyses alone provides enough information to discriminate between oil and biodiesel and confirm transesterification reaction. Besides, the unsaturation degree of all oils was determined by 1 H-NMR. A mechanistic proposal concerning the role of NaOH catalysis is presented, excluding the sodium methoxide formation.
Lista de Abreviaturas BHT-composto químico utilizado correntemente como supressor de radicais cen... more Lista de Abreviaturas BHT-composto químico utilizado correntemente como supressor de radicais centrados no átomo de oxigénio. Vulgarmente é conhecido por t-butil-hidroxitolueno (do inglês, butylated hydroxytoluene); porém, o nome sugerido pela IUPAC é 2,6-di-t-butil-4metilfenol. t-BuOOH-hidroperóxido de t-butilo CICECO-Centro de Investigação em Materiais Cerâmicos e Compósitos m-CPBA-ácido meta-cloroperbenzoico ddupleto ddduplo dupleto DFT-Teoria Funcional da Densidade (do inglês, Density Fuctional Theory) equiv.-equivalente molar ESI-MSionização por "Electrospray" em espectrometria de massa (do inglês, Electrospray Ionization-Mass Spectrometry) ε ε ε ε-coeficiente de absortividade molar (em dm 3 .mol-1 .cm-1) FT-IRespectroscopia de infravermelho com transformadas de Fourier (do inglês, Fourier Transform-InfraRed) GC-FIDcromatrógrafo de gás acoplado a um detector do tipo FID (do inglês, Gas Chromatography Flame Ionization Detector) GC-MS-cromatógrafo de gás acoplado a um detector do tipo MS (do inglês, Gas Chromatography Mass Spectrometer) H 2-1DCP3DMImP-(2,6-diclorofenil),10,15,20-tris(1,3-dimetilimidazolínio-2-il)porfirina
An undergraduate organic chemistry experiment for oil extraction and biodiesel production using a... more An undergraduate organic chemistry experiment for oil extraction and biodiesel production using alternative biomass was developed, whereby oils of avocado, coconut and spent coffee grounds were obtained and submitted to transesterification reaction with CH3OH under NaOH catalysis. Avocado and coffee oils were obtained by typical extraction and coconut oil was obtained through water evaporation of coconut milk in a domestic microwave oven. The commercial oil of licuri (Syagrus coronate), a Brazilian native biomass, was also converted to biodiesel. All four oils and four biodiesels were characterized by 1H-NMR and FTIR, and a comparative study of these spectra reveled that FTIR analyses alone provides enough information to discriminate between oil and biodiesel and confirm transesterification reaction. Besides, the unsaturation degree of all oils was determined by 1H-NMR. A mechanistic proposal concerning the role of NaOH catalysis is presented, excluding the sodium methoxide formation.
Photochemical & Photobiological Sciences, 2004
The photophysics of 3-(benzoxazol-2-yl)-7-(N,N-diethylamino)chromen-2-one was studied in differen... more The photophysics of 3-(benzoxazol-2-yl)-7-(N,N-diethylamino)chromen-2-one was studied in different solvents and in SDS micelles. This compound presents characteristics which include an S(0)---> S(1) ( pi,pi*) transition with a (1)(n,pi*) perturbative component, due to the electronic coupling between the diethylamino group and the coumarin ring, considerable solvatochromism, dual fluorescence and high fluorescence quantum yields in almost all solvents studied. The electronic structure of the S(1) and S(2) excited states permits vibronic coupling between them, making configurational changes of the S(2) excited state possible, leading to the formation of an S(2)(TICT) state. Analysis of the TCSPC data indicates an equilibrium between the S(2)(TICT) and S(1)(LE) states in favour of the former. In protic solvents, the hydrogen bonding between the solvent and the diethylamino moiety results in the formation of an S(2)(HICT) state, making internal conversion an important deactivation process. Quantum mechanical calculations for the isolated molecule show that the diethylamino group in the S(2)(TICT) state is twisted at least 56 degree from the plane of the coumarin ring, with partial electronic decoupling between -NEt(2) and the coumarin ring. This twisting angle must be positively influenced by solute-solvent interactions. [capital Phi](ST) is found to be small, but not negligible. However, Phi (delta) can be considered negligible, an indication that T(1) is a short-lived state. Based on the experimental data and theoretical calculations, the most probable sequence for the first excited states, including the TICT state, is T(1)(n, pi*) < S(2)(TICT) < S(1)(pi,pi*) approximate S(2) (n,pi*).
Journal of Porphyrins and Phthalocyanines, 2009
Cheap and abundant natural products can be transformed into products of higher commercial value. ... more Cheap and abundant natural products can be transformed into products of higher commercial value. One of the approaches for the functionalization of organic compounds is their oxidation in the presence of an oxygen atom donor, under the influence of a suitable catalyst. Metalloporphyrins, with structures based on the well known meso-tetraphenylporphyrin (TPPH2), are amongst the catalysts commonly studied and have demonstrated to be efficient in the oxygenation of organic compounds. These transformations have been studied in the presence of different oxygen atom donors. However, our biomimetic oxidative approach is based on the use of clean and environmentally benign hydrogen peroxide in the presence of metalloporphyrins. This approach will be outlined in this review.
Journal of Photochemistry and Photobiology A: Chemistry, 2008
The solvatochromism and other spectroscopic and photophysical characteristics of four azo dispers... more The solvatochromism and other spectroscopic and photophysical characteristics of four azo disperse dyes, derived from 2-amino-5-nitrothiazole, were evaluated and interpreted with the aid of experimental data and quantum mechanical calculations. For the non-substituted compound two conformers, E and Z, were proposed for the isolated molecules, being the second one considerably less stable. The optimization of these structures in combination with
Química Nova, 2021
OXYGEN IN THE COVID-19 CONTEXT: WHAT WE KNOW ABOUT THE MOLECULE WE BREATHE AND THE CENTRAL ROLE O... more OXYGEN IN THE COVID-19 CONTEXT: WHAT WE KNOW ABOUT THE MOLECULE WE BREATHE AND THE CENTRAL ROLE OF CHEMISTRY. In this work, the role of chemistry in the coronavirus disease 2019 (COVID-19) pandemic is highlighted through the medical oxygen supply crises in Brazil, as an example of oxygen utility in health. Starting from oxygen chemical characterization, the oxygen cycle in nature is discussed to show how oxygen is formed through photosynthesis, followed by the description of the industrial oxygen production from atmospheric air, including physical-chemical aspects. The use of medical oxygen concentrator is presented and how this device works from the chemical point of view. Besides, the noninvasive and painless oximetry is described in terms of how oxygen saturation level in blood is measured using LED - light emitting diode.
RSC Advances
P450-bioinspired Jacobsen/Cell(NEt2) catalysts have been applied in RhB dye oxidation, which is u... more P450-bioinspired Jacobsen/Cell(NEt2) catalysts have been applied in RhB dye oxidation, which is used illegally in food industries of some countries.
Journal of Heterocyclic Chemistry, Mar 1, 2008
Page 1. Mar-Apr 2008 Kinetic Study of meso-Tetraphenylporphyrin Synthesis Under Microwave Irradia... more Page 1. Mar-Apr 2008 Kinetic Study of meso-Tetraphenylporphyrin Synthesis Under Microwave Irradiation 453 Rodrigo De Paula, Maria AF Faustino, Diana CGA Pinto, Maria GPMS Neves, José AS Cavaleiro* University of Aveiro, Department of Chemistry, Campus Santiago. ...
Journal of Molecular Catalysis A: Chemical, 2015
ABSTRACT A new catalytic system based on an immobilized imidazolyl manganese porphyrin for the ox... more ABSTRACT A new catalytic system based on an immobilized imidazolyl manganese porphyrin for the oxidation of olefins is presented. Merrifield resin (MR) and functionalized silica gel (SG) were chosen as supports. The results indicate that the MR system shows high reaction rates, high efficiency with hydrogen peroxide as oxidant and good recyclability up to four times, without a dramatic loss in the catalytic efficiency. The catalytic behavior seems to be strongly influenced by the immobilization reaction conditions. The oxidation reactions performed for cis-cyclooctene, styrene, cyclohexene and geraniol give the corresponding epoxides, with very high selectivity, when the MR system is used. Some considerations concerning the high efficiency of the MR system are put forward.
RSC Advances, 2011
The biomimetic oxidation of lapachol (1) using aqueous hydrogen peroxide as oxidant and chloro[5,... more The biomimetic oxidation of lapachol (1) using aqueous hydrogen peroxide as oxidant and chloro[5,10,15,20-tetrakis(2,6-dichlorophenyl)porphyrinatomanganese(III)] (Mn-Porph) as catalyst is described. A comparison between the obtained results and those described for the oxidation of lapachol using meta-chloroperoxybenzoic acid (m-CPBA) reveals, besides different reaction products, a completely different selectivity. Unlike the m-CPBA approach, where ortho-naphthoquinones are obtained, paranaphthoquinones are highly favoured when using Mn-Porph and H 2 O 2. Moreover, a new lactone is isolated and characterized in the present work.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2013
The steady state and time resolved experiments together with absorption and emission spectroscopi... more The steady state and time resolved experiments together with absorption and emission spectroscopies and quantum chemical calculations have been employed to investigate spectroscopic properties of a xanthone-type compound (ethyl 3,12-dioxopyran[3,2-a]xanthone-2-carboxylate). The spectroscopic data show good agreement with results obtained from quantum chemical calculations. Additionally, this compound shows expressive quantum efficiency for triplet population and a quantum efficiency of singlet oxygen generation very close to unity. Correlations between the nature of singlet and triplet excited states and spectroscopic properties were performed in order to understand the high quantum efficiency of singlet oxygen generation by this compound.
Journal of Photochemistry and Photobiology A: Chemistry, 2004
It was shown that 3-benzoxazol-2-yl-7-(N,N-diethylamino)-chromen-2-one is suitable to perform as ... more It was shown that 3-benzoxazol-2-yl-7-(N,N-diethylamino)-chromen-2-one is suitable to perform as a fluorescent probe, to analyse physical parameters related to organised systems. Micropolarity, microviscosity, critical aggregation and micelle concentration data, in SDS and CTAB micelles, using the proposed compound as fluorescent probe show the compound is allocated, in both micelles, in a strongly polar hydrophilic region (the parameter E T (30) is equal to 61.3 and 61.9 kcal/mol, respectively, in SDS and CTAB micelles, whereas Lippert's f parameter is equal to 0.35). The CMC of SDS in pure water (7.5 × 10 −3 mol/dm 3) agrees with the reported values. For SDS and CTAB micelles in buffered medium (PBS buffer, pH 7.4, NaCl 0.9%, w/w), the estimated critical aggregation concentrations (4.6 × 10 −3 and 9.2 × 10 −4 mol/dm 3 , respectively, for SDS and CTAB) also agree with the results obtained using equivalent conditions.
Journal of Molecular Catalysis A: Chemical, 2011
The oxidation of styrene and derivatives with H 2 O 2 catalyzed by manganese porphyrins in aceton... more The oxidation of styrene and derivatives with H 2 O 2 catalyzed by manganese porphyrins in acetonitrile is described. The effect of the imidazolium substituent on the catalytic efficiency has been also considered. The thermodynamic analysis has indicated that enthalpy rules styrene oxidation when catalysts Mn(Porph)-1 and Mn(Porph)-2 are used whereas the entropy is the driven force for Mn(Porph)-3 and Mn(Porph)-4 catalyzed reactions. Interestingly, an enthalpy-entropy compensation phenomenon is observed when comparing the thermodynamic results obtained for catalysts Mn(Porph)-3 and Mn(Porph)-4. Hammett plots for the studied manganese porphyrins provided small-values, and this is typical for multi-step reactions, indicating that there is no significant charge separation in the transition state. For Mn(Porph)-1 and Mn(Porph)-2 the formation of multiple active species can be put forward whereas for Mn(Porph)-3 and Mn(Porph)-4 a concerted-type mechanism, via metalloxetane intermediate, fits well with the values obtained for those catalysts. The imidazolium-based catalysts have shown to be efficient catalysts in styrene and derivatives oxidation with hydrogen peroxide.
Journal of Mass Spectrometry, 2014
Electrospray ionization mass spectrometry/mass spectrometry in the positive ion mode was used to ... more Electrospray ionization mass spectrometry/mass spectrometry in the positive ion mode was used to investigate the gas-phase chemistry of multicharged ions from solutions of porphyrins with 1,3-dimethylimidazolium-2-yl (DMIM) and 1-methylimidazol-2-yl (MIm) meso-substituents. The studied compounds include two free bases and 12 complexes with transition metals (Cu(II), Zn(II), Mn(III), and Fe(III)). The observed multicharged ions are either preformed or formed during the electrospraying process by reduction or protonation and comprise closed-shell and hypervalent mono-radical and bi-radical ions. The observed extensive and abundant fragmentation of the DMIM and MIm meso-substituents is a characteristic feature of these porphyrins. Fragments with the same mass values can be lost from the meso-substituents either as charged or neutral species and from closed-shell and hypervalent radical ions. Reduction processes are observed for both the free bases and the metallated DMIM porphyrins and occur predominantly by formation of hypervalent radicals that fragment, at low energy collisions, by loss of methyl radicals with formation of the corresponding MIm functionalities. These findings confirm that, when using electrospray ionization, reduction is an important characteristic of cationic meso-substituted tetrapyrrolic macrocycles, always occurring when delocalization of the formed hypervalent radicals is possible. For the Fe(III) and Mn(III) complexes, reduction of the metal centers is also observed as the predominant fragmentation of the corresponding reduced ions through losses of charged fragments testifies. The fragmentation of the closed-shell ions formed by protonation of the MIm porphyrins mirrors the fragmentation of the closed-shell ions of their DMIM counterparts.
Journal of Heterocyclic Chemistry, 2008
Page 1. Mar-Apr 2008 Kinetic Study of meso-Tetraphenylporphyrin Synthesis Under Microwave Irradia... more Page 1. Mar-Apr 2008 Kinetic Study of meso-Tetraphenylporphyrin Synthesis Under Microwave Irradiation 453 Rodrigo De Paula, Maria AF Faustino, Diana CGA Pinto, Maria GPMS Neves, José AS Cavaleiro* University of Aveiro, Department of Chemistry, Campus Santiago. ...
Catalysis Communications, 2008
The catalytic efficiency of the chloro [5,10,15,20-(1,3-dimethylimidazolium-2-yl)porphyrinatomang... more The catalytic efficiency of the chloro [5,10,15,20-(1,3-dimethylimidazolium-2-yl)porphyrinatomanganese(III)] tetraiodide is evaluated in the epoxidation of olefins under homogeneous conditions, using hydrogen peroxide as oxidant. The catalytic behaviour of this metalloporphyrin is strongly dependent on the co-catalyst used; high conversions are found for all olefins studied, affording the corresponding epoxides as the major products.
Química Nova
The experimental activities for undergraduate chemistry students play an important role to develo... more The experimental activities for undergraduate chemistry students play an important role to develop skills and expertise in that science thus, the practice-experimental classes are so important to achieve this purpose. This work deals with a demonstrative experience for dye separation from food coloring sample using liquid column chromatography. Beyond the experimental practice and the facility in visualizing the separation, this demonstration shows how a simple experiment involving alternative and easy access materials can promote a meaningful learning once it is possible to handle the acquired data, trace and analyze the results themselves, thus developing skills rather than the operational procedure. This proposal could be implemented in initial chemistry classes in Brazilian universities. Sea and river sands were used as stationary phases and aqueous ethanolic solutions were used as mobile phases. A food coloring (a mixture of 3 dyes) was chosen as sample to be studied. Chromatog...
An imidazolium tetrasubstituted cationic porphyrin derivative (the free base and its Zn(II) compl... more An imidazolium tetrasubstituted cationic porphyrin derivative (the free base and its Zn(II) complex) with five-membered heterocyclic groups in the meso-positions were synthesized using microwave irradiation, and the compounds obtained characterized by 1 H-NMR and mass spectrometry. We observed that under microwave irradiation the yield is similar to when the synthesis is performed under conventional heating, however, the time required to prepare the porphyrins decreases enormously. In order to investigate the electronic state of these compounds, we employed UV-Vis and fluorescence spectroscopy combined with quantum chemical calculations. The results reveal the presence, in both compounds, of a large number of electronic states involving the association between the Soret and a blue-shifted band. The Soret band in both compounds also shows a considerable solvent dependence. As for emission, these compounds present low quantum
Química Nova, 2018
An undergraduate organic chemistry experiment for oil extraction and biodiesel production using a... more An undergraduate organic chemistry experiment for oil extraction and biodiesel production using alternative biomass was developed, whereby oils of avocado, coconut and spent coffee grounds were obtained and submitted to transesterification reaction with CH 3 OH under NaOH catalysis. Avocado and coffee oils were obtained by typical extraction and coconut oil was obtained through water evaporation of coconut milk in a domestic microwave oven. The commercial oil of licuri (Syagrus coronate), a Brazilian native biomass, was also converted to biodiesel. All four oils and four biodiesels were characterized by 1 H-NMR and FTIR, and a comparative study of these spectra reveled that FTIR analyses alone provides enough information to discriminate between oil and biodiesel and confirm transesterification reaction. Besides, the unsaturation degree of all oils was determined by 1 H-NMR. A mechanistic proposal concerning the role of NaOH catalysis is presented, excluding the sodium methoxide formation.
Lista de Abreviaturas BHT-composto químico utilizado correntemente como supressor de radicais cen... more Lista de Abreviaturas BHT-composto químico utilizado correntemente como supressor de radicais centrados no átomo de oxigénio. Vulgarmente é conhecido por t-butil-hidroxitolueno (do inglês, butylated hydroxytoluene); porém, o nome sugerido pela IUPAC é 2,6-di-t-butil-4metilfenol. t-BuOOH-hidroperóxido de t-butilo CICECO-Centro de Investigação em Materiais Cerâmicos e Compósitos m-CPBA-ácido meta-cloroperbenzoico ddupleto ddduplo dupleto DFT-Teoria Funcional da Densidade (do inglês, Density Fuctional Theory) equiv.-equivalente molar ESI-MSionização por "Electrospray" em espectrometria de massa (do inglês, Electrospray Ionization-Mass Spectrometry) ε ε ε ε-coeficiente de absortividade molar (em dm 3 .mol-1 .cm-1) FT-IRespectroscopia de infravermelho com transformadas de Fourier (do inglês, Fourier Transform-InfraRed) GC-FIDcromatrógrafo de gás acoplado a um detector do tipo FID (do inglês, Gas Chromatography Flame Ionization Detector) GC-MS-cromatógrafo de gás acoplado a um detector do tipo MS (do inglês, Gas Chromatography Mass Spectrometer) H 2-1DCP3DMImP-(2,6-diclorofenil),10,15,20-tris(1,3-dimetilimidazolínio-2-il)porfirina
An undergraduate organic chemistry experiment for oil extraction and biodiesel production using a... more An undergraduate organic chemistry experiment for oil extraction and biodiesel production using alternative biomass was developed, whereby oils of avocado, coconut and spent coffee grounds were obtained and submitted to transesterification reaction with CH3OH under NaOH catalysis. Avocado and coffee oils were obtained by typical extraction and coconut oil was obtained through water evaporation of coconut milk in a domestic microwave oven. The commercial oil of licuri (Syagrus coronate), a Brazilian native biomass, was also converted to biodiesel. All four oils and four biodiesels were characterized by 1H-NMR and FTIR, and a comparative study of these spectra reveled that FTIR analyses alone provides enough information to discriminate between oil and biodiesel and confirm transesterification reaction. Besides, the unsaturation degree of all oils was determined by 1H-NMR. A mechanistic proposal concerning the role of NaOH catalysis is presented, excluding the sodium methoxide formation.
Photochemical & Photobiological Sciences, 2004
The photophysics of 3-(benzoxazol-2-yl)-7-(N,N-diethylamino)chromen-2-one was studied in differen... more The photophysics of 3-(benzoxazol-2-yl)-7-(N,N-diethylamino)chromen-2-one was studied in different solvents and in SDS micelles. This compound presents characteristics which include an S(0)---> S(1) ( pi,pi*) transition with a (1)(n,pi*) perturbative component, due to the electronic coupling between the diethylamino group and the coumarin ring, considerable solvatochromism, dual fluorescence and high fluorescence quantum yields in almost all solvents studied. The electronic structure of the S(1) and S(2) excited states permits vibronic coupling between them, making configurational changes of the S(2) excited state possible, leading to the formation of an S(2)(TICT) state. Analysis of the TCSPC data indicates an equilibrium between the S(2)(TICT) and S(1)(LE) states in favour of the former. In protic solvents, the hydrogen bonding between the solvent and the diethylamino moiety results in the formation of an S(2)(HICT) state, making internal conversion an important deactivation process. Quantum mechanical calculations for the isolated molecule show that the diethylamino group in the S(2)(TICT) state is twisted at least 56 degree from the plane of the coumarin ring, with partial electronic decoupling between -NEt(2) and the coumarin ring. This twisting angle must be positively influenced by solute-solvent interactions. [capital Phi](ST) is found to be small, but not negligible. However, Phi (delta) can be considered negligible, an indication that T(1) is a short-lived state. Based on the experimental data and theoretical calculations, the most probable sequence for the first excited states, including the TICT state, is T(1)(n, pi*) < S(2)(TICT) < S(1)(pi,pi*) approximate S(2) (n,pi*).
Journal of Porphyrins and Phthalocyanines, 2009
Cheap and abundant natural products can be transformed into products of higher commercial value. ... more Cheap and abundant natural products can be transformed into products of higher commercial value. One of the approaches for the functionalization of organic compounds is their oxidation in the presence of an oxygen atom donor, under the influence of a suitable catalyst. Metalloporphyrins, with structures based on the well known meso-tetraphenylporphyrin (TPPH2), are amongst the catalysts commonly studied and have demonstrated to be efficient in the oxygenation of organic compounds. These transformations have been studied in the presence of different oxygen atom donors. However, our biomimetic oxidative approach is based on the use of clean and environmentally benign hydrogen peroxide in the presence of metalloporphyrins. This approach will be outlined in this review.
Journal of Photochemistry and Photobiology A: Chemistry, 2008
The solvatochromism and other spectroscopic and photophysical characteristics of four azo dispers... more The solvatochromism and other spectroscopic and photophysical characteristics of four azo disperse dyes, derived from 2-amino-5-nitrothiazole, were evaluated and interpreted with the aid of experimental data and quantum mechanical calculations. For the non-substituted compound two conformers, E and Z, were proposed for the isolated molecules, being the second one considerably less stable. The optimization of these structures in combination with
Química Nova, 2021
OXYGEN IN THE COVID-19 CONTEXT: WHAT WE KNOW ABOUT THE MOLECULE WE BREATHE AND THE CENTRAL ROLE O... more OXYGEN IN THE COVID-19 CONTEXT: WHAT WE KNOW ABOUT THE MOLECULE WE BREATHE AND THE CENTRAL ROLE OF CHEMISTRY. In this work, the role of chemistry in the coronavirus disease 2019 (COVID-19) pandemic is highlighted through the medical oxygen supply crises in Brazil, as an example of oxygen utility in health. Starting from oxygen chemical characterization, the oxygen cycle in nature is discussed to show how oxygen is formed through photosynthesis, followed by the description of the industrial oxygen production from atmospheric air, including physical-chemical aspects. The use of medical oxygen concentrator is presented and how this device works from the chemical point of view. Besides, the noninvasive and painless oximetry is described in terms of how oxygen saturation level in blood is measured using LED - light emitting diode.
RSC Advances
P450-bioinspired Jacobsen/Cell(NEt2) catalysts have been applied in RhB dye oxidation, which is u... more P450-bioinspired Jacobsen/Cell(NEt2) catalysts have been applied in RhB dye oxidation, which is used illegally in food industries of some countries.
Journal of Heterocyclic Chemistry, Mar 1, 2008
Page 1. Mar-Apr 2008 Kinetic Study of meso-Tetraphenylporphyrin Synthesis Under Microwave Irradia... more Page 1. Mar-Apr 2008 Kinetic Study of meso-Tetraphenylporphyrin Synthesis Under Microwave Irradiation 453 Rodrigo De Paula, Maria AF Faustino, Diana CGA Pinto, Maria GPMS Neves, José AS Cavaleiro* University of Aveiro, Department of Chemistry, Campus Santiago. ...
Journal of Molecular Catalysis A: Chemical, 2015
ABSTRACT A new catalytic system based on an immobilized imidazolyl manganese porphyrin for the ox... more ABSTRACT A new catalytic system based on an immobilized imidazolyl manganese porphyrin for the oxidation of olefins is presented. Merrifield resin (MR) and functionalized silica gel (SG) were chosen as supports. The results indicate that the MR system shows high reaction rates, high efficiency with hydrogen peroxide as oxidant and good recyclability up to four times, without a dramatic loss in the catalytic efficiency. The catalytic behavior seems to be strongly influenced by the immobilization reaction conditions. The oxidation reactions performed for cis-cyclooctene, styrene, cyclohexene and geraniol give the corresponding epoxides, with very high selectivity, when the MR system is used. Some considerations concerning the high efficiency of the MR system are put forward.
RSC Advances, 2011
The biomimetic oxidation of lapachol (1) using aqueous hydrogen peroxide as oxidant and chloro[5,... more The biomimetic oxidation of lapachol (1) using aqueous hydrogen peroxide as oxidant and chloro[5,10,15,20-tetrakis(2,6-dichlorophenyl)porphyrinatomanganese(III)] (Mn-Porph) as catalyst is described. A comparison between the obtained results and those described for the oxidation of lapachol using meta-chloroperoxybenzoic acid (m-CPBA) reveals, besides different reaction products, a completely different selectivity. Unlike the m-CPBA approach, where ortho-naphthoquinones are obtained, paranaphthoquinones are highly favoured when using Mn-Porph and H 2 O 2. Moreover, a new lactone is isolated and characterized in the present work.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2013
The steady state and time resolved experiments together with absorption and emission spectroscopi... more The steady state and time resolved experiments together with absorption and emission spectroscopies and quantum chemical calculations have been employed to investigate spectroscopic properties of a xanthone-type compound (ethyl 3,12-dioxopyran[3,2-a]xanthone-2-carboxylate). The spectroscopic data show good agreement with results obtained from quantum chemical calculations. Additionally, this compound shows expressive quantum efficiency for triplet population and a quantum efficiency of singlet oxygen generation very close to unity. Correlations between the nature of singlet and triplet excited states and spectroscopic properties were performed in order to understand the high quantum efficiency of singlet oxygen generation by this compound.
Journal of Photochemistry and Photobiology A: Chemistry, 2004
It was shown that 3-benzoxazol-2-yl-7-(N,N-diethylamino)-chromen-2-one is suitable to perform as ... more It was shown that 3-benzoxazol-2-yl-7-(N,N-diethylamino)-chromen-2-one is suitable to perform as a fluorescent probe, to analyse physical parameters related to organised systems. Micropolarity, microviscosity, critical aggregation and micelle concentration data, in SDS and CTAB micelles, using the proposed compound as fluorescent probe show the compound is allocated, in both micelles, in a strongly polar hydrophilic region (the parameter E T (30) is equal to 61.3 and 61.9 kcal/mol, respectively, in SDS and CTAB micelles, whereas Lippert's f parameter is equal to 0.35). The CMC of SDS in pure water (7.5 × 10 −3 mol/dm 3) agrees with the reported values. For SDS and CTAB micelles in buffered medium (PBS buffer, pH 7.4, NaCl 0.9%, w/w), the estimated critical aggregation concentrations (4.6 × 10 −3 and 9.2 × 10 −4 mol/dm 3 , respectively, for SDS and CTAB) also agree with the results obtained using equivalent conditions.
Journal of Molecular Catalysis A: Chemical, 2011
The oxidation of styrene and derivatives with H 2 O 2 catalyzed by manganese porphyrins in aceton... more The oxidation of styrene and derivatives with H 2 O 2 catalyzed by manganese porphyrins in acetonitrile is described. The effect of the imidazolium substituent on the catalytic efficiency has been also considered. The thermodynamic analysis has indicated that enthalpy rules styrene oxidation when catalysts Mn(Porph)-1 and Mn(Porph)-2 are used whereas the entropy is the driven force for Mn(Porph)-3 and Mn(Porph)-4 catalyzed reactions. Interestingly, an enthalpy-entropy compensation phenomenon is observed when comparing the thermodynamic results obtained for catalysts Mn(Porph)-3 and Mn(Porph)-4. Hammett plots for the studied manganese porphyrins provided small-values, and this is typical for multi-step reactions, indicating that there is no significant charge separation in the transition state. For Mn(Porph)-1 and Mn(Porph)-2 the formation of multiple active species can be put forward whereas for Mn(Porph)-3 and Mn(Porph)-4 a concerted-type mechanism, via metalloxetane intermediate, fits well with the values obtained for those catalysts. The imidazolium-based catalysts have shown to be efficient catalysts in styrene and derivatives oxidation with hydrogen peroxide.
Journal of Mass Spectrometry, 2014
Electrospray ionization mass spectrometry/mass spectrometry in the positive ion mode was used to ... more Electrospray ionization mass spectrometry/mass spectrometry in the positive ion mode was used to investigate the gas-phase chemistry of multicharged ions from solutions of porphyrins with 1,3-dimethylimidazolium-2-yl (DMIM) and 1-methylimidazol-2-yl (MIm) meso-substituents. The studied compounds include two free bases and 12 complexes with transition metals (Cu(II), Zn(II), Mn(III), and Fe(III)). The observed multicharged ions are either preformed or formed during the electrospraying process by reduction or protonation and comprise closed-shell and hypervalent mono-radical and bi-radical ions. The observed extensive and abundant fragmentation of the DMIM and MIm meso-substituents is a characteristic feature of these porphyrins. Fragments with the same mass values can be lost from the meso-substituents either as charged or neutral species and from closed-shell and hypervalent radical ions. Reduction processes are observed for both the free bases and the metallated DMIM porphyrins and occur predominantly by formation of hypervalent radicals that fragment, at low energy collisions, by loss of methyl radicals with formation of the corresponding MIm functionalities. These findings confirm that, when using electrospray ionization, reduction is an important characteristic of cationic meso-substituted tetrapyrrolic macrocycles, always occurring when delocalization of the formed hypervalent radicals is possible. For the Fe(III) and Mn(III) complexes, reduction of the metal centers is also observed as the predominant fragmentation of the corresponding reduced ions through losses of charged fragments testifies. The fragmentation of the closed-shell ions formed by protonation of the MIm porphyrins mirrors the fragmentation of the closed-shell ions of their DMIM counterparts.
Journal of Heterocyclic Chemistry, 2008
Page 1. Mar-Apr 2008 Kinetic Study of meso-Tetraphenylporphyrin Synthesis Under Microwave Irradia... more Page 1. Mar-Apr 2008 Kinetic Study of meso-Tetraphenylporphyrin Synthesis Under Microwave Irradiation 453 Rodrigo De Paula, Maria AF Faustino, Diana CGA Pinto, Maria GPMS Neves, José AS Cavaleiro* University of Aveiro, Department of Chemistry, Campus Santiago. ...