Maurício Cruz - Academia.edu (original) (raw)

Papers by Maurício Cruz

Research paper thumbnail of Interaction of polyelectrolyte complex between sodium alginate and chitosan dimers with a single glyphosate molecule: A DFT and NBO study

Carbohydrate polymers, Jan 15, 2018

The formation of a polyelectrolyte complex through dimers of alginate and chitosan in the presenc... more The formation of a polyelectrolyte complex through dimers of alginate and chitosan in the presence of sodium cations (SA/CS), and its interaction with the glyphosate herbicide, has been investigated at the DFT level (B3LYP/6‒311+G(d,p)). The lowest energy structure for SA/CS presents one Na cation coordinated to both dimers and formation of two H-bonds involving COO- and NH. The coordination energy of Na contributes with about 40% of the total complex stabilization energy. LMOEDA method indicates important contribution of covalent nature to stabilization of SA/CS. This result is corroborated by NBO analysis which shows high contribution of lp(O)→σ(NH) overlapping, with average energy of 30 kcal mol for the formed H-bonds. Two water molecules neighboring the complex increases its stability and promotes an octahedral coordination arrangement around Na. The glyphosate interacts with SA/CS coordinating to Na and bonding to the chitosan dimer by H-bond, in agreement to performed fluoresc...

Research paper thumbnail of DFT Study of Ethanol Dehydration Catalysed by Hematite

RSC Adv., 2016

Ethanol dehydration process: energy barrier and rate constant, k(T), at room temperature. Gas pha... more Ethanol dehydration process: energy barrier and rate constant, k(T), at room temperature. Gas phase and hematite model catalytic (FenO3/2n) results.

Research paper thumbnail of Experimental and theoretical studies on the complexes between Cisplatin and Guanidinoacetic Acid

Polyhedron, 2015

Abstract Cisplatin, cis -dichlorodiammineplatinum(II) is one the most employed antineoplasic drug... more Abstract Cisplatin, cis -dichlorodiammineplatinum(II) is one the most employed antineoplasic drugs, exhibiting activity for different types of tumors. Cisplatin resistance can be related to its reduced uptake or retention, causing the decrease of the platinum–DNA adduct. This is attributed to cisplatin binding to other cellular components, causing its deactivation or damage to its normal biochemical pathway. Several studies with a focus on elucidating cisplatin binding to compounds present in cells have been conducted. In the present study, the interaction of cisplatin with one potential O and N-donor ligand, guanidinoacetic acid, was investigated, an amino acid found at high concentrations in the kidney and liver, organs where the drug accumulates. In vitro GAA and cisplatin interaction was studied in aqueous medium at the same ionic strength (0.1 mol L −1 KCl) and temperature (36.5 °C) as fluids of the body. Potentiometric and NMR ( 1 H and 195 Pt) analyses have been done, with the determination of stability constants and theoretical calculations for the principal structures involved. Results showed that GAA may be one of the potential biomolecules of cisplatin since, under the conditions of temperature and ionic strength of the body at around pH 7, part of cisplatin interacted with GAA to form [Pt(NH 3 ) 2 (HGAA) 2 ] 2+ . Optimization of this species, [Pt(NH 3 ) 2 (HGAA) 2 ] 2+ was carried out using the gaussian 03 package with the B3LYP function in combination with LANL2DZ (6–311G(d,p)), yielding a planar sphere coordination around Pt(II) and also O–H intramolecular interactions in the complex. The results on speciation for cisplatin/GAA systems could be of great interest since GAA may be one of the potential binding species of cisplatin, especially in the study of 5:1 cisplatin/GAA ratio (found in rats, for example).

Research paper thumbnail of Density Functional Theory Study of Benzene Adsorption on Small Pd and Pt Clusters

Journal of Physical Chemistry C, 2007

ABSTRACT Restricted and unrestricted B3LYP/LANL2DZ and B3LYP/6-31G(d) calculations are employed t... more ABSTRACT Restricted and unrestricted B3LYP/LANL2DZ and B3LYP/6-31G(d) calculations are employed to study the adsorption of benzene on small Pd7, Pd(7+3), Pt7, and Pt(7+3) clusters. Restricted calculations give the bridge-30 adsorption site as the most stable for adsorption of benzene on Pd7 cluster, while on Pd(7+3) benzene is strongly tilted, leading to an adsorption mode where two benzene π-bonds more strongly interact with the metal cluster. Unrestricted calculations (triplet spin state) strongly favor the tilted conformations so that on both Pd7 and on Pd(7+3) the tilted di-π-hcp adsorption mode is the most stable. On the Pt7 and Pt(7+3) clusters even the restricted calculations lead to the tilted di-π adsorption mode as the most stable, a result that is reinforced by the unrestricted formalism, which also favors the tilted adsorption mode. The differences between the restricted and the unrestricted calculations are much larger for platinum than for palladium, which is related to the fact that atomic palladium has closed shell electronic configuration while atomic platinum has open shell electronic configuration. The adsorption process is dominated by electron donation from the highest occupied molecular orbital of benzene to the lowest unoccupied molecular orbital of the metal clusters.

Research paper thumbnail of Density functional theory study of benzene adsorption on small Pd and Pt clusters

ABSTRACT Restricted and unrestricted B3LYP/LANL2DZ and B3LYP/6-31G(d) calculations are employed t... more ABSTRACT Restricted and unrestricted B3LYP/LANL2DZ and B3LYP/6-31G(d) calculations are employed to study the adsorption of benzene on small Pd7, Pd(7+3), Pt7, and Pt(7+3) clusters. Restricted calculations give the bridge-30 adsorption site as the most stable for adsorption of benzene on Pd7 cluster, while on Pd(7+3) benzene is strongly tilted, leading to an adsorption mode where two benzene π-bonds more strongly interact with the metal cluster. Unrestricted calculations (triplet spin state) strongly favor the tilted conformations so that on both Pd7 and on Pd(7+3) the tilted di-π-hcp adsorption mode is the most stable. On the Pt7 and Pt(7+3) clusters even the restricted calculations lead to the tilted di-π adsorption mode as the most stable, a result that is reinforced by the unrestricted formalism, which also favors the tilted adsorption mode. The differences between the restricted and the unrestricted calculations are much larger for platinum than for palladium, which is related to the fact that atomic palladium has closed shell electronic configuration while atomic platinum has open shell electronic configuration. The adsorption process is dominated by electron donation from the highest occupied molecular orbital of benzene to the lowest unoccupied molecular orbital of the metal clusters.

Research paper thumbnail of The Effect of Gamma-Al 2 O 3 Support on the NO Adsorption on Pd 4 Cluster

Journal of the Brazilian Chemical Society, 2016

The effect of γ-Al 2 O 3 support on the NO adsorption on Pd 4 clusters was investigated by means ... more The effect of γ-Al 2 O 3 support on the NO adsorption on Pd 4 clusters was investigated by means of density functional theory (DFT) calculations. Pd 4 adsorbed on γ-Al 2 O 3 (represented by a Al 14 O 24 H 6 cluster) changes its preferential geometry from tetrahedral to a distorted planar structure. The alumina support promotes a higher dispersion in the palladium catalyst and reduces the NO adsorption energy to-25.6 kcal mol-1 (computed at B3LYP/LANL2DZ/6-311+G(d)), in close agreement with the experimental value of-27.2 kcal mol-1. On the bare planar Pd 4 cluster the NO molecule adsorbs in a bridge arrangement, with adsorption energy of-41.2 kcal mol-1. Adsorption on the tetrahedral Pd 4 cluster occur preferentially in an atop mode, with adsorption energy of-30.6 kcal mol-1. Charge density analysis show that the electron flux between the NO molecule and Pd 4 depends on the adsorption form, with back-donation being stronger in the bridge adsorption mode.

Research paper thumbnail of Interaction of polyelectrolyte complex between sodium alginate and chitosan dimers with a single glyphosate molecule: A DFT and NBO study

Carbohydrate polymers, Jan 15, 2018

The formation of a polyelectrolyte complex through dimers of alginate and chitosan in the presenc... more The formation of a polyelectrolyte complex through dimers of alginate and chitosan in the presence of sodium cations (SA/CS), and its interaction with the glyphosate herbicide, has been investigated at the DFT level (B3LYP/6‒311+G(d,p)). The lowest energy structure for SA/CS presents one Na cation coordinated to both dimers and formation of two H-bonds involving COO- and NH. The coordination energy of Na contributes with about 40% of the total complex stabilization energy. LMOEDA method indicates important contribution of covalent nature to stabilization of SA/CS. This result is corroborated by NBO analysis which shows high contribution of lp(O)→σ(NH) overlapping, with average energy of 30 kcal mol for the formed H-bonds. Two water molecules neighboring the complex increases its stability and promotes an octahedral coordination arrangement around Na. The glyphosate interacts with SA/CS coordinating to Na and bonding to the chitosan dimer by H-bond, in agreement to performed fluoresc...

Research paper thumbnail of DFT Study of Ethanol Dehydration Catalysed by Hematite

RSC Adv., 2016

Ethanol dehydration process: energy barrier and rate constant, k(T), at room temperature. Gas pha... more Ethanol dehydration process: energy barrier and rate constant, k(T), at room temperature. Gas phase and hematite model catalytic (FenO3/2n) results.

Research paper thumbnail of Experimental and theoretical studies on the complexes between Cisplatin and Guanidinoacetic Acid

Polyhedron, 2015

Abstract Cisplatin, cis -dichlorodiammineplatinum(II) is one the most employed antineoplasic drug... more Abstract Cisplatin, cis -dichlorodiammineplatinum(II) is one the most employed antineoplasic drugs, exhibiting activity for different types of tumors. Cisplatin resistance can be related to its reduced uptake or retention, causing the decrease of the platinum–DNA adduct. This is attributed to cisplatin binding to other cellular components, causing its deactivation or damage to its normal biochemical pathway. Several studies with a focus on elucidating cisplatin binding to compounds present in cells have been conducted. In the present study, the interaction of cisplatin with one potential O and N-donor ligand, guanidinoacetic acid, was investigated, an amino acid found at high concentrations in the kidney and liver, organs where the drug accumulates. In vitro GAA and cisplatin interaction was studied in aqueous medium at the same ionic strength (0.1 mol L −1 KCl) and temperature (36.5 °C) as fluids of the body. Potentiometric and NMR ( 1 H and 195 Pt) analyses have been done, with the determination of stability constants and theoretical calculations for the principal structures involved. Results showed that GAA may be one of the potential biomolecules of cisplatin since, under the conditions of temperature and ionic strength of the body at around pH 7, part of cisplatin interacted with GAA to form [Pt(NH 3 ) 2 (HGAA) 2 ] 2+ . Optimization of this species, [Pt(NH 3 ) 2 (HGAA) 2 ] 2+ was carried out using the gaussian 03 package with the B3LYP function in combination with LANL2DZ (6–311G(d,p)), yielding a planar sphere coordination around Pt(II) and also O–H intramolecular interactions in the complex. The results on speciation for cisplatin/GAA systems could be of great interest since GAA may be one of the potential binding species of cisplatin, especially in the study of 5:1 cisplatin/GAA ratio (found in rats, for example).

Research paper thumbnail of Density Functional Theory Study of Benzene Adsorption on Small Pd and Pt Clusters

Journal of Physical Chemistry C, 2007

ABSTRACT Restricted and unrestricted B3LYP/LANL2DZ and B3LYP/6-31G(d) calculations are employed t... more ABSTRACT Restricted and unrestricted B3LYP/LANL2DZ and B3LYP/6-31G(d) calculations are employed to study the adsorption of benzene on small Pd7, Pd(7+3), Pt7, and Pt(7+3) clusters. Restricted calculations give the bridge-30 adsorption site as the most stable for adsorption of benzene on Pd7 cluster, while on Pd(7+3) benzene is strongly tilted, leading to an adsorption mode where two benzene π-bonds more strongly interact with the metal cluster. Unrestricted calculations (triplet spin state) strongly favor the tilted conformations so that on both Pd7 and on Pd(7+3) the tilted di-π-hcp adsorption mode is the most stable. On the Pt7 and Pt(7+3) clusters even the restricted calculations lead to the tilted di-π adsorption mode as the most stable, a result that is reinforced by the unrestricted formalism, which also favors the tilted adsorption mode. The differences between the restricted and the unrestricted calculations are much larger for platinum than for palladium, which is related to the fact that atomic palladium has closed shell electronic configuration while atomic platinum has open shell electronic configuration. The adsorption process is dominated by electron donation from the highest occupied molecular orbital of benzene to the lowest unoccupied molecular orbital of the metal clusters.

Research paper thumbnail of Density functional theory study of benzene adsorption on small Pd and Pt clusters

ABSTRACT Restricted and unrestricted B3LYP/LANL2DZ and B3LYP/6-31G(d) calculations are employed t... more ABSTRACT Restricted and unrestricted B3LYP/LANL2DZ and B3LYP/6-31G(d) calculations are employed to study the adsorption of benzene on small Pd7, Pd(7+3), Pt7, and Pt(7+3) clusters. Restricted calculations give the bridge-30 adsorption site as the most stable for adsorption of benzene on Pd7 cluster, while on Pd(7+3) benzene is strongly tilted, leading to an adsorption mode where two benzene π-bonds more strongly interact with the metal cluster. Unrestricted calculations (triplet spin state) strongly favor the tilted conformations so that on both Pd7 and on Pd(7+3) the tilted di-π-hcp adsorption mode is the most stable. On the Pt7 and Pt(7+3) clusters even the restricted calculations lead to the tilted di-π adsorption mode as the most stable, a result that is reinforced by the unrestricted formalism, which also favors the tilted adsorption mode. The differences between the restricted and the unrestricted calculations are much larger for platinum than for palladium, which is related to the fact that atomic palladium has closed shell electronic configuration while atomic platinum has open shell electronic configuration. The adsorption process is dominated by electron donation from the highest occupied molecular orbital of benzene to the lowest unoccupied molecular orbital of the metal clusters.

Research paper thumbnail of The Effect of Gamma-Al 2 O 3 Support on the NO Adsorption on Pd 4 Cluster

Journal of the Brazilian Chemical Society, 2016

The effect of γ-Al 2 O 3 support on the NO adsorption on Pd 4 clusters was investigated by means ... more The effect of γ-Al 2 O 3 support on the NO adsorption on Pd 4 clusters was investigated by means of density functional theory (DFT) calculations. Pd 4 adsorbed on γ-Al 2 O 3 (represented by a Al 14 O 24 H 6 cluster) changes its preferential geometry from tetrahedral to a distorted planar structure. The alumina support promotes a higher dispersion in the palladium catalyst and reduces the NO adsorption energy to-25.6 kcal mol-1 (computed at B3LYP/LANL2DZ/6-311+G(d)), in close agreement with the experimental value of-27.2 kcal mol-1. On the bare planar Pd 4 cluster the NO molecule adsorbs in a bridge arrangement, with adsorption energy of-41.2 kcal mol-1. Adsorption on the tetrahedral Pd 4 cluster occur preferentially in an atop mode, with adsorption energy of-30.6 kcal mol-1. Charge density analysis show that the electron flux between the NO molecule and Pd 4 depends on the adsorption form, with back-donation being stronger in the bridge adsorption mode.