RESUMO
Quaternary or spirocyclic 3-substituted-3-hydroxy-2-oxindole is considered a privileged scaffold. In other words, it is a molecular core present on several compounds with a wide spectrum of biological activities. Among its precursors, activated ketones (isatin nucleus) can be used as interesting starting points to Morita-Baylis-Hillman adducts derivatives, a class of compounds with good cytotoxic potential. In this paper, we present the synthesis, anti-proliferative activity against lung cancer cell line and a theoretical conformational study of 21 of Morita-Baylis-Hillman adducts from isatin derivatives, by DFT quantum chemical calculations, followed by a SAR and QSAR analysis. Besides, an efficient synthetic protocol and good biological activity profile were highlighted interesting observations about 1H NMR experimental spectra, molecular modeling results and crystallographic data available.
Assuntos
Antineoplásicos/química , Antineoplásicos/farmacologia , Técnicas de Química Sintética , Isatina/química , Isatina/farmacologia , Modelos Teóricos , Espectroscopia de Prótons por Ressonância Magnética , Antineoplásicos/síntese química , Linhagem Celular Tumoral , Relação Dose-Resposta a Droga , Humanos , Concentração Inibidora 50 , Isatina/análogos & derivados , Isatina/síntese química , Modelos Moleculares , Estrutura Molecular , Relação Quantitativa Estrutura-AtividadeRESUMO
Solid dispersions have been used as a strategy to improve the solubility, dissolution rate, and bioavailability of poor water-soluble drugs. The increase of the dissolution rate presented by (5Z)-3-(4-chloro-benzyl)-5-(4-nitro-benzylidene)-imidazolidine-2,4-dione (LPSF/FZ4) from the solid dispersions is related to the existence of intermolecular interactions of hydrogen bond type (>N-H···O<) between the amide group (>N-H) of the LPSF/FZ4 and the ether group (-O-) of the polyethyleneglycol polymer, or the carbonyl (C=O) of the polyvinylpyrrolidone polymer (PVP). The intensity of these interactions is directly reflected in the morphology acquired by LPSF/FZ4 in these systems, where a new solid phase, in the form of amorphous aggregates of irregular size, was identified through scanning electron microscopy and confirmed in the characterizations achieved using X-ray diffraction and thermal analysis of DSC. The solid dispersions with the polymer PVP, in higher concentrations, were revealed to be the best option to be used in the formulations of LPSF/FZ4 in both theoretical and experimental studies.
Assuntos
Sistemas de Liberação de Medicamentos , Hidantoínas/química , Esquistossomicidas/química , Formas de Dosagem , Portadores de Fármacos , Composição de Medicamentos , Hidantoínas/farmacologia , Modelos Moleculares , Polietilenoglicóis/química , Polímeros/química , Povidona/química , Esquistossomicidas/farmacologia , SolubilidadeRESUMO
The N-alkylated derivatives from nitrofurazone were synthesised and evaluated in vitro for their efficacy as antimicrobial agents against representative strains, including methicillin-resistant Staphylococcus aureus (MRSA). The derivative 2a demonstrated greater activity than the prototype and was comparable to currently used antimicrobial drugs.
Assuntos
Antibacterianos , Antifúngicos , Desenho de Fármacos , Nitrofurazona , Antibacterianos/síntese química , Antibacterianos/química , Antibacterianos/farmacologia , Antifúngicos/síntese química , Antifúngicos/química , Antifúngicos/farmacologia , Testes de Sensibilidade Microbiana , Estrutura Molecular , Nitrofurazona/síntese química , Nitrofurazona/química , Nitrofurazona/farmacologia , Relação Estrutura-AtividadeRESUMO
A theoretical study of hydrogen bond strength and bond properties in the C2H2â¯(HF)-T, C2H2â¯2(HF)-T, C2H2â¯2(HF), C2H2â¯3(HF) and C2H2â¯4(HF) complexes was carried out at the B3LYP/6-311++G(d,p) theory level. In these systems, a strength competition between the πâ¯H and Câ¯H interactions was examined. Specifically the Fâ¯H hydrogen bond, its properties were studied through a comparison between the hydrogen fluoride and the higher-order complexes (trimer, tetramer and pentamer). Regarding the electronic properties, the hydrogen bond strength could not be determined by the supermolecule approach. Thus, the hydrogen bond energies were computed via NBO calculations. Additionally to NBO, the ChelpG charge calculations were used to interpret the intermolecular charge transfer. The QTAIM integrations were useful to predict the covalent character of the πâ¯H, Câ¯H and Fâ¯H hydrogen bonds. Moreover, values of hybrid orbitals (s and p) and atomic radii were also determined in order to justify the red shifts in the stretch frequencies of the HF bonds.
RESUMO
This theoretical work exhibits a new systematic study of structural parameters, electronic properties, infrared vibration modes, and molecular topography of hydrogen complexes, namely linear-type HCNâ¯HX and T-type C2H2â¯HX (X = F, Cl, CN, and CCH). Ideally, the knowledge of the ternary systems of C2H2â¯HCNâ¯HF and HCNâ¯HCNâ¯HF whose subparts integrate the linear and T-shaped complexes were used to give support in this current research. By means of computational calculations carried out in both levels B3LYP and MP2, the variations of the HX bond lengths are clearly overestimated in the HCNâ¯HX linear complexes. In agreement with the analyses of the electrostatic potentials, the higher intermolecular energies of these complexes agree with the larger red-shifts in the stretch frequencies in HX. Also, the QTAIM descriptors and NBO calculations were used to inspect the interaction strength as well as to confirm the π cloud as a proton accepting center. By taking into account the absorption intensity ratio as a standard parameter to predict the interaction strength and intermolecular characterization, the formalism of the charge-charge flux-overlap modified (CCFO) was applied.
RESUMO
Through the B3LYP/6-311++G(d,p) calculations, theoretical studies of structural parameters, electronic properties, infrared vibration modes, and charge density topologies on the C2H4OâââHX and C2H5NâââHX (X = F or O-F) heterocylic hydrogen complexes are presented. The H-bond distances and high energies point out strong contacts and stable interactions in these complexes, and the relationships between the frequency shifts on the H-F and H-O bonds as well as O-F σ-holes with the interaction strength are the benchmarks of this current work. The computations of charge transfer amounts in light of the ChelpG and NBO approaches revealed a separation of charge density on the O-F σ-holes, whose statement is reinforced by the QTAIM descriptors. Despite that OâââH and NâââH H-bonds have been characterized as closed-shell interactions, qualitatively the appearance of a partial covalent profile also was unveiled by the QTAIM protocol.
RESUMO
The dihydrogen bond complexes (H3SiHâââHOX) and halogen bond complexes (H3SiHâââXOH) formed between SiH4 and hypohalous acids HOX (X = F, Cl, and Br) have been studied at the MP2/6-311++G(2d,2p) computational level. The analyses of structure and infrared vibration frequencies have revealed tendencies in the red shifts and blue shifts of the stretch frequencies of the Si-H, H-O, and O-X bonds. Besides the computation of the interaction energies, punctual atomic charges and charge transference amounts were determined at light of the Natural Bond Orbital (NBO) approach, by which the quantifications of the s- and p-characters of hydrogen, oxygen, and silicon also were useful to unveil the frequency shifts aforementioned. With the purpose to elucidate the donor/acceptor interface along the charge transfer mechanism between the dihydrogen bonds and halogen bonds, the application of the hierarchical cluster analysis (HCA) and principal component analysis (PCA) chemometric techniques were useful in this regard. Moreover, the interaction strengths of the H3SiHâââHOX and H3SiHâââXOH complexes was computed through a model that embodies the frequency shifts and topological parameters derived from quantum theory of atoms in molecules (QTAIM).
RESUMO
In this theoretical work, the tetrahydroborate ion (BH4(-)) was used as proton acceptor in the formation of the YCC-Hâ¯BH4(-) complexes (Y=H, CH3, CCl3 and CF3). Using B3LYP/6-311++G(d,p) level of theory, the results of structure corroborate with the analyses of infrared spectra showing that the changes in the bond lengths are in good agreement with the frequency shifts of the HCC-H, H3CCC-H, Cl3CCC-H and F3CCC-H proton donors. Based on the calculations carried out by the Quantum Theory of Atoms in Molecules (QTAIM), the reductions of electronic density corroborate with the red shifts in the frequencies of the C-H bonds. In addition to that, the C-H bonds are polarized because the contributions of s orbital diminish whereas of p increase. In line with this, the variations on the atomic radii computed via QTAIM calculations show that carbon outweigh hydrogen as follows (ΔrC>ΔrH). This scenario is indirectly supported by the Bent's rule of the chemical bonding. Although the interaction energies (corrected with BSSE and ZPE) vary between -19 and -67 kJ mol(-1), these complexes interact without covalent character.
Assuntos
Boro/química , Elétrons , Modelos Moleculares , Conformação Molecular , Teoria Quântica , Espectrofotometria Infravermelho , Termodinâmica , VibraçãoRESUMO
In this work, the existence of multiple interactions in heterocyclic complexes of C2H4Oâ¯nHCCl3 and C2H4Sâ¯nHCCl3 with n=2 and 3 was unveiled at the B3LYP/6-311++G(d,p) level of theory. The forward analyses of the vibrational spectra revealed the appearing of red-shifts in the H-C bond. In agreement with this and through the optimized geometries of these systems, an increase in the H-C bond length was also observed. Besides Oâ¯H and Sâ¯H, other hydrogen bonds formed between chlorineâ¯hydrogen and mainly the halogen interactions formed by chlorineâ¯chlorine were identified. Thereby, the vibration spectra of the heterocyclic complexes were reanalyzed with the purpose to locate new red-shifts, although only those characterized in H-C have been detected up to then. In addition to the correlation between the frequencies shifted to downward values followed by increases in the bond lengths, the interpretation of the red-shifts was conducted by means of the Bent rule of the hybridization theory. The interaction strength was examined in several viewpoints, and one of them was the relationship between the H-bond energies and the intermolecular electronic density computed by means of the Quantum Theory of Atoms in Molecules (QTAIM). Moreover, the prediction of the interaction strength was also made through the combination between vibration modes (red-shifts) and variation of topological parameters, such as the electronic density and Laplacian of the proton donor bond (C-H).
Assuntos
Halogênios/química , Compostos Heterocíclicos/química , Elétrons , Ligação de Hidrogênio , Modelos Moleculares , Conformação Molecular , Espectrofotometria InfravermelhoRESUMO
The interactions of arachno-B(5)H(11) with N(2) and O(2) were theoretically studied. In the B(5)H(11)···N(2) and B(5)H(11)···O(2) complexes, the terminal hydrogens of B(5)H(11) work as electron donors whereas the bridge ones as electron acceptors. The optimized structures and the corresponding harmonic vibration spectra were investigated through the MP2/aug-cc-pVDZ level of theory. In order to characterize the hydrogen bonds, the topological calculations inherent to the QTAIM protocol and MEP analysis were carried out. The NBO analyses were useful in the interpretation of the red-shifts and blue-shifts on the stretch frequencies of the proton donors, of course in agreement with the Bent rule for the chemical bonding as well as by the conceptions of hyperconjugation or hybridization.
RESUMO
In this theoretical work, a new idea about cooperativity in intermolecular clusters of CnHmâââHCNâââHW stabilized by hydrogen bonds composed by lone-electron pairs (nitrogen) and π clouds (C = C and C ≡ C) as proton acceptors is developed. The structural study and vibrational analysis have pointed out deformations in the intermolecular clusters caused by the HW terminal proton-donor, in which if W = fluorine the largest perturbation occurs. On the contrary, the HCN molecule is considered an intermolecular mediator because its structure is practically unaltered upon the formation of the trimolecular complexes. In order to understand the real contribution of the proton-donor either mediator (HCN) or terminal (HW with W = CN or F), a chemometric analysis was performed uniquely to discover which interaction plays a key role in the collapse of the cooperative effect. The formation of strongest interactions leads to more drastic variations in the energy distribution. In this way, the application of the quantum theory of atoms in molecules (QTAIM) has been extremely important because the hydrogen bond strengths followed by indiciums of covalence were predicted, and therefore the cooperative effect could be understood at last.
RESUMO
B3LYP calculations, ChelpG atomic charges, and quantum theory of atoms in molecules (QTAIM) integrations were used to investigate the binary (1:1) and ternary (1:2) hydrogen-bonded complexes formed by aziridine (1) and ammonia (2). In a series of analysis, geometry data, electronic parameters, vibrational oscillators, and topological descriptors were used to evaluate hydrogen bond strength, and additionally to determine the more prominent molecular deformations upon the formation of C(2)H(5)N···NH(3) (1:1) and C(2)H(5)N···2NH(3) (1:2) systems. Taking a spectroscopic viewpoint, results obtained from analysis of the harmonic infrared spectrum were examined. From these, new vibrational modes and red- and blue-shifts related to the stretch frequencies of either donors or acceptors of protons were identified. Furthermore, the molecular topology of the electronic density modeled in accord with QTAIM was absolutely critical in defining bond critical points (BCP) and ring critical points (RCP) on the heterocyclic structures. Taking all the results together allowed us to identify and characterize all the N···H hydrogen bonds, as well as the strain ring of the aziridine and its stability.
Assuntos
Amônia/química , Aziridinas/química , Simulação por Computador , Modelos Moleculares , Ligação de Hidrogênio , Modelos Químicos , Conformação Molecular , Teoria Quântica , Espectrofotometria Infravermelho , TermodinâmicaRESUMO
A theoretical study of structural, electronic, topological and vibrational parameters of the ternary hydrogen-bonded complexes C(2)H(4)O···2HF, C(2)H(5)N···2HF and C(2)H(4)S···2HF is presented here. Different from binary systems with a single proton donor, the tricomplexes have the property of forming multiple hydrogen bonds, which are analyzed from a structural and vibrational point of view, but verified only by means of the quantum theory of atoms in molecules (QTAIM). As traditionally done in the hydrogen bond theory, the charge transfer between proton donors and acceptors was computed using the CHELPG calculations, which also revealed agreement with dipole moment variation and a cooperative effect on the tricomplexes. Furthermore, redshift events on proton donor bonds were satisfactorily identified, although, in this case, an absence of experimental data led to the use of a theoretical argument to interpret these spectroscopic shifts. It was therefore the use of the QTAIM parameters that enabled all intermolecular vibrational modes to be validated. The most stable tricomplex in terms of energy was identified via the strength of the hydrogen bonds, which were modeled as directional and bifurcated.
Assuntos
Compostos Heterocíclicos/química , Modelos Moleculares , Teoria Quântica , Configuração de Carboidratos , Ligação de Hidrogênio , Reprodutibilidade dos TestesRESUMO
The present study investigates the release mechanism of benznidazole (BNZ) in solid dispersions with polyethylene glycol 6000 (PEG 6000) and polyvinylpirrolydone K-30 (PVP K-30), with a view to observing the increase in solubility of BNZ in water in the presence of these two hydrophilic polymers. The interaction of BNZ with the polymers was evaluated using scanning electron microscopy, Fourier-transformation infrared spectroscopy, differential scanning calorimetry, X-ray diffraction, and in vitro dissolution tests, and a theoretical study of molecular modeling was also carried out. The drug-polymer interaction was studied trough molecular modeling, using density functional theory with the B3LYP exchange correlation function. The corrected interaction energies were calculated to be -20.9 kJ/mol with PVP and -6.6 kJ/mol with PEG. The experimental and theoretical results indicate that a powerful interaction occurred between BNZ and the polymers, which was especially strong in the case of PVP, and that this interaction contributed to improvement of BNZ solubility.
Assuntos
Portadores de Fármacos/química , Composição de Medicamentos/métodos , Nitroimidazóis/administração & dosagem , Polietilenoglicóis/química , Povidona/química , Tripanossomicidas/administração & dosagem , Varredura Diferencial de Calorimetria , Estabilidade de Medicamentos , Interações Hidrofóbicas e Hidrofílicas , Microscopia Eletrônica de Varredura , Modelos Moleculares , Estrutura Molecular , Nitroimidazóis/química , Solubilidade , Espectroscopia de Infravermelho com Transformada de Fourier , Propriedades de Superfície , Tripanossomicidas/química , Difração de Raios XRESUMO
A theoretical study is presented with the aim to investigate the molecular properties of intermolecular complexes formed by the monomeric units of polyvinylpyrrolidone (PVP) or polyethyleneglycol (PEG) polymers and a set of four imidazolidine (hydantoine) derivatives. The substitution of the carbonyl groups for thiocarbonyl in the hydantoin scaffold was taken into account when analyzing the effect of the hydrogen bonds on imidazolidine derivatives. B3LYP/6-31G(d,p) calculations and topological integrations derived from the quantum theory of atoms in molecules (QTAIM) were applied with the purpose of examining the N-H···O hydrogen bond strengths formed between the amide group of the hydantoine ring and the oxygen atoms of PVP and PEG polymers. The effects caused by the N-H···O interaction fit the typical evidence for hydrogen bonds, which includes a variation in the stretch frequencies of the N-H bonds. These frequencies were identified as being vibrational red-shifts because their values decreased. Although the values of such calculated interaction energies are between 12 and 33 kJ mol(-1), secondary intermolecular interactions were also identified. One of these secondary interactions is formed through the interaction of the benzyl hydrogen atoms with the oxygen atoms of the PVP and PEG structures. As such, we have analyzed the stretch frequencies on the C-H bonds of the benzyl groups, and blue-shifts were identified on these bonds. In this sense, the intermolecular systems formed by hydantoine derivatives and PVP/PEG monomers were characterized as a mix of red-shifting and blue-shifting hydrogen-bonded complexes.
Assuntos
Imidazolidinas/química , Polímeros/química , Teoria Quântica , Ligação de Hidrogênio , Modelos Moleculares , Modelos Teóricos , Polietilenoglicóis/química , Povidona/química , TermodinâmicaRESUMO
This theoretical study presents a comparative analysis of the molecular properties of heterocyclic (C2H4O...HF and C2H5...HF) and homocyclic (C3H6...HF) hydrogen-bonded complexes. Initially, the equilibrium geometries of these complexes were analyzed in detail at the B3LYP/6-311++G(d,p) level of theory. Subsequently, the interaction energies and polarizabilities were also evaluated, as well as the infrared stretch frequencies and absorption intensities. In addition, by combining intermolecular criteria and charge density concepts, calculations of Bader's theory of atoms in molecules were used to determine the maxima and minima for electron density in order to measure the strength of the n...H and ppi...H hydrogen bonds. Finally, the possibility of an F...H(alpha) secondary interaction between the fluoride (F) of hydrogen fluoride and the axial hydrogen atoms (H(alpha)) of the C2H4O and C2H5N heterocyclic rings was explored.
Assuntos
Aziridinas/química , Ciclopropanos/química , Óxido de Etileno/química , Ácido Fluorídrico/química , Modelos Químicos , Modelos Moleculares , Ligação de Hidrogênio , Computação MatemáticaRESUMO
We presents a chemometrical study of the intermolecular properties of the C(2)H(4)O...HX and C(2)H(5)N... HX hydrogen-bonded complexes with X = F, CN, NC, and CCH. Through the MP2 perturbation theory and B3LYP hybrid functional, as well as modifications on 6-31ijGk basis sets with i = triple-zeta, j = diffuse and k = polarization functions, systematic tendencies in the R((n...HX)) hydrogen bond distances and upsilon((n...HX)) stretch frequencies were determined by the hierarchical cluster analysis, two level factorial designs and principal component analysis. Based on well-fitted math models, not only because polarization functions provide a great variance on statistical analysis, but this basis set reproduces more efficiently the available experimental results. Moreover, independent of whether the quality on basis set is increased, the effects yielded by both DFT and MP2 were not considered important in the statistical analysis.
Assuntos
Acetona/química , Acetonitrilas/química , Modelos Químicos , Ligação de HidrogênioRESUMO
The geometries of three isomers of the C2H4O...2HF tri-molecular heterocyclic hydrogen-bonded complex were examined through B3LYP/aug-cc-pVDZ calculations. Analysis of structural parameters, determination of CHELPG (charge electrostatic potential grid) intermolecular charge transfer, interpretation of infrared stretching modes, and Bader's atoms in molecules (AIM) theory calculations was carried out in order to characterize the hydrogen bonds in each isomer of the C2H4O...2HF complex. The most stable structure was determined through the identification of hydrogen bonds between C2H4O and HF, (O...H), as well as in the hydrofluoric acid dimer, (HF(D-R)...HF(D)). However, the existence of a tertiary interaction (F(lambda)...H(alpha)) between the fluoride of the second hydrofluoric acid and the axial hydrogen atoms of C2H4O was decisive in the identification of the preferred configuration of the C2H4O...2HF system.