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1.
Phys Chem Chem Phys ; 23(8): 4784-4795, 2021 Mar 04.
Artigo em Inglês | MEDLINE | ID: mdl-33599640

RESUMO

The structural stability, charge transfer effects and strength of the spin-orbit couplings in different Ni(ii)-ligand complexes have been studied at the DFT (B3LYP and CAM-B3LYP) and coupled cluster (DLPNO-CCSD(T)) levels of theory. Accordingly, two different, porphyrin- and diketo-pyrphyrin-based four-coordination macrocycles as planar ligands as well as pyridine (or pyrrole) and mesylate anion molecular groups as vertical ligands were considered in order to build metal-organic complexes with octahedral coordination configurations. For each molecular system, the identification of equilibrium geometries and the intersystem crossing (the minimum energy crossing) points between the potential energy surfaces of the singlet and triplet spin states is followed by computing the spin-orbit couplings between the two spin states. Structures, based on the diketo-pyrphyrin macrocycle as the planar ligand, show stronger six-coordination metal-organic complexes due to the extra electrostatic interaction between the positively charged central metal cation and the negatively charged vertical ligands. The results also show that the magnitude of the spin-orbit coupling is influenced by the atomic positions of deprotonations of the ligands, and implicitly the direction of the charge transfer between the ligand and the central metal ion.

2.
Molecules ; 25(17)2020 Aug 20.
Artigo em Inglês | MEDLINE | ID: mdl-32825376

RESUMO

The high-yield synthesis and the structural investigation of a new cryptand with C3 symmetry, exhibiting 2,4,6-triphenyl-1,3,5-triazine central units and pyridine-based bridges, are reported. The structure of the compound was investigated by single crystal X-ray diffractometry, NMR (nuclear magnetic resonance), HRMS (high resolution mass spectrometry) measurements, and theoretical calculations. The study of supramolecular behavior in solid state revealed the association of cryptand molecules by C-H---π and π---π contacts. Moreover, theoretical calculations indicated the high binding affinity of the cryptand for various organic molecules as guests.


Assuntos
Éteres Cíclicos/química , Éteres Cíclicos/síntese química , Modelos Moleculares , Piridinas/química , Bases de Schiff/química , Bases de Schiff/síntese química , Cristalografia por Raios X , Espectroscopia de Ressonância Magnética , Estrutura Molecular
3.
Food Funct ; 11(6): 5293-5307, 2020 Jun 24.
Artigo em Inglês | MEDLINE | ID: mdl-32458896

RESUMO

Quercetin, one of the most abundant flavonoids in plant-based foods, commonly occurs in nature in various glycosylated forms. There is still a less explored aspect regarding the cause of diversity of its glycosides, depending on the sugar moiety attached. This work focuses on four wide-spread quercetin glycosides-hyperoside, isoquercitrin, quercitrin and rutin-by testing the property-tuning capacity of different sugar moieties and thus explains and predicts some of their functions in plant-based foods. The electron paramagnetic spectra of the semiquinone anion radicals of these glycosides were interpreted in terms of hyperfine coupling constants and linewidths, highlighting a clear link between spin density trends, the identity of the bound sugar, and their reactivity corroborated with their modelled structures. Redox potential and lipophilicity were connected to a specific flavonoid-enzyme interaction and correlated with their prooxidant reactivity assessed by oxidation of ferrous hemoglobin. Hyperoside and isoquercitin-galactose and glucose glycosides-exhibit the highest prooxidant reactivity owing to their lowest redox potential and lipophilicity whereas rutin and quercitrin-rutinose and rhamnose glycosides-behave vice versa. The ability of the tested glycosides to undergo HAT or SET-type reactions has also been tested using five different analytical assays, including inhibition of cytochrome c-triggered liposome peroxidation. In most cases, rutin proved to be the most unreactive of the four tested glycosides considering either steric or redox reasons whereas the reactivity hierarchy of the other three glycosides were rather assay dependent.


Assuntos
Glicosídeos/química , Quercetina/análogos & derivados , Rutina/química , Antioxidantes/química , Espectroscopia de Ressonância de Spin Eletrônica , Elétrons , Sequestradores de Radicais Livres/química , Hidrogênio/química , Lipídeos/química , Oxidantes/química , Oxirredução , Quercetina/química , Rutina/farmacologia
4.
Molecules ; 25(6)2020 Mar 21.
Artigo em Inglês | MEDLINE | ID: mdl-32245263

RESUMO

2α-Methyl-4,5α-dihydrotestosterone 17ß-propionate, known as drostanolone propionate or masteron, is a synthetic anabolic-androgenic steroid derived from dihydrotestosterone. The crystal structures of two polymorphs of drostanolone propionate have been determined by single crystal X-ray diffraction and both crystallizes in the monoclinic crystal system. One is belonging to the P21 space group, Z = 2, and has one molecule in the asymmetric unit while the second belongs to the I2 space group, Z = 4, and contains two molecules in the asymmetric unit. Another polymorph has been investigated by an X-ray powder diffraction method and solved by Parallel tempering/Monte Carlo technique and refined with the Rietveld method. This polymorph crystallizes in the orthorhombic P212121 space group, Z = 4 having one molecule in the asymmetric unit. The structural configuration analysis shows that the A, B, and C steroid rings exist as chair geometry, while ring D adopts a C13 distorted envelope configuration in all structures. For all polymorphs, the lattice energy has been computed by CLP (Coulomb-London-Pauli), and tight-binding density functional theory methods. Local electron correlation methods were used to estimate the role of electron correlation in the magnitude of the dimer energies. The nature of the intermolecular interactions has been analyzed by the SAPT0 energy decomposition methods as well as by Hirshfeld surfaces.


Assuntos
Androstanóis/química , Cristalização , Ligação de Hidrogênio , Modelos Moleculares , Esteroides/química , Termodinâmica , Difração de Raios X
5.
Molecules ; 24(23)2019 Nov 22.
Artigo em Inglês | MEDLINE | ID: mdl-31766599

RESUMO

The structural stability and photoabsorption properties of Ni(II)-based metal-organic complexes with octahedral coordination having different planar ligand ring structures were investigated employing density functional theory (DFT) and its time-dependent extension (TD-DFT) considering the M06 exchange-correlation functional and the Def2-TZVP basis set. The results showed that the molecular composition of different planar cyclic ligand structures had significant influences on the structural stability and photoabsorption properties of metal-organic complexes. Only those planar ligands that contained aromatic rings met the basic criteria (thermal stability, structural reversibility, and appropriate excitation frequency domain) for light-induced excited spin state trapping, but their spin transition efficiencies were very different. While, in all three aromatic cases, the singlet electronic excitations induced charge distribution that could help in the singlet-to-triplet spin transition, and triplet excitations, which could assist in the backward (triplet-to-singlet) spin transition, was found only for one complex.


Assuntos
Complexos de Coordenação/síntese química , Compostos Macrocíclicos/síntese química , Níquel/química , Simulação por Computador , Complexos de Coordenação/química , Teoria da Densidade Funcional , Ligantes , Compostos Macrocíclicos/química , Modelos Moleculares , Estrutura Molecular , Processos Fotoquímicos , Marcadores de Spin
6.
Molecules ; 24(9)2019 May 10.
Artigo em Inglês | MEDLINE | ID: mdl-31083344

RESUMO

The intermolecular interaction in difluoromethane, dichloromethane, dibromomethane, and diiodomethane dimers has been investigated using high level quantum chemical methods. The potential energy curve of intermolecular interaction along the C⋯C bond distance obtained using the coupled-cluster theory with singles, doubles, and perturbative triples excitations CCSD(T) were compared with values given by the same method, but applying the local (LCCSD(T)) and the explicitly correlated (CCSD(T)-F12) approximations. The accuracy of other theoretical methods-Hartree-Fock (HF), second order Møller-Plesset perturbation (MP2), and dispersion corrected DFT theory-were also presented. In the case of MP2 level, the canonical and the local-correlation cases combined with the density-fitting technique (DF-LMP2)theories were considered, while for the dispersion-corrected DFT, the empirically-corrected BLYP-D and the M06-2Xexchange-correlation functionals were applied. In all cases, the aug-cc-pVTZ basis set was used, and the results were corrected for the basis set superposition error (BSSE) using the counterpoise method. For each molecular system, several dimer geometries were found, and their mutual orientations were compared with the nearest neighbor orientations obtained in recent neutron scattering studies. The nature of the intermolecular interaction energy was discussed.


Assuntos
Compostos Inorgânicos/análise , Compostos Inorgânicos/química , Dimerização , Hidrocarbonetos Bromados/análise , Hidrocarbonetos Bromados/química , Hidrocarbonetos Clorados/análise , Hidrocarbonetos Clorados/química , Hidrocarbonetos Fluorados/análise , Hidrocarbonetos Fluorados/química , Hidrocarbonetos Iodados/análise , Hidrocarbonetos Iodados/química , Modelos Químicos , Modelos Moleculares , Teoria Quântica
7.
Acta Crystallogr C Struct Chem ; 75(Pt 2): 107-119, 2019 02 01.
Artigo em Inglês | MEDLINE | ID: mdl-30720448

RESUMO

Novel cocrystals of promethazine hydrochloride [PTZ-Cl; systematic name: N,N-dimethyl-1-(10H-phenothiazin-10-yl)propan-2-aminium chloride] with succinic acid (PTZ-Cl-succinic, C17H21N2S+·Cl-·0.5C4H6O4), fumaric acid (PTZ-Cl-fumaric, C17H21N2S+·Cl-·0.5C4H4O4) and adipic acid (PTZ-Cl-adipic, C17H21N2S+·Cl-·0.5C6H10O4) were prepared by solvent drop grinding and slow evaporation from acetonitrile solution, along with two oxalic acid cocrystals which were prepared in tetrahydrofuran (the oxalic acid hemisolvate, PTZ-Cl-oxalic, C17H21N2S+·Cl-·0.5C2H2O4) and nitromethane (the hydrogen oxalate salt, PTZ-oxalic, C17H21N2S+·C2HO4-). The crystal structures obtained by crystallization from tetrahydrofuran and acetonitrile include the Cl- ion in the lattice structures, while the Cl- ion is missing from the crystal structure obtained by crystallization from nitromethane (PTZ-oxalic). In order to explain the formation of the two types of supramolecular configurations with oxalic acid, the intermolecular interaction energies were calculated in the presence of the two solvents and the equilibrium configurations were determined using density functional theory (DFT). The cocrystals were studied by X-ray diffraction, IR spectroscopy and differential scanning calorimetry. Additionally, a stability test under special conditions and water solubility were also investigated. PTZ-Cl-succinic, PTZ-Cl-fumaric and PTZ-Cl-adipic crystallized having similar lattice parameter values, and showed a 2:1 PTZ-Cl to dicarboxylic acid stoichiometry. PTZ-Cl-oxalic crystallized in a 2:1 stoichiometric ratio, while the structure lacking the Cl atom belongs has a 1:1 stoichiometry. All the obtained crystals exhibit hydrogen bonds of the type PTZ...Cl...(dicarboxylic acid)...Cl...PTZ, except for PTZ-oxalic, which forms bifurcated bonds between the hydrogen oxalate and promethazinium ions, along with an infinite hydrogen-bonded chain between the hydrogen oxalate anions.

8.
Beilstein J Org Chem ; 14: 1704-1722, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30112076

RESUMO

Background: 4-(n-Octyloxy)aniline is a known component in the elaboration of organic materials with mesogenic properties such as N-substituted Schiff bases, perylene bisimide assemblies with a number of 2-amino-4,6-bis[4-(n-octyloxy)phenylamino]-s-triazines, amphiphilic azobenzene-containing linear-dendritic block copolymers and G-0 monomeric or dimeric dendritic liquid crystals with photochromic azobenzene mesogens. The present ab initio study explores a previously unknown use of 4-(n-octyloxy)aniline in the synthesis, structure and supramolecular behaviour of new dendritic melamines. Results: Starting from 4-(n-octyloxy)aniline, seven G-2 melamine-based dendrimers were obtained in 29-79% overall yields. Their iterative convergent- and chemoselective synthesis consisted of SN2-Ar aminations of cyanuric chloride and final triple N-acylations and Williamson etherifications (→ G-2 covalent trimers) or stoichiometric carboxyl/amino 1:3 neutralisations (→ G-2 ionic trimers). These transformations connected G-1 chloro- and amino-termini dendrons to m-trivalent cores (triazin-2,4,6-triyl and benzene-1,3,5-triyl units) or tripodands (central building blocks), such as N-substituted melamines with 4-hydroxyphenyl or phenyl-4-oxyalkanoic motifs. Owing to the diversity of cores and central building blocks, the structural assortment of the dendritic series was disclosed by solvation effects (affecting reactivity), rotational stereodynamism and self-organisation phenomena (determining a vaulted and/or propeller macromolecular shape in solution). DFT calculations (in solution), (VT) NMR and IR (KBr) spectroscopy supported these assignments. TEM analysis revealed the ability of the title compounds towards self-assembling into homogeneously packed spherical nano-aggregates. Conclusions: The (non)covalent synthesis and step-by-step structural elucidation of novel G-2 melamine dendrimers based on 4-(n-octyloxy)aniline are reported. Our study demonstrates the crucial influence of the nature (covalent vs ionic) of the dendritic construction in tandem with that of its central building blocks on the aptitude of dendrimers to self-organise in solution and to self-assembly in the solid state.

9.
Chemphyschem ; 19(20): 2724-2734, 2018 10 19.
Artigo em Inglês | MEDLINE | ID: mdl-30028068

RESUMO

The processes involved in the photoionization of sodium-doped clusters are complex, not fully understood for many systems and still strongly debated, especially because of the discrepancy between experimental results and predicted cluster structures. We have performed a study on sodium doped formic acid clusters based on UV photoionization spectroscopy and DFT/TDDFT calculations. Apart from the monomer, all the predicted structures show vertical ionization potential values higher than those obtained by the photoionization measurements. We have calculated the absorption spectra and found many Rydberg-like states near the adiabatic ionization potentials and, crucially, in the UV range where the clusters appearance energies fall. This finding supports the hypothesis of adiabatic contributions in the measured ionization potentials for these clusters.

10.
Beilstein J Org Chem ; 14: 1370-1377, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29977401

RESUMO

The aromatic nucleophilic substitution reaction based synthesis of a three-armed cryptand displaying 2,4,6-triphenyl-1,3,5-triazine units as caps and pyridine rings in the bridges, along with NMR, MS and molecular modelling-based structural analysis of this compound are reported. Appropriate NMR and molecular modelling investigations proved the formation of 1:1 host-guest assemblies between the investigated cryptand and some polynuclear aromatic hydrocarbons or their derivatives.

11.
Chem Commun (Camb) ; 52(83): 12322-12325, 2016 Oct 11.
Artigo em Inglês | MEDLINE | ID: mdl-27722565

RESUMO

The formation of highly ordered supramolecular architectures via cooperative C(aliphatic)-H·anion contacts between ß-HCH and various anions (Cl-, Br-, I- and HSO4-) was investigated by single crystal X-ray diffractometry, molecular modelling, ESI-MS and 1H-NMR titrations.

12.
J Mass Spectrom ; 50(10): 1136-43, 2015 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-26456782

RESUMO

Peaks with anomalous abundance found in the mass spectra are associated with ions with enhanced stability. Among the scientific community focused on mass spectrometry, these peaks are called 'magic peaks' and their stability is often because of suggestive symmetric structures. Here, we report findings on ionised Na-acetic acid clusters [Na(+) -(AcA)n ] produced by Na-doping of (AcA)n and UV laser ionisation. Peaks labelled n = 2, 4, 8 are clearly distinguishable in the mass spectra from their anomalous intensity. Ab initio calculations helped elucidate cluster structures and energetic. A plausible interpretation of the magic peaks is given in terms of (AcA)n formed by dimer aggregation. The encasing of Na(+) by twisted dimers is proposed to be the origin of the enhanced cluster stability. A conceivable dimer-formed tube-like closed structure is found for the Na(+) -(AcA)8 .


Assuntos
Ácido Acético/química , Íons/química , Sódio/química , Espectrometria de Massas , Modelos Moleculares
13.
Chemphyschem ; 16(14): 3021-9, 2015 Oct 05.
Artigo em Inglês | MEDLINE | ID: mdl-26296812

RESUMO

The influence of carboxylic acids on water nucleation in the gas phase has been explored in the supersonic expansion of water vapour mixed with acetic acid (AcA) at various concentrations. The sodium-doping method has been used to detect clusters produced in supersonic expansions by using UV photoionisation. The mass spectra obtained at lower acid concentrations show well-detected Na(+) -AcA(H2O)n and Na(+)-AcA2 (H2O)n clusters up to 200 Da and, in the best cooling expansions, emerging Na(+)-AcAm (H2O)n signals at higher masses and unresolved signals that extend beyond m/e values >1000 Da. These signals, which increase with increasing acid content in water vapour, are an indication that the cluster growth taking place arises from mixed water-acid clusters. Theoretical calculations show that small acid-water clusters are stable and their formation is even thermodynamically favoured with respect to pure water clusters, especially at lower temperatures. These findings suggest that acetic acid may play a significant role as a pre-nucleation embryo in the formation of aerosols in wet environments.

14.
Phys Chem Chem Phys ; 17(8): 5861-71, 2015 Feb 28.
Artigo em Inglês | MEDLINE | ID: mdl-25631256

RESUMO

The fully propagated real time-dependent density functional theory method has been applied to study the laser-molecule interaction in 5- and 6-benzyluracil (5BU and 6BU). The molecular geometry optimization and the time-dependent electronic dynamics propagation were carried out using the M11-L local meta-NGA (nonseparable gradient approximations) exchange-correlation functional together with the def2-TZVP basis set. Different laser field parameters like direction, strength, and wavelength have been varied in order to estimate the conditions for an efficient excitation of the molecules. The results show that the two molecules respond differently to the applied laser field and therefore specific laser field parameters have to be chosen for each of them in order to get efficient and selective excitation behavior. It was also found that from the molecular excitation point of view not only the magnitude of the transition dipoles between the involved orbitals but also their orientation with respect to the laser field is important. On the other hand, it was shown that the molecular excitation is a very complex overlapping of different one-electron orbital depopulation-population processes of the occupied and virtual orbitals.


Assuntos
Modelos Moleculares , Uracila/análogos & derivados , Elétrons , Lasers , Teoria Quântica , Termodinâmica , Uracila/química
15.
J Mass Spectrom ; 49(8): 700-8, 2014 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-25044897

RESUMO

Understanding the gas-phase chemistry of acetaldehyde can be challenging because the molecule can assume several tautomeric forms, namely keto, enol and carbene. The two last forms are the most stable ionic forms. Here, insight into the gas-phase cluster ion chemistry of homogeneous acetaldehyde and mixed water-acetaldehyde clusters is provided by mass spectrometry/vacuum ultraviolet photoionization combined with density functional theory calculations. (AA)nH(+) clusters (AA = acetaldehyde) and mixed (AA)nH3O(+) clusters were detected using tunable vacuum ultraviolet photoionization. Barrierless proton transfers were observed during the geometry optimization of the most stable dimer structures and helped to explain the cluster ion chemistry induced by photoionization, namely the formation of deprotonated tautomers and protonated keto tautomers. Water was found to catalyze the keto-enol and keto-carbene isomerizations and facilitate the proton transfer from the ionized enol or carbene part of the cluster to the neutral keto part, resulting in protonated keto structures. The production of protonated keto structures was identified to be the main fragmentation channel following ionization of the homogeneous acetaldehyde cluster and a channel for ionized mixed clusters as well. These findings are significant for a broad range of fields, including current atmospheric models, because acetaldehyde is one of the most prominent organic species in the troposphere and ions play a crucial role in aerosol formation.

16.
J Mol Model ; 20(3): 2113, 2014 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-24567152

RESUMO

The theoretical IR and Raman spectra of the guanine-cytosine DNA base pairs in Watson-Crick and Hoogsteen configurations were computed using DFT method with M06-2X meta-hybrid GGA exchange-correlation functional, including the anharmonic corrections and solvent effects. The results for harmonic frequencies and their anharmonic corrections were compared with our previously calculated values obtained with the B3PW91 hybrid GGA functional. Significant differences were obtained for the anharmonic corrections calculated with the two different DFT functionals, especially for the stretching modes, while the corresponding harmonic frequencies did not differ considerable. For the Hoogtseen case the H⁺ vibration between the G-C base pair can be characterized as an asymmetric Duffing oscillator and therefore unrealistic anharmonic corrections for normal modes where this proton vibration is involved have been obtained. The spectral modification due to the anharmonic corrections, solvent effects and the influence of sugar-phosphate group for the Watson-Crick and Hoogsteen base pair configurations, respectively, were also discussed. For the Watson-Crick case also the influence of the stacking interaction on the theoretical IR and Raman spectra was analyzed. Including the anharmonic correction in our normal mode analysis is essential if one wants to obtain correct assignments of the theoretical frequency values as compared with the experimental spectra.


Assuntos
Pareamento de Bases , Citosina/química , Guanina/química , Modelos Moleculares , Análise Espectral/métodos , Estrutura Molecular , Solventes/química , Espectrofotometria Infravermelho , Análise Espectral Raman , Vibração
17.
Langmuir ; 29(33): 10539-48, 2013 Aug 20.
Artigo em Inglês | MEDLINE | ID: mdl-23875692

RESUMO

Polydopamine (PDA) formed by the oxidation of dopamine is an important polymer, in particular, for coating various surfaces. It is composed of dihydroxyindole, indoledione, and dopamine units, which are assumed to be covalently linked. Although PDA has been applied in a manifold way, its structure is still under discussion. Similarities have been observed in melanins/eumelanins as naturally occurring, deeply colored polymer pigments derived from L-DOPA. Recently, an alternative structure was proposed for PDA wherein dihydroxyindoline, indolinedione, and eventually dopamine units are not covalently linked to each other but are held together by hydrogen bonding between oxygen atoms or π stacking. In this study, we show that this structural proposal is very unlikely to occur taking into account unambiguous results obtained by different analytical methods, among them (13)C CPPI MAS NMR (cross-polarization polarization-inversion magic angle spinning NMR), (1)H MAS NMR (magic angle spinning NMR), and ES-HRMS (electrospray ionization high-resolution mass spectrometry) for the first time in addition to XPS (X-ray photoelectron spectroscopy) and FTIR spectroscopy. The results give rise to a verified structural assignment of PDA wherein dihydroxyindole and indoledione units with different degrees of (un)saturation are covalently linked by C-C bonds between their benzene rings. Furthermore, proof of open-chain (dopamine) monomer units in PDA is provided. Advanced DFT calculations imply the arrangements of several PDA chains preferably by quinone-hydroquinone-type interactions in a parallel or antiparallel manner. From all of these results, a number of hypotheses published before could be experimentally supported or were found to be contradictory, thus leading to a better understanding of the PDA structure.


Assuntos
Indóis/química , Polímeros/química , Espectroscopia de Ressonância Magnética , Espectroscopia Fotoeletrônica
18.
Phys Chem Chem Phys ; 15(19): 7161-73, 2013 May 21.
Artigo em Inglês | MEDLINE | ID: mdl-23558515

RESUMO

A numerical study is reported concerning the first and second singlet excited-states of 5-benzyluracil using the multireference self-consistent field (state-averaged CASSCF) method. The vertical excitation energies of low-lying excited-states were characterized using the SA-CASSCF method, as well as using higher-level methods, such as CASPT2, MRCI and EOM-CCSD. The local minima and conical intersections found on the potential energy surfaces (PESs) were characterized in terms of molecular geometry and natural population analysis. Different relaxation pathways on the PESs are identified and discussed by comparing with the similar pathways found for the individual monomers of uracil and benzene. The molecule can be thought of as a model system for the study of crosslink reaction between DNA and proteins induced by UV light.


Assuntos
Benzeno/química , Uracila/análogos & derivados , Uracila/química , Modelos Moleculares , Teoria Quântica , Termodinâmica
19.
Acta Chim Slov ; 59(1): 18-23, 2012 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-24061168

RESUMO

In this paper the procedure for the preparation of inclusion compounds of bioactive substance 2-[(2-aminoetoxy)-methyl]-4-(2-chlorophenyl)-1,4-dihydro-6-methyl-3,5-pyridine dicarboxylic acid 3-ethyl-5-methyl esterbenzene sulfonate, called amlodipine besylate with ß-cyclodextrin (ß-CD) and their structural characterization was described. Molecular inclusion compound of amlodipine besylate is obtained by different preparation method: kneading, co-precipitation and freeze-drying. The so obtained compounds were investigated by FTIR spectroscopy, X-ray diffraction method and differential scanning calorimetric measurements (DSC) to evidence their formation. Molecular modeling (using DFT theoretical computations) shows the spatial architecture of the inclusion compound in good agreement with FTIR experimental data: the drug is included with dihydropyridine dicarboxylate part inside ß-cyclodextrin cavity. The inclusion of amlodipine besylate in ß-cyclodextrin increases the stability and bioavailability of the drug.

20.
Int J Mol Sci ; 12(5): 3102-16, 2011.
Artigo em Inglês | MEDLINE | ID: mdl-21686172

RESUMO

The study aims to present a detailed theoretical investigation of noncovalent intermolecular interactions between different π-π stacking nitrogen substituted phenothiazine derivatives by applying second-order Møller-Plesset perturbation (MP2), density functional (DFT) and semiempirical theories. The conformational stability of these molecular systems is mainly given by the dispersion-type electron correlation effects. The density functional tight-binding (DFTB) method applied for dimer structures are compared with the results obtained by the higher level theoretical methods. Additionally, the optimal configuration of the investigated supramolecular systems and their self-assembling properties are discussed.


Assuntos
Modelos Moleculares , Nitrogênio/química , Fenotiazinas/química , Simulação por Computador , Conformação Molecular
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