The formation of highly ordered supramolecular architectures via cooperative C(aliphatic)-H·anion... more The formation of highly ordered supramolecular architectures via cooperative C(aliphatic)-H·anion contacts between β-HCH and various anions (Cl(-), Br(-), I(-) and HSO4(-)) was investigated by single crystal X-ray diffractometry, molecular modelling, ESI-MS and (1)H-NMR titrations.
ABSTRACT 1. A kémiai Hamilton operátor közelítés (CHA, chemical Hamiltonian approach) keretén bel... more ABSTRACT 1. A kémiai Hamilton operátor közelítés (CHA, chemical Hamiltonian approach) keretén belül módszert fejlesztettünk ki molekulák erőállandóinak és rezgési frekvenciáinak számítására. A kifejlesztett módszert alkalmaztuk hidrogénhidas molekulakomplexekre. 2. Elektronkorreláció számítására alkalmas módszer kifejlesztése és alkalmazása a CHA elmélet keretein belül. 3. Új típusú komplex és imaginárius elnyelő potenciálok kifejlesztése és ezek összehasonlítása. 4. Számos molekuláris rendszer nem adiabatikus tulajdonságait vizsgáltuk a nem adiabatikus csatolási mátrixok segítségével. | 1. Applying the chemical Hamiltonian approach a method has been developed to calculate the force constants and harmonical vibrational frequencies in molecules. This method has been used to study hydrogen-bonded molecular complexes. 2. Using the CHA framework electron correlation method has been developed and applied to study the electronic structure of different molecules. 3. New types of complex and imaginary absorbing potentials have been developed and compared. 4. The non-adiabatic behaviour of several molecular systems have been studied using the non-adiabatic coupling matrices.
Fullerenes Nanotubes and Carbon Nanostructures, 2010
Design of diamond-like lattices can be achieved by using some net operations. Hypothetical networ... more Design of diamond-like lattices can be achieved by using some net operations. Hypothetical networks, thus obtained, can be characterized in their topology by various counting polynomials and topological indices from which they are derived. The repeat units of the proposed network are derived from adamantane, the constructive unit of diamond, and proved to be extremely stable, as shown by computed total energy. Their topology is described in terms of Omega polynomial.
Equilibrium geometries of methylene chloride dimers have been calculated using the local version ... more Equilibrium geometries of methylene chloride dimers have been calculated using the local version of second order Møller-Plesset perturbation theory (LMP2), combined with the density fitting (DF) technique. Five distinct energy minimum bonded conformations have been resolved. The results have been compared to the intramolecular geometries and the intermolecular orientational correlations obtained previously from neutron and X-ray scattering experiments combined with molecular dynamics and reverse Monte Carlo modeling.
In this paper the procedure for the preparation of inclusion compounds of bioactive substance 2-[... more 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 β-cyclodextrin (β-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 β-cyclodextrin cavity. The inclusion of amlodipine besylate in β-cyclodextrin increases the stability and bioavailability of the drug.
The formation and high stability of the H-bond-driven supramolecular architectures of the syn and... more The formation and high stability of the H-bond-driven supramolecular architectures of the syn and anti isomers of the dioxime of bicyclo[3.3.1]nonane-3,7-dione were investigated by single crystal X-ray diffraction, NMR, FTIR, and molecular modeling. Self-assembly of the achiral syn isomer into a cyclic trimer (supramolecular wheel) and of the chiral anti isomer into homochiral cyclic dimers was observed.
Langmuir the Acs Journal of Surfaces and Colloids, Jul 22, 2013
Polydopamine (PDA) formed by the oxidation of dopamine is an important polymer, in particular, fo... more 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.
Using the HF + MP2 methods with full geometry optimizations the charge transfer (CT) from the PO4... more Using the HF + MP2 methods with full geometry optimizations the charge transfer (CT) from the PO4- groups of DNA to the arginine or lysine side chains of the proteins forming the nuclohistone cores were calculated. (X-ray investigation shows that in the nucleohistone core there are eight histones which are wrapped around by a DNA superhelix). We have found 0.21e and 0.26e CT, respectively. Knowing the structure of nucleohistones one can estimate a charge transfer at every fourth base pair. Taking as average 0.10e CT (there are also other attractive interactions) one can compute the concentrations of holes in DNA. From these one can obtain the dc conductivity for polyguanilic acid (the mobilities are known).
The influence of carboxylic acids on water nucleation in the gas phase has been explored in the s... more 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(H2 O)n and Na(+) AcA2 (H2 O)n clusters up to 200 Da and, in the best cooling expansions, emerging Na(+) AcAm (H2 O)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.
ABSTRACT The solid state physical approach is widely used for the characterization of electronic ... more ABSTRACT The solid state physical approach is widely used for the characterization of electronic properties of DNA. In the simplest case the helical symmetry is explicitly utilized with a repeat unit containing only a single nucleotide or nucleotide pair. This model provides a band structure that is easily interpretable and reflects the main characteristic features of the single nucleotide or a nucleotide pair chain, respectively. The chemical variability of the different DNA chains is, however, almost completely neglected in this way. In the present work we have investigated the effect of the different sequences on the band structure of periodic DNA models. For this purpose we have applied the Hartree-Fock crystal orbital method for single and double stranded DNA chains with two different subsequent nucleotides in the repeat unit of former and two different nucleotide pairs in the latter case, respectively. These results are compared to simple helical models with uniform sequences. The valence and conduction bands related to the stacked nucleotide bases of single stranded DNA built up only from guanidine as well as of double stranded DNA built up only from guanidine-cytidine pairs showed special properties different from the other cases. Namely, larger conduction and lower valence band positions and this way larger band gaps and smaller widths of these bands. With the introduction of non-uniform sequences containing guanidine became more similar to each other and to the other ones. The maximal band widths of the non-uniform sequences are considerably smaller than in the case of uniform sequences implying smaller charge carrier mobilities both in the conduction and valence bands.
ABSTRACT Theoretical investigations have been performed for unit systems with Ni(II) and Zn(II) c... more ABSTRACT Theoretical investigations have been performed for unit systems with Ni(II) and Zn(II) coordination between azorubine and 1,4,8,11-tetraazacyclotetradecane (cyclam) complexes using the conventional DFT and the DFT-based tight binding (DFTB) methods. Two different geometries (short and long) and spin states (singlet and triplet) of the model system built by two mesylate groups and the cyclam ring together with Ni(II) and Zn(II) ions were energetically characterized. For the Ni(II) coordination complex the triplet geometry is preferred, but one could not exclude also the presence of the singlet spin configuration due to the huge energy barrier defined by the intersystem crossing. The intersystem crossing geometry of the singlet-triplet transition was studied in details and the corresponding spin-orbit couplings were discussed. For the Zn(II) coordination complex only the singlet state was found. Polymer chain build up from four unit systems presents irregular forms with strong coordination bonds between units.
ABSTRACT Fullerene aggregation can follow a well-defined geometry of which energy trends to a min... more ABSTRACT Fullerene aggregation can follow a well-defined geometry of which energy trends to a minimal value. The pattern of space filling differs function of the dimensions and shapes of composing small fullerenes. An attempt of building and stability evaluation of several fullerene aggregates was made. The results show these aggregates as multi-shell covalently bonded structures with a stability comparable to that of C60, the reference fullerene in nanoscience. The calculations were made at the DFTB+ level of theory.
Physical chemistry chemical physics : PCCP, Jan 28, 2015
The fully propagated real time-dependent density functional theory method has been applied to stu... more 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 wi...
Understanding the gas-phase chemistry of acetaldehyde can be challenging because the molecule can... more 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 carben...
In this paper the procedure for the preparation of inclusion compounds of bioactive substance 2-[... more 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 β-cyclodextrin (β-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 β-cyclodextrin cavity. The inclusion of amlodipine besylate in β-cyclodextrin increases the stability and bio...
ABSTRACT Carbon allotropes, including triple-, double-, and single periodic, and finite non-perio... more ABSTRACT Carbon allotropes, including triple-, double-, and single periodic, and finite non-periodic, nanostructures have been designed by using map operations and their topological and energetic properties studied. Two allotropes of the diamond D5 are discussed in this chapter: the dense hyper-diamond, with an “anti”-diamantane structure, and a quasi-diamond, which is a five-fold symmetry quasicrystal with “syn”-diamantane structure. Some substructures of these allotropes are proposed as possible intermediates in the synthesis of some hyper-graphenes and their energetics evaluated at Hartree-Fock, DFT (B3LYP) and DFTB levels of theory. A topological description of D5_anti network and derived hyper-graphenes, in terms of the net parameter and Omega polynomial, is also given.
The formation of highly ordered supramolecular architectures via cooperative C(aliphatic)-H·anion... more The formation of highly ordered supramolecular architectures via cooperative C(aliphatic)-H·anion contacts between β-HCH and various anions (Cl(-), Br(-), I(-) and HSO4(-)) was investigated by single crystal X-ray diffractometry, molecular modelling, ESI-MS and (1)H-NMR titrations.
ABSTRACT 1. A kémiai Hamilton operátor közelítés (CHA, chemical Hamiltonian approach) keretén bel... more ABSTRACT 1. A kémiai Hamilton operátor közelítés (CHA, chemical Hamiltonian approach) keretén belül módszert fejlesztettünk ki molekulák erőállandóinak és rezgési frekvenciáinak számítására. A kifejlesztett módszert alkalmaztuk hidrogénhidas molekulakomplexekre. 2. Elektronkorreláció számítására alkalmas módszer kifejlesztése és alkalmazása a CHA elmélet keretein belül. 3. Új típusú komplex és imaginárius elnyelő potenciálok kifejlesztése és ezek összehasonlítása. 4. Számos molekuláris rendszer nem adiabatikus tulajdonságait vizsgáltuk a nem adiabatikus csatolási mátrixok segítségével. | 1. Applying the chemical Hamiltonian approach a method has been developed to calculate the force constants and harmonical vibrational frequencies in molecules. This method has been used to study hydrogen-bonded molecular complexes. 2. Using the CHA framework electron correlation method has been developed and applied to study the electronic structure of different molecules. 3. New types of complex and imaginary absorbing potentials have been developed and compared. 4. The non-adiabatic behaviour of several molecular systems have been studied using the non-adiabatic coupling matrices.
Fullerenes Nanotubes and Carbon Nanostructures, 2010
Design of diamond-like lattices can be achieved by using some net operations. Hypothetical networ... more Design of diamond-like lattices can be achieved by using some net operations. Hypothetical networks, thus obtained, can be characterized in their topology by various counting polynomials and topological indices from which they are derived. The repeat units of the proposed network are derived from adamantane, the constructive unit of diamond, and proved to be extremely stable, as shown by computed total energy. Their topology is described in terms of Omega polynomial.
Equilibrium geometries of methylene chloride dimers have been calculated using the local version ... more Equilibrium geometries of methylene chloride dimers have been calculated using the local version of second order Møller-Plesset perturbation theory (LMP2), combined with the density fitting (DF) technique. Five distinct energy minimum bonded conformations have been resolved. The results have been compared to the intramolecular geometries and the intermolecular orientational correlations obtained previously from neutron and X-ray scattering experiments combined with molecular dynamics and reverse Monte Carlo modeling.
In this paper the procedure for the preparation of inclusion compounds of bioactive substance 2-[... more 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 β-cyclodextrin (β-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 β-cyclodextrin cavity. The inclusion of amlodipine besylate in β-cyclodextrin increases the stability and bioavailability of the drug.
The formation and high stability of the H-bond-driven supramolecular architectures of the syn and... more The formation and high stability of the H-bond-driven supramolecular architectures of the syn and anti isomers of the dioxime of bicyclo[3.3.1]nonane-3,7-dione were investigated by single crystal X-ray diffraction, NMR, FTIR, and molecular modeling. Self-assembly of the achiral syn isomer into a cyclic trimer (supramolecular wheel) and of the chiral anti isomer into homochiral cyclic dimers was observed.
Langmuir the Acs Journal of Surfaces and Colloids, Jul 22, 2013
Polydopamine (PDA) formed by the oxidation of dopamine is an important polymer, in particular, fo... more 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.
Using the HF + MP2 methods with full geometry optimizations the charge transfer (CT) from the PO4... more Using the HF + MP2 methods with full geometry optimizations the charge transfer (CT) from the PO4- groups of DNA to the arginine or lysine side chains of the proteins forming the nuclohistone cores were calculated. (X-ray investigation shows that in the nucleohistone core there are eight histones which are wrapped around by a DNA superhelix). We have found 0.21e and 0.26e CT, respectively. Knowing the structure of nucleohistones one can estimate a charge transfer at every fourth base pair. Taking as average 0.10e CT (there are also other attractive interactions) one can compute the concentrations of holes in DNA. From these one can obtain the dc conductivity for polyguanilic acid (the mobilities are known).
The influence of carboxylic acids on water nucleation in the gas phase has been explored in the s... more 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(H2 O)n and Na(+) AcA2 (H2 O)n clusters up to 200 Da and, in the best cooling expansions, emerging Na(+) AcAm (H2 O)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.
ABSTRACT The solid state physical approach is widely used for the characterization of electronic ... more ABSTRACT The solid state physical approach is widely used for the characterization of electronic properties of DNA. In the simplest case the helical symmetry is explicitly utilized with a repeat unit containing only a single nucleotide or nucleotide pair. This model provides a band structure that is easily interpretable and reflects the main characteristic features of the single nucleotide or a nucleotide pair chain, respectively. The chemical variability of the different DNA chains is, however, almost completely neglected in this way. In the present work we have investigated the effect of the different sequences on the band structure of periodic DNA models. For this purpose we have applied the Hartree-Fock crystal orbital method for single and double stranded DNA chains with two different subsequent nucleotides in the repeat unit of former and two different nucleotide pairs in the latter case, respectively. These results are compared to simple helical models with uniform sequences. The valence and conduction bands related to the stacked nucleotide bases of single stranded DNA built up only from guanidine as well as of double stranded DNA built up only from guanidine-cytidine pairs showed special properties different from the other cases. Namely, larger conduction and lower valence band positions and this way larger band gaps and smaller widths of these bands. With the introduction of non-uniform sequences containing guanidine became more similar to each other and to the other ones. The maximal band widths of the non-uniform sequences are considerably smaller than in the case of uniform sequences implying smaller charge carrier mobilities both in the conduction and valence bands.
ABSTRACT Theoretical investigations have been performed for unit systems with Ni(II) and Zn(II) c... more ABSTRACT Theoretical investigations have been performed for unit systems with Ni(II) and Zn(II) coordination between azorubine and 1,4,8,11-tetraazacyclotetradecane (cyclam) complexes using the conventional DFT and the DFT-based tight binding (DFTB) methods. Two different geometries (short and long) and spin states (singlet and triplet) of the model system built by two mesylate groups and the cyclam ring together with Ni(II) and Zn(II) ions were energetically characterized. For the Ni(II) coordination complex the triplet geometry is preferred, but one could not exclude also the presence of the singlet spin configuration due to the huge energy barrier defined by the intersystem crossing. The intersystem crossing geometry of the singlet-triplet transition was studied in details and the corresponding spin-orbit couplings were discussed. For the Zn(II) coordination complex only the singlet state was found. Polymer chain build up from four unit systems presents irregular forms with strong coordination bonds between units.
ABSTRACT Fullerene aggregation can follow a well-defined geometry of which energy trends to a min... more ABSTRACT Fullerene aggregation can follow a well-defined geometry of which energy trends to a minimal value. The pattern of space filling differs function of the dimensions and shapes of composing small fullerenes. An attempt of building and stability evaluation of several fullerene aggregates was made. The results show these aggregates as multi-shell covalently bonded structures with a stability comparable to that of C60, the reference fullerene in nanoscience. The calculations were made at the DFTB+ level of theory.
Physical chemistry chemical physics : PCCP, Jan 28, 2015
The fully propagated real time-dependent density functional theory method has been applied to stu... more 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 wi...
Understanding the gas-phase chemistry of acetaldehyde can be challenging because the molecule can... more 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 carben...
In this paper the procedure for the preparation of inclusion compounds of bioactive substance 2-[... more 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 β-cyclodextrin (β-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 β-cyclodextrin cavity. The inclusion of amlodipine besylate in β-cyclodextrin increases the stability and bio...
ABSTRACT Carbon allotropes, including triple-, double-, and single periodic, and finite non-perio... more ABSTRACT Carbon allotropes, including triple-, double-, and single periodic, and finite non-periodic, nanostructures have been designed by using map operations and their topological and energetic properties studied. Two allotropes of the diamond D5 are discussed in this chapter: the dense hyper-diamond, with an “anti”-diamantane structure, and a quasi-diamond, which is a five-fold symmetry quasicrystal with “syn”-diamantane structure. Some substructures of these allotropes are proposed as possible intermediates in the synthesis of some hyper-graphenes and their energetics evaluated at Hartree-Fock, DFT (B3LYP) and DFTB levels of theory. A topological description of D5_anti network and derived hyper-graphenes, in terms of the net parameter and Omega polynomial, is also given.
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