Szczepan Roszak - Academia.edu (original) (raw)
Papers by Szczepan Roszak
The Li + CationThe Descendant of H + or an Ancestor of Na + ? The Properties of Li + Ar n ( n = 1−6) Clusters
The Journal of Physical Chemistry A, 2004
Ab initio studies of molecular structures and properties of the Li + Ar n complexes were carried ... more Ab initio studies of molecular structures and properties of the Li + Ar n complexes were carried out. The investigation of the Li + Ar dimer with the MP2(FULL)/6-31 1G+(3df) method provides satisfactory agreement with the available experimental data. This conclusion is extrapolated for larger Li + Ar n (n > 1) clusters which are studied within this level of theory. The reported complexes are stable and deserve the future experimental efforts. The obtained results indicate that the consecutive complexes represent the most symmetrical structures possible with the closing shell for the Li + Ar 6 cation. The dissociation energies as well as interaction energy components follow systematic paths of changes. The reveled clusters are different from their H + Ar n predecessors characterized by two solvation shells of 7 ligands total and are also different from Na + Ar n clusters for which the single shell may accommodate eight argons. The Ar-Ar interactions do not influence geometries of small complexes but are noticeable in larger structures due to repulsive forces caused by the lack of space around the central cation.
Relativistic Symmetries in the Electronic Structure and Properties of Molecules
Relativistic Methods for Chemists, 2010
ABSTRACT
Structure and properties of the low-lying electronic states of CeC[sub 2] and CeC[sub 2][sup +]
The Journal of Chemical Physics, 2007
Theoretical studies on the electronic and thermodynamic properties of several electronic states o... more Theoretical studies on the electronic and thermodynamic properties of several electronic states of CeC(2) and CeC(2)(+) have been carried out employing state-of-the-art single- and multireference techniques. The ground and the low-lying electronic states of these two species have been found to possess C(2v) triangular structures. A (3)B(2) state has been found to be the ground state of CeC(2) while for CeC(2)(+) (2)A(2) is the ground state. The computed electron ionization energy is in excellent agreement with experiment. The experimentally observed thermodynamic properties (dissociation and atomization energies) of reactions involving CeC(2) dissociation are corrected using the computed gas-phase properties of the molecule and the partition functions. The bent triplet and singlet state of CeC(2) exhibit large dipole moments (7.0-10.5 D) and it is consistent with the ionic character (through dative charge transfer) of the cluster in ground and excited states.
Advances in In Silico Research on Nerve Agents
Practical Aspects of Computational Chemistry III, 2014
ABSTRACT Nerve-agents (NAs) are toxic environment contaminants causing massive health hazard to t... more ABSTRACT Nerve-agents (NAs) are toxic environment contaminants causing massive health hazard to the plant, animal, and civilian populations. Moreover, these materials have the properties of adsorption on various artificial surfaces which include cement, paints, metal oxides and clay minerals. These adsorption properties also threaten long-lasting toxic after-effects of NA exposure to the environment. Modeling these diverse NA-exposure characteristics through computational techniques has been always of great importance because of the restrictions in using such materials directly in the experiments due to their high toxicity. The present review discusses the recent advancements in the in silico research of NA, which include their conformational, biological and surface-occlusion properties. There are some positive sides of NA-adsorption also. The adsorption properties of NAs on oxide surfaces are used as binder to remove and subsequently deactivate them through chemical treatments. Moreover, NA adsorption on various surfaces is also useful to design materials to detect those agents using spectroscopic techniques. The present review also discusses the theoretical advancements in these directions in details. All of these discussions are mostly based on the results of the state of the art quantum-chemical computations. Related experimental results are also discussed to validate the results from such theoretical approaches.
On the weak intermolecular interactions and their influence on the optical properties of unsaturated hydrocarbons. Part 1: Two-body interactions†
Molecular Physics, 2006
The systematic ab initio studies of intermolecular interaction energy components in the model uns... more The systematic ab initio studies of intermolecular interaction energy components in the model unsaturated hydrocarbon complexes have been performed. The influence of the weak intermolecular interactions on the optical properties has been analyzed within the supermolecular approach. The estimated interaction energy components and electric properties of the studied systems indicate the substantial influence of the intermolecular forces on the optical
The Li + CationThe Descendant of H + or an Ancestor of Na + ? The Properties of Li + Ar n ( n = 1−6) Clusters
The Journal of Physical Chemistry A, 2004
Theoretical ab initio study on the electronic states of GaO and Ga2O
Potential energy curves have been calculated for the ground and excited doublet and quartet state... more Potential energy curves have been calculated for the ground and excited doublet and quartet states of the radical gallium monoxide. The ground state, X2Σ+, is found to have a minimum at 1.65Å with a well-depth of 4.65eV, while the lowest excited state, A2Π is found to lie very close to the ground state, at ν00 of 4204 cm−1 with rmin
Polyhedron, 2000
New cis-and trans-nitrosyl complexes of the formula M(NO) 2 (O 2 CR) 2 (M= Cr and Mo) were synthe... more New cis-and trans-nitrosyl complexes of the formula M(NO) 2 (O 2 CR) 2 (M= Cr and Mo) were synthesized and characterized spectroscopically. The supporting theoretical studies indicate the deviation of molecules from their ideal geometries. The most striking consequence is the deformation of the ON M NO fragment from its linear form, in trans complexes. This deformation leads to the additional weak w s (NO) vibration.
Quantum Chemical Studies of Neutral and Ionized DyX, DyX2, and DyX3 Species (X = F, Cl, Br, I) and the Implications for the Mass Spectra of Gaseous DyX3
European Journal of Inorganic Chemistry, 2004
ABSTRACT The mass spectrum pattern of DyF3(g) and the appearance potentials for identified ions w... more ABSTRACT The mass spectrum pattern of DyF3(g) and the appearance potentials for identified ions were measured and compared with the respective data obtained previously for DyCl3, DyBr3, and DyI3. The structural parameters, total energies, and vibrational frequencies of DyX3, DyX2, and DyX (X = F, Cl, Br, I) neutral and single ionized species were determined by quantum-chemical studies. The theoretical appearance potentials of different ions, calculated from energies of gaseous species, are in the good agreement with the experimental data. Fragmentation energies of the DyXn+ ion, where n = 1, 2, 3, were computed and compared with the mass spectra patterns of the respective vapour species. A theoretical electron population analysis indicates the involvement of the s and f valence electrons of Dy in the bond formation as well as in the ionization processes. The σ-back donation from halogen atoms to the dysprosium center partially compensates the electron density loss. The ionization strengthens the bonding in the DyX and DyX2 molecules. The ionization of DyX3 destroys the C3v symmetrical structure due to the Jahn−Teller effect. Contrary to the other studied systems, the open shell character of DyX3+ arises not only from unpaired electrons of dysprosium but also from electron density on halogen atoms. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Binding in clusters with closed-subshell atoms (alkaline-earth elements)
Advances in Quantum Chemistry, 2001
... 277 [30] Gaussian 98, Revision A.6, MJ Frisch, GW Trucks, HB Schlegel, GE Scuseria, MA Robb, ... more ... 277 [30] Gaussian 98, Revision A.6, MJ Frisch, GW Trucks, HB Schlegel, GE Scuseria, MA Robb, JR Cheeseman, VG Zakrzewski, JA Mont-gomery, Jr ... Gill, B. Johon-son, W. Chen, MW Wong, JL Andres, C. Gonzalez, M. Head-Gordon, [31] FW Biegler-KSnig, RFW Bager, and TH ...
The Journal of Physical Chemistry C, 2010
The foreign atom doping influences the properties of carbon materials, and it is a possible way o... more The foreign atom doping influences the properties of carbon materials, and it is a possible way of designing materials of desired characteristics. Density functional calculations have been carried out on various isomers of boron-doped (4,0) and (9,0) carbon nanotubes as templates to investigate the doping effect on the structure and electronic properties on such systems. The results indicate that these boron-doped carbon nanotubes show local structural changes, mostly due to the elongation of bonds. The insertion of heteroatoms perturbs the π-conjugation system, which, in effect, destabilizes the material through higher energy cost of formation. The position of the foreign atom controls the new organization of electron density and leads to one of two possible distributions, viz., global (where electron density is distributed over the molecular surface) or local (localized distribution of electron density). This feature, in turn, can influence the bonding of the reactants while interacting with the surface. The charge distribution at a particular boron-doped site always possesses the local characteristics with a positively charged boron atom surrounded by negatively charged carbons. Such a character is also a measure of the driving force for influencing the substitution reaction in the vicinity of boron through an ionic mechanism.
The Journal of Physical Chemistry B, 2006
Interaction energies have been estimated between sarin and a model enzyme cavity of acetylcholine... more Interaction energies have been estimated between sarin and a model enzyme cavity of acetylcholinesterase (ACHE) using the density functional and Møller-Plesset second-order perturbation (MP2) levels of theories. The calculated interaction energies have been compared with those of acetylcholine and the same model ACHE cavity. The ACHE‚‚‚sarin and ACHE‚‚‚acetylcholine (Ach) structures have been optimized using DFT based two-layer ONIOM hybrid calculations. The nature of interactions has been investigated in detail using an interaction energy partitioning technique. The effects of solvation on the interaction energies have also been taken into account. An inhibition mechanism during the uptake of sarin inside the ACHE cavity has been proposed from the comparison of the energetics of the ACHE‚‚‚sarin and ACHE‚‚‚Ach complexes.
The Journal of Physical Chemistry B, 2005
DFT-based molecular dynamics and quantum chemistry theory approaches are combined to investigate ... more DFT-based molecular dynamics and quantum chemistry theory approaches are combined to investigate the various conformers of sarin-serine adduct. Twenty different conformers have been located as the local minima on the potential energy surface. They are categorized into five classes based on the relative orientation of sarin moiety. The energy properties of the twenty sarin-serine conformers revealed in the present study suggest that at least four of the conformers (1-1, 4-1, 4-2, and 5-1) are expected to have crucial contributions to the phosphonylation and dealkylation reactions of the sarin-serine adduct at low temperature. Among them, the 1-1 conformer which has both the lowest energy and the highest Boltzman distribution relative probability is expected to be the most important. However, as the temperature rises, the 4-1 conformer plays a more important role than 1-1 in the sarin-serine adductation reactions. Under the relatively high temperatures, the contribution of conformer 5-1 decreases in the phosphonylation and dealkylation reactions while at least eight other conformers (1-2, 1-3, 3-1, 3-4, 3-7, 4-2, 4-3, and 4-4) are expected to have larger contributions in these reactions.
Theoretical Studies of Symmetric Five-Membered Heterocycle Derivatives of Carbazole and Fluorene: Precursors of Conducting Polymers
The Journal of Physical Chemistry A, 2006
Structures, electron ionization and excitation energies, and electron density distribution are st... more Structures, electron ionization and excitation energies, and electron density distribution are studied for carbazole and fluorene derivatives substituted symmetrically by thiophene, ethylenodioxythiophene, furane, or pyrrole. The calculated properties of the molecules directly or indirectly mimic molecular parameters that are important for the design of processes of polymerization or for modeling the final polymer. The studies have been focused on the variation in the properties as a function of the chemical composition of the central fragment and the external rings. The calculated properties of consecutive oligomers indicate their fast convergence to values characterizing polymers.
The Journal of Physical Chemistry A, 2004
Dimeric gaseous species Sn 2 Br x I 4-x , x ) 0-4, were detected by Knudsen effusion mass spectro... more Dimeric gaseous species Sn 2 Br x I 4-x , x ) 0-4, were detected by Knudsen effusion mass spectrometry. Fragment ionic species Sn 2 Br y I 3-y + , y ) 0-3, yielded by electron bombardment were identified in mass spectra of SnBr 2 -SnI 2 equilibrium vapors. The structure and bonding of identified ions and neutral precursors were studied by quantum-chemical methods. Enthalpies and entropies of the anion-exchange reactions involving gaseous dimeric species were estimated by the use of mass spectrometric and theoretical data. Implications of the thermodynamic and structural data obtained by theoretical methods on the observed fragmentation paths of the neutral Sn 2 Br x I 4-x species are discussed. The nature of interactions leading to dimer formation is studied on the basis of the atomic charge distribution and the variational-perturbational interaction energy decomposition scheme. The studies unravelled the additivity of properties such as bond length, vibrational frequencies, and atomic charge distribution corresponding to Sn-Br and Sn-I bonds participating in studied molecules and ions.
The Journal of Physical Chemistry A, 2006
Theoretical Thermodynamics and the Nature of Interactions of the Quasi-Binary NaCl−SnCl 2 System
The Journal of Physical Chemistry A, 2006
The formation of NaSnX(3) (X = halogen) influences the sodium concentration in metal halide lamps... more The formation of NaSnX(3) (X = halogen) influences the sodium concentration in metal halide lamps making the thermodynamics of such reactions critical for technological developments. Theoretical predictions of the structure and vibrational properties of the quasi-binary NaCl-SnCl(2) system lead to thermodynamical data determined through the third law evaluation. Ab initio enthalpy and entropy of dissociation of NaSnCl(3) also is reported. Additionally, insight into the nature of chemical bonding is provided by electron population analysis and the interaction energy decomposition scheme.
Theoretical Studies on the Mechanism of C−P Bond Cleavage of a Model α-Aminophosphonate in Acidic Condition †
The Journal of Physical Chemistry A, 2008
Various reaction paths of the P-C bond cleavage of alpha-aminophosphonates in acidic media, resul... more Various reaction paths of the P-C bond cleavage of alpha-aminophosphonates in acidic media, resulting in the derivatives of phosphonic acid, has been investigated using density functional level of theories in the gas phase as well as in aqueous medium. Dimethyl (alpha-anilinobenzyl)phosphonate has been used as the model molecule and our investigation confirms a three steps process including protonation, P-C bond cleavage, and the transformation of the products from the final transition state (imine cation and H-phosphonate) through hydrolysis. The most favorable reaction path starts from the amino group protonation, followed by a proton transfer through N-H...O(P) hydrogen bond, and the P-C bond cleavage from the resulting protonated structure. Explicit inclusion of water molecules indicated that two waters are needed for the P-C bond cleavage, and the calculated mechanistic paths in this hydrated model are similar to those of the aqueous solvation model.
The chemistry of lithium-modified carbonium cations
Molecular Physics, 2005
The existence of CH4Li(H2)n (n = 0–9) and CH4LiHLi(H2)n (n = 0–13) complexes is predicted. The de... more The existence of CH4Li(H2)n (n = 0–9) and CH4LiHLi(H2)n (n = 0–13) complexes is predicted. The determined molecular structures are significantly different from their parent carbonium clusters. The formation of clusters is principally based on the consecutive filling of shells governed by Li centres. The shell characterized by weaker CH···H2 interactions also exists in the vicinity of the CH4 fragment. The dissociation energies and
Structures and energetics of extended proton-bound N 2 H + –He n ( n =1–17) complexes
Molecular Physics, 2005
The series of proton-bound N2HHen (n=1–17) complexes was studied by ab initio methods for the fir... more The series of proton-bound N2HHen (n=1–17) complexes was studied by ab initio methods for the first time. The structures of cations are based on the consecutive filling of five ligand shells. The capacity of the shells located on planes perpendicular to the N2H axes amounts to five. Shells are well separated in space, and the pattern of changes of the
The Li + CationThe Descendant of H + or an Ancestor of Na + ? The Properties of Li + Ar n ( n = 1−6) Clusters
The Journal of Physical Chemistry A, 2004
Ab initio studies of molecular structures and properties of the Li + Ar n complexes were carried ... more Ab initio studies of molecular structures and properties of the Li + Ar n complexes were carried out. The investigation of the Li + Ar dimer with the MP2(FULL)/6-31 1G+(3df) method provides satisfactory agreement with the available experimental data. This conclusion is extrapolated for larger Li + Ar n (n > 1) clusters which are studied within this level of theory. The reported complexes are stable and deserve the future experimental efforts. The obtained results indicate that the consecutive complexes represent the most symmetrical structures possible with the closing shell for the Li + Ar 6 cation. The dissociation energies as well as interaction energy components follow systematic paths of changes. The reveled clusters are different from their H + Ar n predecessors characterized by two solvation shells of 7 ligands total and are also different from Na + Ar n clusters for which the single shell may accommodate eight argons. The Ar-Ar interactions do not influence geometries of small complexes but are noticeable in larger structures due to repulsive forces caused by the lack of space around the central cation.
Relativistic Symmetries in the Electronic Structure and Properties of Molecules
Relativistic Methods for Chemists, 2010
ABSTRACT
Structure and properties of the low-lying electronic states of CeC[sub 2] and CeC[sub 2][sup +]
The Journal of Chemical Physics, 2007
Theoretical studies on the electronic and thermodynamic properties of several electronic states o... more Theoretical studies on the electronic and thermodynamic properties of several electronic states of CeC(2) and CeC(2)(+) have been carried out employing state-of-the-art single- and multireference techniques. The ground and the low-lying electronic states of these two species have been found to possess C(2v) triangular structures. A (3)B(2) state has been found to be the ground state of CeC(2) while for CeC(2)(+) (2)A(2) is the ground state. The computed electron ionization energy is in excellent agreement with experiment. The experimentally observed thermodynamic properties (dissociation and atomization energies) of reactions involving CeC(2) dissociation are corrected using the computed gas-phase properties of the molecule and the partition functions. The bent triplet and singlet state of CeC(2) exhibit large dipole moments (7.0-10.5 D) and it is consistent with the ionic character (through dative charge transfer) of the cluster in ground and excited states.
Advances in In Silico Research on Nerve Agents
Practical Aspects of Computational Chemistry III, 2014
ABSTRACT Nerve-agents (NAs) are toxic environment contaminants causing massive health hazard to t... more ABSTRACT Nerve-agents (NAs) are toxic environment contaminants causing massive health hazard to the plant, animal, and civilian populations. Moreover, these materials have the properties of adsorption on various artificial surfaces which include cement, paints, metal oxides and clay minerals. These adsorption properties also threaten long-lasting toxic after-effects of NA exposure to the environment. Modeling these diverse NA-exposure characteristics through computational techniques has been always of great importance because of the restrictions in using such materials directly in the experiments due to their high toxicity. The present review discusses the recent advancements in the in silico research of NA, which include their conformational, biological and surface-occlusion properties. There are some positive sides of NA-adsorption also. The adsorption properties of NAs on oxide surfaces are used as binder to remove and subsequently deactivate them through chemical treatments. Moreover, NA adsorption on various surfaces is also useful to design materials to detect those agents using spectroscopic techniques. The present review also discusses the theoretical advancements in these directions in details. All of these discussions are mostly based on the results of the state of the art quantum-chemical computations. Related experimental results are also discussed to validate the results from such theoretical approaches.
On the weak intermolecular interactions and their influence on the optical properties of unsaturated hydrocarbons. Part 1: Two-body interactions†
Molecular Physics, 2006
The systematic ab initio studies of intermolecular interaction energy components in the model uns... more The systematic ab initio studies of intermolecular interaction energy components in the model unsaturated hydrocarbon complexes have been performed. The influence of the weak intermolecular interactions on the optical properties has been analyzed within the supermolecular approach. The estimated interaction energy components and electric properties of the studied systems indicate the substantial influence of the intermolecular forces on the optical
The Li + CationThe Descendant of H + or an Ancestor of Na + ? The Properties of Li + Ar n ( n = 1−6) Clusters
The Journal of Physical Chemistry A, 2004
Theoretical ab initio study on the electronic states of GaO and Ga2O
Potential energy curves have been calculated for the ground and excited doublet and quartet state... more Potential energy curves have been calculated for the ground and excited doublet and quartet states of the radical gallium monoxide. The ground state, X2Σ+, is found to have a minimum at 1.65Å with a well-depth of 4.65eV, while the lowest excited state, A2Π is found to lie very close to the ground state, at ν00 of 4204 cm−1 with rmin
Polyhedron, 2000
New cis-and trans-nitrosyl complexes of the formula M(NO) 2 (O 2 CR) 2 (M= Cr and Mo) were synthe... more New cis-and trans-nitrosyl complexes of the formula M(NO) 2 (O 2 CR) 2 (M= Cr and Mo) were synthesized and characterized spectroscopically. The supporting theoretical studies indicate the deviation of molecules from their ideal geometries. The most striking consequence is the deformation of the ON M NO fragment from its linear form, in trans complexes. This deformation leads to the additional weak w s (NO) vibration.
Quantum Chemical Studies of Neutral and Ionized DyX, DyX2, and DyX3 Species (X = F, Cl, Br, I) and the Implications for the Mass Spectra of Gaseous DyX3
European Journal of Inorganic Chemistry, 2004
ABSTRACT The mass spectrum pattern of DyF3(g) and the appearance potentials for identified ions w... more ABSTRACT The mass spectrum pattern of DyF3(g) and the appearance potentials for identified ions were measured and compared with the respective data obtained previously for DyCl3, DyBr3, and DyI3. The structural parameters, total energies, and vibrational frequencies of DyX3, DyX2, and DyX (X = F, Cl, Br, I) neutral and single ionized species were determined by quantum-chemical studies. The theoretical appearance potentials of different ions, calculated from energies of gaseous species, are in the good agreement with the experimental data. Fragmentation energies of the DyXn+ ion, where n = 1, 2, 3, were computed and compared with the mass spectra patterns of the respective vapour species. A theoretical electron population analysis indicates the involvement of the s and f valence electrons of Dy in the bond formation as well as in the ionization processes. The σ-back donation from halogen atoms to the dysprosium center partially compensates the electron density loss. The ionization strengthens the bonding in the DyX and DyX2 molecules. The ionization of DyX3 destroys the C3v symmetrical structure due to the Jahn−Teller effect. Contrary to the other studied systems, the open shell character of DyX3+ arises not only from unpaired electrons of dysprosium but also from electron density on halogen atoms. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Binding in clusters with closed-subshell atoms (alkaline-earth elements)
Advances in Quantum Chemistry, 2001
... 277 [30] Gaussian 98, Revision A.6, MJ Frisch, GW Trucks, HB Schlegel, GE Scuseria, MA Robb, ... more ... 277 [30] Gaussian 98, Revision A.6, MJ Frisch, GW Trucks, HB Schlegel, GE Scuseria, MA Robb, JR Cheeseman, VG Zakrzewski, JA Mont-gomery, Jr ... Gill, B. Johon-son, W. Chen, MW Wong, JL Andres, C. Gonzalez, M. Head-Gordon, [31] FW Biegler-KSnig, RFW Bager, and TH ...
The Journal of Physical Chemistry C, 2010
The foreign atom doping influences the properties of carbon materials, and it is a possible way o... more The foreign atom doping influences the properties of carbon materials, and it is a possible way of designing materials of desired characteristics. Density functional calculations have been carried out on various isomers of boron-doped (4,0) and (9,0) carbon nanotubes as templates to investigate the doping effect on the structure and electronic properties on such systems. The results indicate that these boron-doped carbon nanotubes show local structural changes, mostly due to the elongation of bonds. The insertion of heteroatoms perturbs the π-conjugation system, which, in effect, destabilizes the material through higher energy cost of formation. The position of the foreign atom controls the new organization of electron density and leads to one of two possible distributions, viz., global (where electron density is distributed over the molecular surface) or local (localized distribution of electron density). This feature, in turn, can influence the bonding of the reactants while interacting with the surface. The charge distribution at a particular boron-doped site always possesses the local characteristics with a positively charged boron atom surrounded by negatively charged carbons. Such a character is also a measure of the driving force for influencing the substitution reaction in the vicinity of boron through an ionic mechanism.
The Journal of Physical Chemistry B, 2006
Interaction energies have been estimated between sarin and a model enzyme cavity of acetylcholine... more Interaction energies have been estimated between sarin and a model enzyme cavity of acetylcholinesterase (ACHE) using the density functional and Møller-Plesset second-order perturbation (MP2) levels of theories. The calculated interaction energies have been compared with those of acetylcholine and the same model ACHE cavity. The ACHE‚‚‚sarin and ACHE‚‚‚acetylcholine (Ach) structures have been optimized using DFT based two-layer ONIOM hybrid calculations. The nature of interactions has been investigated in detail using an interaction energy partitioning technique. The effects of solvation on the interaction energies have also been taken into account. An inhibition mechanism during the uptake of sarin inside the ACHE cavity has been proposed from the comparison of the energetics of the ACHE‚‚‚sarin and ACHE‚‚‚Ach complexes.
The Journal of Physical Chemistry B, 2005
DFT-based molecular dynamics and quantum chemistry theory approaches are combined to investigate ... more DFT-based molecular dynamics and quantum chemistry theory approaches are combined to investigate the various conformers of sarin-serine adduct. Twenty different conformers have been located as the local minima on the potential energy surface. They are categorized into five classes based on the relative orientation of sarin moiety. The energy properties of the twenty sarin-serine conformers revealed in the present study suggest that at least four of the conformers (1-1, 4-1, 4-2, and 5-1) are expected to have crucial contributions to the phosphonylation and dealkylation reactions of the sarin-serine adduct at low temperature. Among them, the 1-1 conformer which has both the lowest energy and the highest Boltzman distribution relative probability is expected to be the most important. However, as the temperature rises, the 4-1 conformer plays a more important role than 1-1 in the sarin-serine adductation reactions. Under the relatively high temperatures, the contribution of conformer 5-1 decreases in the phosphonylation and dealkylation reactions while at least eight other conformers (1-2, 1-3, 3-1, 3-4, 3-7, 4-2, 4-3, and 4-4) are expected to have larger contributions in these reactions.
Theoretical Studies of Symmetric Five-Membered Heterocycle Derivatives of Carbazole and Fluorene: Precursors of Conducting Polymers
The Journal of Physical Chemistry A, 2006
Structures, electron ionization and excitation energies, and electron density distribution are st... more Structures, electron ionization and excitation energies, and electron density distribution are studied for carbazole and fluorene derivatives substituted symmetrically by thiophene, ethylenodioxythiophene, furane, or pyrrole. The calculated properties of the molecules directly or indirectly mimic molecular parameters that are important for the design of processes of polymerization or for modeling the final polymer. The studies have been focused on the variation in the properties as a function of the chemical composition of the central fragment and the external rings. The calculated properties of consecutive oligomers indicate their fast convergence to values characterizing polymers.
The Journal of Physical Chemistry A, 2004
Dimeric gaseous species Sn 2 Br x I 4-x , x ) 0-4, were detected by Knudsen effusion mass spectro... more Dimeric gaseous species Sn 2 Br x I 4-x , x ) 0-4, were detected by Knudsen effusion mass spectrometry. Fragment ionic species Sn 2 Br y I 3-y + , y ) 0-3, yielded by electron bombardment were identified in mass spectra of SnBr 2 -SnI 2 equilibrium vapors. The structure and bonding of identified ions and neutral precursors were studied by quantum-chemical methods. Enthalpies and entropies of the anion-exchange reactions involving gaseous dimeric species were estimated by the use of mass spectrometric and theoretical data. Implications of the thermodynamic and structural data obtained by theoretical methods on the observed fragmentation paths of the neutral Sn 2 Br x I 4-x species are discussed. The nature of interactions leading to dimer formation is studied on the basis of the atomic charge distribution and the variational-perturbational interaction energy decomposition scheme. The studies unravelled the additivity of properties such as bond length, vibrational frequencies, and atomic charge distribution corresponding to Sn-Br and Sn-I bonds participating in studied molecules and ions.
The Journal of Physical Chemistry A, 2006
Theoretical Thermodynamics and the Nature of Interactions of the Quasi-Binary NaCl−SnCl 2 System
The Journal of Physical Chemistry A, 2006
The formation of NaSnX(3) (X = halogen) influences the sodium concentration in metal halide lamps... more The formation of NaSnX(3) (X = halogen) influences the sodium concentration in metal halide lamps making the thermodynamics of such reactions critical for technological developments. Theoretical predictions of the structure and vibrational properties of the quasi-binary NaCl-SnCl(2) system lead to thermodynamical data determined through the third law evaluation. Ab initio enthalpy and entropy of dissociation of NaSnCl(3) also is reported. Additionally, insight into the nature of chemical bonding is provided by electron population analysis and the interaction energy decomposition scheme.
Theoretical Studies on the Mechanism of C−P Bond Cleavage of a Model α-Aminophosphonate in Acidic Condition †
The Journal of Physical Chemistry A, 2008
Various reaction paths of the P-C bond cleavage of alpha-aminophosphonates in acidic media, resul... more Various reaction paths of the P-C bond cleavage of alpha-aminophosphonates in acidic media, resulting in the derivatives of phosphonic acid, has been investigated using density functional level of theories in the gas phase as well as in aqueous medium. Dimethyl (alpha-anilinobenzyl)phosphonate has been used as the model molecule and our investigation confirms a three steps process including protonation, P-C bond cleavage, and the transformation of the products from the final transition state (imine cation and H-phosphonate) through hydrolysis. The most favorable reaction path starts from the amino group protonation, followed by a proton transfer through N-H...O(P) hydrogen bond, and the P-C bond cleavage from the resulting protonated structure. Explicit inclusion of water molecules indicated that two waters are needed for the P-C bond cleavage, and the calculated mechanistic paths in this hydrated model are similar to those of the aqueous solvation model.
The chemistry of lithium-modified carbonium cations
Molecular Physics, 2005
The existence of CH4Li(H2)n (n = 0–9) and CH4LiHLi(H2)n (n = 0–13) complexes is predicted. The de... more The existence of CH4Li(H2)n (n = 0–9) and CH4LiHLi(H2)n (n = 0–13) complexes is predicted. The determined molecular structures are significantly different from their parent carbonium clusters. The formation of clusters is principally based on the consecutive filling of shells governed by Li centres. The shell characterized by weaker CH···H2 interactions also exists in the vicinity of the CH4 fragment. The dissociation energies and
Structures and energetics of extended proton-bound N 2 H + –He n ( n =1–17) complexes
Molecular Physics, 2005
The series of proton-bound N2HHen (n=1–17) complexes was studied by ab initio methods for the fir... more The series of proton-bound N2HHen (n=1–17) complexes was studied by ab initio methods for the first time. The structures of cations are based on the consecutive filling of five ligand shells. The capacity of the shells located on planes perpendicular to the N2H axes amounts to five. Shells are well separated in space, and the pattern of changes of the