The geometry and the spectroscopic properties of (HCl)2 have been calculated at the SCF level. A ... more The geometry and the spectroscopic properties of (HCl)2 have been calculated at the SCF level. A nearly orthogonal dimer with an almost linear H bridge has been found. The optimized Cl–Cl distance is Re = 7.48 a.u., while Cl–H bond lengths are found to be r1 = 2.4133 and r2 = 2.4075 a.u. for the proton donor and acceptor monomeric units, respectively. The binding energy corrected for basis set superposition error is computed to be B = 3.61 kcal/mol. The spectroscopic properties (force constants, dipole and quadrupole moment derivatives) of monomeric units as a part of (HCl)2 are discussed.
The paper collects the answers of the authors to the following questions: Is the lack of precisio... more The paper collects the answers of the authors to the following questions: Is the lack of precision in the definition of many chemical concepts one of the reasons for the coexistence of many partition schemes? Does the adoption of a given partition scheme imply a set of more precise definitions of the underlying chemical concepts? How can one use the results of a partition scheme to improve the clarity of definitions of concepts? Are partition schemes subject to scientific Darwinism? If so, what is the influence of a community's sociological pressure in the “natural selection” process? To what extent does/can/should investigated systems influence the choice of a particular partition scheme? Do we need more focused chemical validation of Energy Decomposition Analysis (EDA) methodology and descriptors/terms in general? Is there any interest in developing common benchmarks and test sets for cross‐validation of methods? Is it possible to contemplate a unified partition scheme (let us...
The reaction mechanism of electrophilic substitution by chlorine on the benzene derivative (anili... more The reaction mechanism of electrophilic substitution by chlorine on the benzene derivative (aniline) catalyzed by aluminium chloride has been studied theoretically by DFT (Density Functional Theory) calculations by taking CCSD(T) as reference method. The results obtained in the gas phase are consistent with the traditional description of this reaction: the orientation of the chlorination of aniline depends on the stability of a reaction intermediate (Wheland said). Taking out of consideration the reactants and products, four stationary points have been found in the potential surface energy of the reaction
The geometric parameters of stationary points on the potential surface energy of the chlorination... more The geometric parameters of stationary points on the potential surface energy of the chlorination reaction of nitrobenzene in the presence of Aluminium chloride as catalyst were investigated theoretically by hybrid DFT (Density Functional Theory) calculations in order to determine his general reaction mechanism in gas phase and in solution. The results obtained by DFT have been compared with CCSD(T) method which is the most powerful post-Hartree Fock method in terms of inclusion of dynamic correlation. Although the electrophilic substitution reaction is widely taught in most courses in organic chemistry, the mechanism has been very few studied theoretically. The results obtained in gas phase are consistent with the traditional description of these reactions: the orientation of this substitution in meta position depends on the stability of a reaction intermediate (Wheland said). Without taking in consideration the reactants and products, six stationary points are found on the potenti...
complementary because each of them partially addresses the question. However, other answers can b... more complementary because each of them partially addresses the question. However, other answers can be given. For instance, one can object that bottles being made to store liquid food (wine, beer), coloured glass is chosen mostly because it prevents sunlight to downgrade the antioxidants and therefore increases the storage life. 1 The answer given by the chemist explicitly invokes the chemical composition of the glass used to make bottles and for this reason it should be referred to as a chemical explanation. Chemical explanations are grounded on the knowledge of Chemistry. Chemical explanations of the structure of the matter rely on a picture in which elemental atoms are linked by bonds. Bonding interactions are moreover ruled by the location of the constituting elements in the periodic table. Chemical explanations often make use concepts proper to Chemistry, such as those of bond, lone pair, valence,..., which have been criticized as lacking of scientific content or have not enough precise or inconsistent definitions. (cf. R. Thom in Paraboles et Catastrophes [2]), We are often faced to a demarcation problem: to what extend chemical explanations are scientific explanations or in other words what are the requirements which must be fulfilled to make a chemical explanation a scientific explanation. Therefore, explanations have to be critically analysed from different epistemological viewpoints such as Duhemian conventionalism and methodological falsificationism. We must also be conscious that chemical explanations may have different structures: for example the occurrence of an event can be deduced from a set of true Abstract Some of the opinions I have on the description of the structure of the matter in chemistry. Keywords Representation of the matter • Lewis's model • VSEPR • Epistemology Published as part of the special collection of articles "First European Symposium on Chemical Bonding".
Applications of Topological Methods in Molecular Chemistry, 2016
Though almost a century old, Lewis’s theory of chemical bonding remains at the heart of the under... more Though almost a century old, Lewis’s theory of chemical bonding remains at the heart of the understanding of chemical structure. In spite of their basic discrete nature, Lewis’s structures (topological 0-manifolds) continue to lend themselves to sophisticated treatments leading to valuable results in terms of topological analysis of chemical properties. The bonding topology is however not only defined, but also refined by direct consideration of the nuclear geometry, itself determined by the configuration of the embedding electron cloud. During the last century, the theory has thus been complemented by the mesomery concept, by the Linnett’s double quartet scheme and by the VSEPR/LCP models. These models rely on an assumed spatial disposition of the electrons which does not take the quantum mechanical aspects into account. These models are reexamined by investigation of the topological 1-manifolds generated by the gradient field of potential functions featuring the electron cloud configuration, such as the electron density or electron localization function (ELF). In this chapter, we reexamine these models in order to escape from the quantum mechanical dilemma and we show how topological analyzes enable to recover these models.
A series of pseudopotential periodic Hartree-Fock calculations has been performed on a V[sub 2]O[... more A series of pseudopotential periodic Hartree-Fock calculations has been performed on a V[sub 2]O[sub 5] crystal. The optimized V-O bond lengths and stretching force constants are found to be in good agreement with experiment. The band structure and density of states are reported, and in contrast with tight-binding calculations there is no gap in the valence band. From the projected density of state it is shown that the V atom d orbitals play an important role in the bonding and therefore that this oxide is partially ionic. Three types of V-O bonds are recognized in this structure: The mainly covalent vanadyl bond, the ionic bond connecting the central vanadium to the chain oxygen, and the electrostatic-van der Waals bond which ensures the stacking of the layers. 29 refs., 9 figs., 3 tabs.
The bonding in KgInll and RbgInl1 has been investigated at the SCF level with the periodic Hartre... more The bonding in KgInll and RbgInl1 has been investigated at the SCF level with the periodic Hartree-Fock method. Comparison is made with In11 clusters with formal charges 7and 8calculated at the same level. The structure of the 7cluster has been optimized; it significantly differs from the structure observed in the condensed phase. The second anion (8-) is found to be dissociative. Moreover, the indium Mulliken populations in clusters are dramatically different from those calculated for the solid phase. This indicates that the reliability of the cluster approach is highly questionable. The stability of the solid phases is mostly due to the electrostatic interactions between the anionic clusters and the alkali counterions. The integrated charge density in the cation region is consistent with a picture in which an electron is delocalized over the potassium layers. The band structure and density of states of the solid phases are discussed. Both &Inll and Rb81nl1 are found to be weak electronic conductors. At the present state of the art, it is not possible to assess the charge borne by the indium cluster and, therefore, to decide whether one or more electrons are delocalized over potassium layers. The bonding in these systems has been investigated from the topological analysis of the electron localization function point of view. The bonding in the In11 anionic clusters is characterized by a network of attractors lying 1 A outward from the indium centers.
An electron localization function and catastrophe theory analysis on the molecular mechanism of g... more An electron localization function and catastrophe theory analysis on the molecular mechanism of gas-phase
The electron localization function (ELF) approach to chemical bonding is revisited as a tool to c... more The electron localization function (ELF) approach to chemical bonding is revisited as a tool to check the falsifiability of the Lewis hypotheses. It is shown that the boundaries of the ELF basins correspond to zero-flux surfaces of the local integrated same spin pair probability enabling the determination of regions of the molecular space which maximizes the opposite spin pair density and therefore groups of electrons. The ELF yields a partition into core and valence basins which matches the Lewis model. The valence basins which correspond either to electron lone pairs or to bonds enable the definition of atomic valence shells in which bonding basins are shared by at least two atomic valence shells. The ELF basin populations take into account the mesomery which explains the deviations from ideal values. The organization of the basins around the atomic cores often complies with the VSEPR rules. The behavior of the ELF basins upon deformation of the nuclear frame sheds light onto the reactivity and reaction mechanisms, whereas the basin compressibilities provide chemical explanations of pressure-induced phase transitions.
The journal of physical chemistry. B, Jan 29, 2009
We present a novel quantitative strategy for monitoring chemical bonding transformations in solid... more We present a novel quantitative strategy for monitoring chemical bonding transformations in solids from the topology of their electronic structure. Developed in the context of the electron localization function formalism, it provides an unambiguous characterization of long-range interactions and bond formation. Charge flux between electron localization regions is found to hold the key for identifying the nature of the interaction between the chemically meaningful entities in the solid (valence shells, lone pairs, molecules, etc.). Because of the wide range of interesting properties that high pressure induces in molecular solids, we illustrate the potentialities of our strategy to unveil controversial questions involved in the bond reorganization along the polymerization of CO2. Our study confirms that the topology of the bonding network in the pseudopolymeric phases points toward the incipient formation of the new bonds in the higher pressure polymers. This transformation is identif...
Accurate electron densities and related functions are sources of chemical information enabling th... more Accurate electron densities and related functions are sources of chemical information enabling the understanding of the structure and chemical properties of molecules and solids. The quantum mechanical backgrounds of the electron probability distribution functions (the electron density and the pair functions), of the electron localization function (ELF), of the source function, and of some other related local descriptors of the electron distribution and of its properties are presented in the first part of this chapter. The rough data provided by these functions do not always reveal all of the expected chemical information, such as the characterization of bonding properties, and, therefore, methodological bridges are necessary to recover the phenomenological chemical concepts. The chapter is focused on the topological approaches that provide a description in the position space consistent with the Lewis structures and with the valence shell electron pair repulsion model. The theory of dynamical systems, applied to the gradient field of the electron density and of the ELF, is the most used mathematical tool enabling a rigorous partition of the space into basins of attractors that are chemically significant and also to propose criteria for a qualitative characterization of the bonding interactions and of their evolution during a chemical reaction. A deep quantitative insight is further achieved by integrating the one particle and pair densities as well as other density of property functions over the basin volumes. The statistical analysis of the variance and covariance of the basin populations provide a measure of the electron delocalization. The use of these techniques of analysis of the electron density properties is illustrated by a series of examples belonging to the field of inorganic chemistry.
Physics of the Earth and Planetary Interiors, 1992
The periodic Hartree-Fock method has been used to sample the potential energy hypersurface of CaO... more The periodic Hartree-Fock method has been used to sample the potential energy hypersurface of CaO to determine a collective reaction pathway between the low-pressure (NaCI) and high-pressure (CsCl) phases. The predicted transition pressure, 68 GPa, is in good agreement with both experimental data and previous theoretical studies. At low pressure the enthalpy (E + P1") surface presents only one minimum corresponding to the Bi (NaCl) structure. A second minimum appears at the B2 (CsCI) geometry when the pressure is increased. The transformation kinetics is estimated using the Johnson-Mehl model coupled to random nucleation and interface-controlled growth. Independently of the interfacial energy, the kinetics is highly pressure dependent. A pressure hysteresis loop is predicted. The results presented are in qualitative agreement with available data.
DFT calculations using the B3LYP functional are reported for a model of the (oxy)tyrosinase activ... more DFT calculations using the B3LYP functional are reported for a model of the (oxy)tyrosinase active site including the two copper cations, six imidazoles and dioxygen (in the oxy form), plus either phenol (taken as a model of tyrosine, the enzyme's natural substrate) or 2-aminophenol, a very efficient inhibitor. The results obtained suggest that (i) both the substrate and the inhibitor have to be deprotonated to form a stable complex with the model of the '' native '' form of the enzyme; (ii) only phenol binds to the oxy form; (iii) the complex formed between our oxy model and 2-aminophenate is more stable than that with phenate, suggesting a competitive inhibition mechanism between the deprotonated forms of the substrate and of the inhibitor.
... Isabelle Fourré,; Bernard Silvi,; Patrick Chaquin,; Alain Sevin. Article first published onli... more ... Isabelle Fourré,; Bernard Silvi,; Patrick Chaquin,; Alain Sevin. Article first published online: 21 MAY 1999. ... Keywords: carbonyl and imine compounds; excitation; electron attachment; ionization; electron localization function; bonding analysis. Abstract. ...
What is a local viewpoint of delocalized bonds? We try to provide an answer to this paradoxical q... more What is a local viewpoint of delocalized bonds? We try to provide an answer to this paradoxical question by investigating representative conjugated organic molecules (namely, allyl cation, trans-butadiene, and benzene) together with reference nonconjugated systems (ethylene and propene) by means of topological analysis of the electron localization function ELF. The valence attractors of the ELF gradient field are classified according to their synaptic order (i.e., connections with core attractors). The basin populations [Formula: see text] (i.e., the integrated density over the attractor basins) and their standard deviation, σ, have been calculated and are discussed. The basin populations and their relative fluctuations, defined as [Formula: see text] are sensitive criteria of delocalization. In the case of well-localized C—C or C=C bonds, λ ~0.4, whereas for delocalized bonds λ increases to about 0.5. Another criterion of delocalization is provided by the basin hierarchy, which is ...
The geometry and the spectroscopic properties of (HCl)2 have been calculated at the SCF level. A ... more The geometry and the spectroscopic properties of (HCl)2 have been calculated at the SCF level. A nearly orthogonal dimer with an almost linear H bridge has been found. The optimized Cl–Cl distance is Re = 7.48 a.u., while Cl–H bond lengths are found to be r1 = 2.4133 and r2 = 2.4075 a.u. for the proton donor and acceptor monomeric units, respectively. The binding energy corrected for basis set superposition error is computed to be B = 3.61 kcal/mol. The spectroscopic properties (force constants, dipole and quadrupole moment derivatives) of monomeric units as a part of (HCl)2 are discussed.
The paper collects the answers of the authors to the following questions: Is the lack of precisio... more The paper collects the answers of the authors to the following questions: Is the lack of precision in the definition of many chemical concepts one of the reasons for the coexistence of many partition schemes? Does the adoption of a given partition scheme imply a set of more precise definitions of the underlying chemical concepts? How can one use the results of a partition scheme to improve the clarity of definitions of concepts? Are partition schemes subject to scientific Darwinism? If so, what is the influence of a community's sociological pressure in the “natural selection” process? To what extent does/can/should investigated systems influence the choice of a particular partition scheme? Do we need more focused chemical validation of Energy Decomposition Analysis (EDA) methodology and descriptors/terms in general? Is there any interest in developing common benchmarks and test sets for cross‐validation of methods? Is it possible to contemplate a unified partition scheme (let us...
The reaction mechanism of electrophilic substitution by chlorine on the benzene derivative (anili... more The reaction mechanism of electrophilic substitution by chlorine on the benzene derivative (aniline) catalyzed by aluminium chloride has been studied theoretically by DFT (Density Functional Theory) calculations by taking CCSD(T) as reference method. The results obtained in the gas phase are consistent with the traditional description of this reaction: the orientation of the chlorination of aniline depends on the stability of a reaction intermediate (Wheland said). Taking out of consideration the reactants and products, four stationary points have been found in the potential surface energy of the reaction
The geometric parameters of stationary points on the potential surface energy of the chlorination... more The geometric parameters of stationary points on the potential surface energy of the chlorination reaction of nitrobenzene in the presence of Aluminium chloride as catalyst were investigated theoretically by hybrid DFT (Density Functional Theory) calculations in order to determine his general reaction mechanism in gas phase and in solution. The results obtained by DFT have been compared with CCSD(T) method which is the most powerful post-Hartree Fock method in terms of inclusion of dynamic correlation. Although the electrophilic substitution reaction is widely taught in most courses in organic chemistry, the mechanism has been very few studied theoretically. The results obtained in gas phase are consistent with the traditional description of these reactions: the orientation of this substitution in meta position depends on the stability of a reaction intermediate (Wheland said). Without taking in consideration the reactants and products, six stationary points are found on the potenti...
complementary because each of them partially addresses the question. However, other answers can b... more complementary because each of them partially addresses the question. However, other answers can be given. For instance, one can object that bottles being made to store liquid food (wine, beer), coloured glass is chosen mostly because it prevents sunlight to downgrade the antioxidants and therefore increases the storage life. 1 The answer given by the chemist explicitly invokes the chemical composition of the glass used to make bottles and for this reason it should be referred to as a chemical explanation. Chemical explanations are grounded on the knowledge of Chemistry. Chemical explanations of the structure of the matter rely on a picture in which elemental atoms are linked by bonds. Bonding interactions are moreover ruled by the location of the constituting elements in the periodic table. Chemical explanations often make use concepts proper to Chemistry, such as those of bond, lone pair, valence,..., which have been criticized as lacking of scientific content or have not enough precise or inconsistent definitions. (cf. R. Thom in Paraboles et Catastrophes [2]), We are often faced to a demarcation problem: to what extend chemical explanations are scientific explanations or in other words what are the requirements which must be fulfilled to make a chemical explanation a scientific explanation. Therefore, explanations have to be critically analysed from different epistemological viewpoints such as Duhemian conventionalism and methodological falsificationism. We must also be conscious that chemical explanations may have different structures: for example the occurrence of an event can be deduced from a set of true Abstract Some of the opinions I have on the description of the structure of the matter in chemistry. Keywords Representation of the matter • Lewis's model • VSEPR • Epistemology Published as part of the special collection of articles "First European Symposium on Chemical Bonding".
Applications of Topological Methods in Molecular Chemistry, 2016
Though almost a century old, Lewis’s theory of chemical bonding remains at the heart of the under... more Though almost a century old, Lewis’s theory of chemical bonding remains at the heart of the understanding of chemical structure. In spite of their basic discrete nature, Lewis’s structures (topological 0-manifolds) continue to lend themselves to sophisticated treatments leading to valuable results in terms of topological analysis of chemical properties. The bonding topology is however not only defined, but also refined by direct consideration of the nuclear geometry, itself determined by the configuration of the embedding electron cloud. During the last century, the theory has thus been complemented by the mesomery concept, by the Linnett’s double quartet scheme and by the VSEPR/LCP models. These models rely on an assumed spatial disposition of the electrons which does not take the quantum mechanical aspects into account. These models are reexamined by investigation of the topological 1-manifolds generated by the gradient field of potential functions featuring the electron cloud configuration, such as the electron density or electron localization function (ELF). In this chapter, we reexamine these models in order to escape from the quantum mechanical dilemma and we show how topological analyzes enable to recover these models.
A series of pseudopotential periodic Hartree-Fock calculations has been performed on a V[sub 2]O[... more A series of pseudopotential periodic Hartree-Fock calculations has been performed on a V[sub 2]O[sub 5] crystal. The optimized V-O bond lengths and stretching force constants are found to be in good agreement with experiment. The band structure and density of states are reported, and in contrast with tight-binding calculations there is no gap in the valence band. From the projected density of state it is shown that the V atom d orbitals play an important role in the bonding and therefore that this oxide is partially ionic. Three types of V-O bonds are recognized in this structure: The mainly covalent vanadyl bond, the ionic bond connecting the central vanadium to the chain oxygen, and the electrostatic-van der Waals bond which ensures the stacking of the layers. 29 refs., 9 figs., 3 tabs.
The bonding in KgInll and RbgInl1 has been investigated at the SCF level with the periodic Hartre... more The bonding in KgInll and RbgInl1 has been investigated at the SCF level with the periodic Hartree-Fock method. Comparison is made with In11 clusters with formal charges 7and 8calculated at the same level. The structure of the 7cluster has been optimized; it significantly differs from the structure observed in the condensed phase. The second anion (8-) is found to be dissociative. Moreover, the indium Mulliken populations in clusters are dramatically different from those calculated for the solid phase. This indicates that the reliability of the cluster approach is highly questionable. The stability of the solid phases is mostly due to the electrostatic interactions between the anionic clusters and the alkali counterions. The integrated charge density in the cation region is consistent with a picture in which an electron is delocalized over the potassium layers. The band structure and density of states of the solid phases are discussed. Both &Inll and Rb81nl1 are found to be weak electronic conductors. At the present state of the art, it is not possible to assess the charge borne by the indium cluster and, therefore, to decide whether one or more electrons are delocalized over potassium layers. The bonding in these systems has been investigated from the topological analysis of the electron localization function point of view. The bonding in the In11 anionic clusters is characterized by a network of attractors lying 1 A outward from the indium centers.
An electron localization function and catastrophe theory analysis on the molecular mechanism of g... more An electron localization function and catastrophe theory analysis on the molecular mechanism of gas-phase
The electron localization function (ELF) approach to chemical bonding is revisited as a tool to c... more The electron localization function (ELF) approach to chemical bonding is revisited as a tool to check the falsifiability of the Lewis hypotheses. It is shown that the boundaries of the ELF basins correspond to zero-flux surfaces of the local integrated same spin pair probability enabling the determination of regions of the molecular space which maximizes the opposite spin pair density and therefore groups of electrons. The ELF yields a partition into core and valence basins which matches the Lewis model. The valence basins which correspond either to electron lone pairs or to bonds enable the definition of atomic valence shells in which bonding basins are shared by at least two atomic valence shells. The ELF basin populations take into account the mesomery which explains the deviations from ideal values. The organization of the basins around the atomic cores often complies with the VSEPR rules. The behavior of the ELF basins upon deformation of the nuclear frame sheds light onto the reactivity and reaction mechanisms, whereas the basin compressibilities provide chemical explanations of pressure-induced phase transitions.
The journal of physical chemistry. B, Jan 29, 2009
We present a novel quantitative strategy for monitoring chemical bonding transformations in solid... more We present a novel quantitative strategy for monitoring chemical bonding transformations in solids from the topology of their electronic structure. Developed in the context of the electron localization function formalism, it provides an unambiguous characterization of long-range interactions and bond formation. Charge flux between electron localization regions is found to hold the key for identifying the nature of the interaction between the chemically meaningful entities in the solid (valence shells, lone pairs, molecules, etc.). Because of the wide range of interesting properties that high pressure induces in molecular solids, we illustrate the potentialities of our strategy to unveil controversial questions involved in the bond reorganization along the polymerization of CO2. Our study confirms that the topology of the bonding network in the pseudopolymeric phases points toward the incipient formation of the new bonds in the higher pressure polymers. This transformation is identif...
Accurate electron densities and related functions are sources of chemical information enabling th... more Accurate electron densities and related functions are sources of chemical information enabling the understanding of the structure and chemical properties of molecules and solids. The quantum mechanical backgrounds of the electron probability distribution functions (the electron density and the pair functions), of the electron localization function (ELF), of the source function, and of some other related local descriptors of the electron distribution and of its properties are presented in the first part of this chapter. The rough data provided by these functions do not always reveal all of the expected chemical information, such as the characterization of bonding properties, and, therefore, methodological bridges are necessary to recover the phenomenological chemical concepts. The chapter is focused on the topological approaches that provide a description in the position space consistent with the Lewis structures and with the valence shell electron pair repulsion model. The theory of dynamical systems, applied to the gradient field of the electron density and of the ELF, is the most used mathematical tool enabling a rigorous partition of the space into basins of attractors that are chemically significant and also to propose criteria for a qualitative characterization of the bonding interactions and of their evolution during a chemical reaction. A deep quantitative insight is further achieved by integrating the one particle and pair densities as well as other density of property functions over the basin volumes. The statistical analysis of the variance and covariance of the basin populations provide a measure of the electron delocalization. The use of these techniques of analysis of the electron density properties is illustrated by a series of examples belonging to the field of inorganic chemistry.
Physics of the Earth and Planetary Interiors, 1992
The periodic Hartree-Fock method has been used to sample the potential energy hypersurface of CaO... more The periodic Hartree-Fock method has been used to sample the potential energy hypersurface of CaO to determine a collective reaction pathway between the low-pressure (NaCI) and high-pressure (CsCl) phases. The predicted transition pressure, 68 GPa, is in good agreement with both experimental data and previous theoretical studies. At low pressure the enthalpy (E + P1") surface presents only one minimum corresponding to the Bi (NaCl) structure. A second minimum appears at the B2 (CsCI) geometry when the pressure is increased. The transformation kinetics is estimated using the Johnson-Mehl model coupled to random nucleation and interface-controlled growth. Independently of the interfacial energy, the kinetics is highly pressure dependent. A pressure hysteresis loop is predicted. The results presented are in qualitative agreement with available data.
DFT calculations using the B3LYP functional are reported for a model of the (oxy)tyrosinase activ... more DFT calculations using the B3LYP functional are reported for a model of the (oxy)tyrosinase active site including the two copper cations, six imidazoles and dioxygen (in the oxy form), plus either phenol (taken as a model of tyrosine, the enzyme's natural substrate) or 2-aminophenol, a very efficient inhibitor. The results obtained suggest that (i) both the substrate and the inhibitor have to be deprotonated to form a stable complex with the model of the '' native '' form of the enzyme; (ii) only phenol binds to the oxy form; (iii) the complex formed between our oxy model and 2-aminophenate is more stable than that with phenate, suggesting a competitive inhibition mechanism between the deprotonated forms of the substrate and of the inhibitor.
... Isabelle Fourré,; Bernard Silvi,; Patrick Chaquin,; Alain Sevin. Article first published onli... more ... Isabelle Fourré,; Bernard Silvi,; Patrick Chaquin,; Alain Sevin. Article first published online: 21 MAY 1999. ... Keywords: carbonyl and imine compounds; excitation; electron attachment; ionization; electron localization function; bonding analysis. Abstract. ...
What is a local viewpoint of delocalized bonds? We try to provide an answer to this paradoxical q... more What is a local viewpoint of delocalized bonds? We try to provide an answer to this paradoxical question by investigating representative conjugated organic molecules (namely, allyl cation, trans-butadiene, and benzene) together with reference nonconjugated systems (ethylene and propene) by means of topological analysis of the electron localization function ELF. The valence attractors of the ELF gradient field are classified according to their synaptic order (i.e., connections with core attractors). The basin populations [Formula: see text] (i.e., the integrated density over the attractor basins) and their standard deviation, σ, have been calculated and are discussed. The basin populations and their relative fluctuations, defined as [Formula: see text] are sensitive criteria of delocalization. In the case of well-localized C—C or C=C bonds, λ ~0.4, whereas for delocalized bonds λ increases to about 0.5. Another criterion of delocalization is provided by the basin hierarchy, which is ...
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