Density Functional Reactivity Theory Research Articles

A conceptual DFT study of the molecular properties of glycating carbonyl compounds

Several glycating carbonyl compounds have been studied by resorting to the latest Minnesota family of density functional with the objective of determinating their molecular properties. In particular, the chemical reactivity descriptors that arise from conceptual density functional theory and chemical reactivity theory have been calculated through a DeltaSCF protocol. The validity of the KID (Koopmans’ in DFT) procedure has been checked by comparing the reactivity descriptors obtained from the values of the HOMO and LUMO with those calculated through vertical energy values. The reactivity sites have been determined by means of the calculation of the Fukui function indices, the condensed dual descriptor Delta {f}(mathbf {r}) and the electrophilic and nucleophilic Parr functions. The glycating power of the studied compounds have been compared with the same property for simple carbohydrates.Graphical abstractSeveral glycating carbonyl compounds have been studied by resorting to the latest Minnesota family of density functional with the objective of determinating their molecular properties, the chemical reactivity descriptors and the validity of the KID (Koopmans’ in DFT) procedure

The charge transfer limit of a chemical adduct: the role of perturbation on external potential

Full profiles of the components (positive and negative) of density functional reactivity theory (DFRT) based stabilization energy with respect to the amount of charge transfer (ΔN) are investigated on three different Diels-Alder pairs and twelve different charge transfer complexes formed by BH3-NH3 and their derivatives. One interesting observation is that the stabilization energy is zero when the charge transfer (ΔN) is either zero (lower limit, L.L.) or two times (higher limit, H.L.) the charge transfer at equilibrium (i.e., when chemical potentials are equalized). However, the existence of zero stabilization energy at the zero charge transfer limit is counter-argued after the inclusion of first and second order effects (due to a perturbing external potential of the partner of a given atom-in-a-molecule) in the individual energy components as well as the overall stabilization energy expressions. It has been shown that even when ΔN is zero (the lower limit), the net energy change is negative (i.e., the combined system is stabilized), highlighting the role of non-bonding interactions, rather than charge-transfer, in stabilizing the combined system at the initial stage of adduct formation. The higher limit (H.L.) of charge transfer is also shifted to a much lower value due to the inclusion of this external potential perturbation.

Evaluating frontier orbital energy and HOMO/LUMO gap with descriptors from density functional reactivity theory.

Wave function theory (WFT) and density functional theory (DFT)-the two most popular solutions to electronic structure problems of atoms and molecules-share the same origin, dealing with the same subject yet using distinct methodologies. For example, molecular orbitals are artifacts in WFT, whereas in DFT, electron density plays the dominant role. One question that needs to be addressed when using these approaches to appreciate properties related to molecular structure and reactivity is if there is any link between the two. In this work, we present a piece of strong evidence addressing that very question. Using five polymeric systems as illustrative examples, we reveal that using quantities from DFT such as Shannon entropy, Fisher information, Ghosh-Berkowitz-Parr entropy, Onicescu information energy, Rényi entropy, etc., one is able to accurately evaluate orbital-related properties in WFT like frontier orbital energies and the HOMO (highest occupied molecular orbital)/LUMO (lowest unoccupied molecular orbital) gap. We verified these results at both the whole molecule level and the atoms-in-molecules level. These results provide compelling evidence suggesting that WFT and DFT are complementary to each other, both trying to comprehend the same properties of the electronic structure and molecular reactivity from different perspectives using their own characteristic vocabulary. Hence, there should be a bridge or bridges between the two approaches.

Information Functional Theory: Electronic Properties as Functionals of Information for Atoms and Molecules.

How to accurately predict electronic properties of a Columbic system with the electron density obtained from experiments such as X-ray crystallography is still an unresolved problem. The information-theoretic approach recently developed in the framework of density functional reactivity theory is one of the efforts to address the issue. In this work, using 27 atoms and 41 molecules as illustrative examples, we present a study to demonstrate that one is able to satisfactorily describe such electronic properties as the total energy and its components with information-theoretic quantities like Shannon entropy, Fisher information, Ghosh-Berkowitz-Parr entropy, and Onicescu information energy. Closely related to the earlier attempt of expanding density functionals using simple homogeneous functionals, this work not only confirms Nagy's proof that Shannon entropy alone should contain all the information needed to adequately describe an electronic system but also provides a feasible pathway to map the relationship between the experimentally available electron density and various electronic properties for Columbic systems such as atoms and molecules. Extensions to other electronic properties are straightforward.

A density functional reactivity theory (DFRT) based approach to understand the effect of symmetry of fullerenes on the kinetic, thermodynamic and structural aspects of carbon NanoBuds

In the present study, we have rationalized the effect of variation in the symmetry of relatively smaller fullerene (C32) on the mode of its interaction with semi-conducting Single-Walled Carbon Nanotubes (SWCNTs) in the process of formation of stable hybrid carbon NanoBuds. Thermodynamic and kinetic parameters, along with the charge transfer values associated with the interaction between fullerene and SWCNTs, have been evaluated using an un-conventional and computationally cost–effective method based on density functional reactivity theory (DFRT). In addition to this, conventional DFT based studies are also performed to substantiate the growth of NanoBud structures formed by the interaction between fullerene and SWCNTs. The findings of the present study suggest that the kinetic, thermodynamic and structural aspects of hybrid carbon NanoBuds are significantly influenced by both the symmetry of C32 fullerene and its site of covalent attachment to the SWCNT.

ChemInform Abstract: A Combined Experimental and Theoretical Study of the Ammonium Bifluoride Catalyzed Regioselective Synthesis of Quinoxalines and Pyrido[2,3-b]pyrazines.

Ammonium bifluoride was efficiently used at a 0.5 mol% loading to catalyze the cyclocondensation of 1,2-arylenediamines with 1,2-dicarbonyl compounds at room temperature in methanol–water to give quinoxalines or pyrido[2,3-b]pyrazines in excellent yields. Importantly, 2,8-disubstituted quinoxalines and 3-substituted pyrido[2,3-b]pyrazines were regioselectively formed by the reaction of arylglyoxals with 3-methylbenzene-1,2-diamine or pyridine-2,3-diamine, respectively. An analysis of the density functional theory reactivity indices explained the catalytic role of ammonium bifluoride.

Theoretical evaluation of triazine derivatives as steel corrosion inhibitors: DFT and Monte Carlo simulation approaches

Density functional theory (DFT) calculations and atomistic Monte Carlo simulations were performed on hexahydro-1,3,5-triphenyl-s-triazine (Inh1), hexahydro-1,3,5-p-tolyl-s-triazine (Inh2), hexahydro-1,3,5-p-methoxyphenyl-s-triazine (Inh3), hexahydro-1,3,5-p-aminophenyl-s-triazine (Inh4), hexahydro-1,3,5-p-nitrophenyl-s-triazine (Inh5) molecules in order to study their reactivity and adsorption behaviour towards steel corrosion. DFT results indicate that the active sites of the molecules were mainly located on the N atoms of the triazine ring and on the aromatic rings containing substituted polar groups. Monte Carlo simulations were applied to search for the most stable configuration for the adsorption of the inhibitor molecules on Fe(110) surface both in vacuum and in aqueous solution. The investigated molecules exhibited strong interactions with iron surface. In aqueous solution all the investigated molecules displaced water molecules and were strongly attracted to the Fe surface as evident in their large negative adsorption energies compared to that in vacuum. The DFT reactivity indicators as well as the adsorption strength from the outputs of Monte Carlo simulations of the studied molecules on Fe(110) surface in vacuum and in the presence of water follow the trend: Inh4 > Inh3 > Inh2 > Inh1 > Inh5. The theoretical data obtained are in good agreement with the experimental inhibition efficiency results earlier reported.

A Long-Lived Fe(III)-(Hydroperoxo) Intermediate in the Active H200C Variant of Homoprotocatechuate 2,3-Dioxygenase: Characterization by Mössbauer, Electron Paramagnetic Resonance, and Density Functional Theory Methods.

The extradiol-cleaving dioxygenase homoprotocatechuate 2,3-dioxygenase (HPCD) binds substrate homoprotocatechuate (HPCA) and O2 sequentially in adjacent ligand sites of the active site Fe(II). Kinetic and spectroscopic studies of HPCD have elucidated catalytic roles of several active site residues, including the crucial acid-base chemistry of His200. In the present study, reaction of the His200Cys (H200C) variant with native substrate HPCA resulted in a decrease in both kcat and the rate constants for the activation steps following O2 binding by >400 fold. The reaction proceeds to form the correct extradiol product. This slow reaction allowed a long-lived (t1/2 = 1.5 min) intermediate, H200C-HPCAInt1 (Int1), to be trapped. Mössbauer and parallel mode electron paramagnetic resonance (EPR) studies show that Int1 contains an S1 = 5/2 Fe(III) center coupled to an SR = 1/2 radical to give a ground state with total spin S = 2 (J > 40 cm(-1)) in Hexch = JŜ1·ŜR. Density functional theory (DFT) property calculations for structural models suggest that Int1 is a (HPCA semiquinone(•))Fe(III)(OOH) complex, in which OOH is protonated at the distal O and the substrate hydroxyls are deprotonated. By combining Mössbauer and EPR data of Int1 with DFT calculations, the orientations of the principal axes of the (57)Fe electric field gradient and the zero-field splitting tensors (D = 1.6 cm(-1), E/D = 0.05) were determined. This information was used to predict hyperfine splittings from bound (17)OOH. DFT reactivity analysis suggests that Int1 can evolve from a ferromagnetically coupled Fe(III)-superoxo precursor by an inner-sphere proton-coupled-electron-transfer process. Our spectroscopic and DFT results suggest that a ferric hydroperoxo species is capable of extradiol catalysis.

Interaction between Small Gold Clusters and Nucleobases: A Density Functional Reactivity Theory Based Study

The thermodynamic and kinetic aspects associated with the interaction of small gold clusters (Aun, where n = 3–6) with nucleobases are assessed using a density functional reactivity theory based comprehensive decomposition analysis of stabilization energy scheme. It is observed that the trend of interaction between Aun clusters and nucleobases follows the order G > A > C > T > U. Also, the Watson–Crick base pair GC interacts with Aun clusters more preferably than that of the AT pair. The observed trend is further supported by conventional binding energy and transition-state calculations at B3PW91 and MP2 levels.

Computational Study of Chemical Reactivity Using Information-Theoretic Quantities from Density Functional Reactivity Theory for Electrophilic Aromatic Substitution Reactions.

The electrophilic aromatic substitution for nitration, halogenation, sulfonation, and acylation is a vastly important category of chemical transformation. Its reactivity and regioselectivity is predominantly determined by nucleophilicity of carbon atoms on the aromatic ring, which in return is immensely influenced by the group that is attached to the aromatic ring a priori. In this work, taking advantage of recent developments in quantifying nucleophilicity (electrophilicity) with descriptors from the information-theoretic approach in density functional reactivity theory, we examine the reactivity properties of this reaction system from three perspectives. These include scaling patterns of information-theoretic quantities such as Shannon entropy, Fisher information, Ghosh-Berkowitz-Parr entropy and information gain at both molecular and atomic levels, quantitative predictions of the barrier height with both Hirshfeld charge and information gain, and energetic decomposition analyses of the barrier height for the reactions. To that end, we focused in this work on the identity reaction of the monosubstituted-benzene molecule reacting with hydrogen fluoride using boron trifluoride as the catalyst in the gas phase. We also considered 19 substituting groups, 9 of which are ortho/para directing and the other 9 meta directing, besides the case of R = -H. Similar scaling patterns for these information-theoretic quantities found for stable species elsewhere were disclosed for these reactions systems. We also unveiled novel scaling patterns for information gain at the atomic level. The barrier height of the reactions can reliably be predicted by using both the Hirshfeld charge and information gain at the regioselective carbon atom. The energy decomposition analysis ensued yields an unambiguous picture about the origin of the barrier height, where we showed that it is the electrostatic interaction that plays the dominant role, while the roles played by exchange-correlation and steric effects are minor but indispensable. Results obtained in this work should shed new light for better understanding of the factors governing the reactivity for this class of reactions and assisting ongoing efforts for the design of new and more efficient catalysts for such kind of transformations.

Effect of external electric field on Cyclodextrin-Alcohol adducts: A DFT study

Effect of external electric fields on the interaction energy between cyclodextrin and alcohol was analyzed in the light of density functional theory (DFT) and density functional reactivity theory (DFRT). Stability of the cyclodextrin-alcohol adducts was measured in terms of DFT based reactivity descriptor, global hardness, electrophilicity, and energy of the HOMO. Stability of adducts was observed to be sensitive towards the strength as well as direction of the applied external electric field. In addition, reactivity pattern follows the maximum hardness and minimum electrophilicity principles. Cyclodextrin-alcohol adducts show remarkable response towards the strength and direction of the applied electric field.

A Combined Experimental and Theoretical Study of the Ammonium Bifluoride Catalyzed Regioselective Synthesis of Quinoxalines and Pyrido[2,3-b]pyrazines

Ammonium bifluoride was efficiently used at a 0.5 mol% loading to catalyze the cyclocondensation of 1,2-arylenediamines with 1,2-dicarbonyl compounds at room temperature in methanol–water to give quinoxalines or pyrido[2,3-<i>b</i>]pyrazines in excellent yields. Importantly, 2,8-disubstituted quinoxalines and 3-substituted pyrido[2,3-<i>b</i>]pyrazines were regioselectively formed by the reaction of arylglyoxals with 3-methylbenzene-1,2-diamine or pyridine-2,3-diamine, respectively. An analysis of the density functional theory reactivity indices explained the catalytic role of ammonium bifluoride.

Origin of molecular conformational stability: perspectives from molecular orbital interactions and density functional reactivity theory.

To have a quantitative understanding about the origin of conformation stability for molecular systems is still an unaccomplished task. Frontier orbital interactions from molecular orbital theory and energy partition schemes from density functional reactivity theory are the two approaches available in the literature that can be used for this purpose. In this work, we compare the performance of these approaches for a total of 48 simple molecules. We also conduct studies to flexibly bend bond angles for water, carbon dioxide, borane, and ammonia molecules to obtain energy profiles for these systems over a wide range of conformations. We find that results from molecular orbital interactions using frontier occupied orbitals such as the highest occupied molecular orbital and its neighbors are only qualitatively, at most semi-qualitatively, trustworthy. To obtain quantitative insights into relative stability of different conformations, the energy partition approach from density functional reactivity theory is much more reliable. We also find that the electrostatic interaction is the dominant descriptor for conformational stability, and steric and quantum effects are smaller in contribution but their contributions are indispensable. Stable molecular conformations prefer to have a strong electrostatic interaction, small molecular size, and large exchange-correlation effect. This work should shed new light towards establishing a general theoretical framework for molecular stability.

Effect of external electric field on ground and singlet excited states of phenylalanine: A theoretical study

The effect of external electric field on the ground and few singlet excited states of phenyalanine are studied in the light of TDDFT (time dependent density functional theory) and DFRT (density functional reactivity theory). The excited state geometries are compared with the ground state ones. Sensitivity of the reactivity parameters such as total electronic energy, energy of the HOMO (highest occupied molecular orbital), global hardness (η), electrophilicity (ω) etc. towards the external electric fields are measured by varying the applied field strength. Variation of aromaticity of the ground and excited states are gauged in terms of nucleus independent chemical shift (NICS). Geometry, reactivity and aromaticity of the ground as well as excited states are responsive to the presence of external electric field.

Comment on "Scaling properties of information-theoretic quantities in density functional reactivity theory" by C. Rong, T. Lu, P. W. Ayers, P. K. Chattaraj and S. Liu, Phys. Chem. Chem. Phys., 2015, 17, 4977-4988.

The scaling properties of density functionals are key for fundamentally understanding density functional theory. Accordingly, the dependence of density functionals on the number of particles is of paramount relevance. The numerical exploration by Rong et al. addressed N-scaling for a set of quantum information quantities; they found linear relationships between each one of them and the electronic population for atoms, molecules, and atoms in molecules. The main motivation for their computational work was that the theoretical scaling of these quantities is unknown; however, these scaling properties can be analytically determined. Here I reveal the derivation of the N-scaling rules for the quantities studied by Rong et al. by following the procedure introduced in Comput. Theor. Chem., 2015, 1053, 38. In addition, a new atomic scaling rule explains the linear relationship between atomic populations and atomic values of the same quantum information quantities.

Scaling properties of information-theoretic quantities in density functional reactivity theory.

Density functional reactivity theory (DFRT) employs the electron density and its related quantities to describe reactivity properties of a molecular system. Quantities from information theory such as Shannon entropy, Fisher information, and Ghosh-Berkowitz-Parr entropy are natural descriptors within the DFRT framework. They have been previously employed to quantify electrophilicity, nucleophilicity and the steric effect. In this work, we examine their scaling properties with respect to the total number of electrons. To that end, we considered their representations in terms of both the electron density and the shape function for isolated atoms and neutral molecules. We also investigated their atomic behaviors in different molecules with three distinct partitioning schemes: Bader's zero-flux, Becke's fuzzy atom, and Hirshfeld's stockholder partitioning. Strong linear relationships of these quantities as a function of the total electron population are reported for atoms, molecules, and atoms in molecules. These relationships reveal how these information-theoretic quantities depend on the molecular environment and the electron population. These trends also indicate how these quantities can be used to explore chemical reactivity for real chemical processes.

Rényi Entropy, Tsallis Entropy and Onicescu Information Energy in Density Functional Reactivity Theory

Density functional theory dictates that the electron density determines everything in a molecular system's ground state, including its structure and reactivity properties. However, little is known about how to use density functionals to predict molecular reactivity. Density functional reactivity theory is an effort to fill this gap: it is a theoretical and conceptual framework through which electron-related functionals can be used to accurately predict structure and reactivity. Such density functionals include quantities from the information-theoretic approach, such as Shannon entropy and Fisher information, which have shown great potential as reactivity descriptors. In this work, we introduce three closely related quantities: Renyi entropy, Tsallis entropy, and Onicescu information energy. We evaluated these quantities for a number of neutral atoms and molecules, revealing their scaling properties with respect to electronic energy and the total number of electrons. In addition, using the example of second-order Onicescu information energy, we examined how its patterns change with the angle of dihedral rotation of an ethane molecule at both the molecular level and atoms-in-molecules level. Using these quantities as additional reactivity descriptors, researchers can more accurately predict the structure and reactivity of molecular systems.

Density functional reactivity theory study of SN2 reactions from the information-theoretic perspective.

As a continuation of our recent efforts to quantify chemical reactivity with quantities from the information-theoretic approach within the framework of density functional reactivity theory, the effectiveness of applying these quantities to quantify electrophilicity for the bimolecular nucleophilic substitution (SN2) reactions in both gas phase and aqueous solvent is presented in this work. We examined a total of 21 self-exchange SN2 reactions for the compound with the general chemical formula of R1R2R3C-F, where R1, R2, and R3 represent substituting alkyl groups such as -H, -CH3, -C2H5, -C3H7, and -C4H9 in both gas and solvent phases. Our findings confirm that scaling properties for information-theoretic quantities found elsewhere are still valid. It has also been verified that the barrier height has the strongest correlation with the electrostatic interaction, but the contributions from the exchange-correlation and steric effects, though less significant, are indispensable. We additionally unveiled that the barrier height of these SN2 reactions can reliably be predicted not only by the Hirshfeld charge and information gain at the regioselective carbon atom, as previously reported by us for other systems, but also by other information-theoretic descriptors such as Shannon entropy, Fisher information, and Ghosh-Berkowitz-Parr entropy on the same atom. These new findings provide further insights for the better understanding of the factors impacting the chemical reactivity of this vastly important category of chemical transformations.

Nature of Sigma-Type Lithium Bonding Interaction in Nanoscale

Li-based rechargeable batteries are becoming popular power sources for biomedical devices and healthcare equipment. In nanoscale, lithium bonds may associate with intermolecular noncovalent interactions when Li atoms are shared by adjacent atoms inside rechargeable Li batteries. Theoretical study of lithium boding interactions thus is of paramount importance for a better understanding of the working mechanisms and designing high-efficient electrode–electrolyte interfaces from nanolevel for Li-based batteries. In this study, we used state-of-the-art theoretical methods, with inclusion of density functional theory/symmetry-adapted perturbation theory (DFT/SAPT), density functional reactivity theory (DFRT) and energy decomposition analysis (EDA), to delve into the nature of lithium bonding interactions. Our results showed that B3LYP outperforms all other functionals under consideration in the conventional supramolecular scheme, indicating that the formation of a lithium bond is not dispersion-driven. The calculated PBE0/SAPT and B3LYP/EDA data are consistent with each other, unravelling that the lithium bond is mainly of an electrostatically driven nature. Both steric hindrance and exchange-correlation potentials also make important contributions when two-variable fitting is considered. These results provide new sight in understanding lithium atom interactions for potential lithium-based batteries applications.

Where does the electron go? The nature of ortho/para and meta group directing in electrophilic aromatic substitution.

Electrophilic aromatic substitution as one of the most fundamental chemical processes is affected by atoms or groups already attached to the aromatic ring. The groups that promote substitution at the ortho/para or meta positions are, respectively, called ortho/para and meta directing groups, which are often characterized by their capability to donate electrons to or withdraw electrons from the ring. Though resonance and inductive effects have been employed in textbooks to explain this phenomenon, no satisfactory quantitative interpretation is available in the literature. Here, based on the theoretical framework we recently established in density functional reactivity theory (DFRT), where electrophilicity and nucleophilicity are simultaneously quantified by the Hirshfeld charge, the nature of ortho/para and meta group directing is systematically investigated for a total of 85 systems. We find that regioselectivity of electrophilic attacks is determined by the Hirshfeld charge distribution on the aromatic ring. Ortho/para directing groups have most negative charges on the ortho/para positions, while meta directing groups often possess the largest negative charge on the meta position. Our results do not support that ortho/para directing groups are electron donors and meta directing groups are electron acceptors. Most neutral species we studied here are electron withdrawal in nature. Anionic systems are always electron donors. There are also electron donors serving as meta directing groups. We predicted ortho/para and meta group directing behaviors for a list of groups whose regioselectivity is previously unknown. In addition, strong linear correlations between the Hirshfeld charge and the highest occupied molecular orbital have been observed, providing the first link between the frontier molecular orbital theory and DFRT.