Electron localization function from density components

Exploring the Reactivity of Donor-Acceptor Systems through a Combined Conceptual and Constrained DFT Approach

In the context of the conceptual density functional theory (cDFT) and based on the computational efficiency of the constrained DFT (CDFT), we demonstrate that chemical reactivity can be governed by the difference between the local interacting chemical potentials of the reactants (referred as Edual), in agreement with Sanderson's equalization principle. In a proof-of-concept study, we investigated illustrative examples involving typical non-covalent donor-acceptor systems and reactive systems are provided. For the selected systems, our approach reveals significant mimicking between Edual and the DFT-computed intermolecular interaction energy profiles. We further evaluate the influence of the Coulomb and exchange-correlation contributions in Edual. These latter results suggest that numerous potential energy surfaces of clusters can be explored using a Sanderson-like model only based on classical interactions between molecular orbitals domains. To conclude, this study achieved a deeper understanding of the principles of cDFT and assessed, in a wider context, its efficiency in predicting the chemical reactivity.

Complexation and enantioselectivity of novel bridge-like uranyl- 2-((1Z,9Z)-9-(2-Hydroxyphenyl)-3,5,6,8-tetrahydrobenzo[h][1,4,7,10] dioxadiazacyclododecin-2-yl)-5-methoxyphenol with chiral organophosphorus pesticide enantiomers of R/S-malathions

Designing new uranyl complexes with enantioselectivity is of great significance for the identification and separation of enantiomers of chiral pesticides. In this paper, a new asymmetric rigid uranyl-2-((1Z,9Z)-9-(2-Hydroxyphenyl)-3,5,6,8-tetrahydrobenzo[h][1,4,7,10] dioxadiaza-cyclododecin-2-yl)-5-methoxyphenol(Uranyl-HTDM) was designed, we used Uranyl-HTDM as a receptor to selectively coordinate with the guests of the chiral organophosphorus pesticide R/S-malathions(R/S-MLTs) to explore the receptor's enatioselectivity recognition of the chiral guests of R/S-MLTs. Density functional theory (DFT) method was used to comprehensively study the complexation mode of the receptor with enantiomers. The results showed that the U of Uranyl-HTDM could coordinate with both the thiophosphoryl sulfur and carbonyl oxygens of R/S-MLTs in different environments, respectively. The thermodynamics calculations further indicated that the receptor could selectively recognize the thiophosphoryl sulfur and carbonyl oxygen atoms of R/S-malathions, and the complexation abilities of Uranyl-HTDM to the R/S-malathions under different solvents were not the same. The smaller the polarity of solvents, the stronger the complexation ability of Uranyl-HTDM with R-malathion, toluene was an ideal solvent with large △G change and enatioselectivity coefficient of 99.55%. The study provides useful references for the design of new uranyl-salophens and for the experimental study on the molecular recognition of chiral organophosphorus pesticides.

New insights of QTAIM and stress tensor to finding non-competitive/competitive torquoselectivity of cyclobutene

This study aims to investigate the phenomenon of torquoselectivity through three thermal cyclobutene ring-opening reactions (N1-N3). This research focuses on the nature of the chemical bond, electronic reorganization, predicting non-competitive or competitive reactions, and torquoselectivity preference within Quantum Theory of Atoms in Molecules (QTAIM) and stress tensor frameworks. Various theoretical analyses for these reactions, such as metallicity ξ(r_b), ellipticity ε, total local energy density H(r_b), stress tensor polarizability ℙ_σ, stress tensor eigenvalue λ_3σ, and bond-path length, display differently for non-competitive and competitive reactions as well as for the conrotatory preferences either it is the transition state outward conrotatory (TS_out) or transition state inward conrotatory (TS_in) directions by presenting degeneracy or non-degeneracy in their results. The ellipticity profile provides the motion of the bond critical point locations due to the different substituents of cyclobutene. In agreement with experimental results, examinations demonstrated that N1 is a competitive reaction and N2-N3 are non-competitive reactions with TS_out and TS_in preference directions, respectively. The concordant results of QTAIM and stress tensor scalar and vectors with experimental results provide a better understanding of reaction mechanisms.

Exploring The Sequence of Electron Density Along The Chemical Reactions Between Carbonyl Oxides And Ammonia/Water Using Bond Evolution Theory

The molecular mechanism of the reactions between four carbonyl oxides and ammonia/water are investigated using the M06-2X functional together with 6-311++G(d,p) basis set. The analysis of activation and reaction enthalpy shows that the exothermicity of each process increased with the substitution of electron donating substituents (methyl and ethenyl). Along each reaction pathway, two new chemical bonds C-N/C-O and O-H are expected to form. A detailed analysis of the flow of the electron density during their formation have been characterized from the perspective of bonding evolution theory (BET). For all reaction pathways, BET revealed that the process of C-N and O-H bond formation takes place within four structural stability domains (SSD), which can be summarized as follows: the depopulation of V(N) basin with the formation of first C-N bond (appearance of V(C,N) basin), cleavage of N-H bond with the creation of V(N) and V(H) monosynaptic basin, and finally the V(H,O) disynaptic basin related to O-H bond. On the other hand, in the case of water, the cleavage of O-H bond with the formation of V(O) and V(H) basins is the first stage, followed by the formation of the O-H bond as a second stage, and finally the creation of C-O bond.

The Topological Analysis of the ELFx Localization Function: Quantitative Prediction of Hydrogen Bonds in the Guanine-Cytosine Pair

In this contribution, we recall and test a new methodology designed to identify the favorable reaction pathway between two reactants. Applied to the formation of the DNA guanine (G) –cytosine (C) pair, we successfully predict the best orientation between the base pairs held together by hydrogen bonds and leading to the formation of the typical Watson Crick structure of the GC pair. Beyond the global minimum, some local stationary points of the targeted pair are also clearly identified.

New insights in chemical reactivity from quantum chemical topology

Based on the quantum chemical topology of the modified electron localization function ELF_x , an efficient and robust mechanistic methodology designed to identify the favorable reaction pathway between two reactants is proposed. We first recall and reshape how the supermolecular interaction energy can be evaluated from only three distinct terms, namely the intermolecular coulomb energy, the intermolecular exchange-correlation energy and the intramolecular energies of reactants. Thereafter, we show that the reactivity between the reactants is driven by the first-order variation in the coulomb intermolecular energy defined in terms of the response to changes in the number of electrons. Illustrative examples with the formation of the dative bond B-N involved in the BH₃ NH₃ molecule and the typical formation of the hydrogen bond in the canonical water dimer are presented. For these selected systems, our approach unveils a noticeable mimicking of E_dual onto the DFT intermolecular interaction energy surface calculated between the both reactants. An automated reaction-path algorithm aimed to determine the most favorable relative orientations when the two molecules approach each other is also outlined.

Aromatic nature of neutral and dianionic 1,4-diaza-2,3,5,6-tetraborinine derivatives

The aromatically relevant parameters of boron-rich inorganic benzenes-neutral and dianionic 1,4-diaza-2,3,5,6-tetraborinine derivatives (B4N2R6)-have been computationally estimated and evaluated from geometric, electronic, magnetic, and energetic points of view. The majority of the criteria (ASE, NICSzz, ELF, and PDI) indicate that the aromaticity of the neutral B4N2 benzene analogue stabilized by Lewis bases lies in between those of benzene and borazine. On the other hand, the aromaticity of the dianionic B4N2 benzene analogue 4' is controversial. The pronounced aromatic nature of 4' is supported by ELFπ, PDI, and NICSπzz, but ASE, the FiPC-NICS plot, and ACID oppose this. These data confirm that even with the same B4N2-skeletal framework of a 6π-system, the aromatic feature varies depending on the overall charge of the B4N2 systems.