Topological analysis of information-theoretic quantities in density functional theory.

Electrophilicity and nucleophilicity are two vastly important chemical concepts gauging the capability of atoms in molecules to accept and donate the maximal number of electrons. In our earlier studies, we proposed to simultaneously quantify them using the Kullback-Leibler divergence from the information-theoretic approach in density functional theory. However, several issues with this scheme remain to be clarified such as its general validity, predictability, and relationship with other information-theoretic quantities. In this work, we revisit the matter with bigger datasets and deeper theoretical insights. Five information-theoretic quantities including Kullback-Leibler divergence, Hirshfeld charge, Ghost-Berkowitz-Parr entropy, and second and third orders of relative Onicescu information energy are found to be reliable and robust descriptors of electrophilicity and nucleophilicity propensities. Employing these five descriptors, we design a list of new compounds and predict their electrophilicity and nucleophilicity scales. This work should markedly improve our confidence and capability in applying information-theoretic quantities to evaluate electrophilicity and nucleophilicity propensities and henceforth pave the route for more applications of these quantities from information-theoretic approach in density functional theory in the future. All structures were fully optimized at the M06-2X/6-311 + G(d) level of DFT functional using the Gaussian 16 package (version C01) with integration grids and tight self-consistent-field convergence. The solvent effect was taken into account by using the implicit solvent model (CPCM) in the CH2Cl2 solvent, and all 3D contour surfaces of Fukui function, local temperature, and ITA (information-theoretic approach) quantities were generated by GaussView. The Multiwfn 3.8 program was used to calculate the ITA indexes and atomic charges.

Experimental and computational studies of organic 4-[[(4-chlorophenyl)imino]methyl]phenol single crystals for optic and biological applications

In the current study, the molecular structures of the two new azomethine dyes such as AAFOH-1 and AAFOH-2 have been investigated with the use of density functional theory (DFT/B3LYP/6-311+G(d)) in a DMSO solvent for the first time. The electronic spectra of the new dyes in a DMSO solvent were carried out by temporally dependent density functional theory (TD-DFT) method. The computed absorption spectral data of the investigated molecules are in good agreement with the experimental data, thus allowing an assignment of the UV/Vis spectra. The equilibrium geometry, the HOMO and LUMO molecular orbitals, excitation energies, oscillator strengths and natural bond orbital (NBO) analysis for the molecules have also been calculated and presented. The electron location function (ELF), localized orbital locator (LOL), and quantum theory of atoms in molecules (QTAIM) analyses were also carried out. On the basis of polyvinyl alcohol (PVA) and the new synthesized azomethine dyes polarizing films were developed. The main optical parameters of polarizing PVA-films (transmittance, polarization efficiency, and dichroic ratio) have been measured and discussed. Anizotropy of thermal conductivity of the PVA-films have been studied.

The molecular interaction between the chelating agents of citric acid (CA), ethylenediaminetetraacetic acid (EDTA), and triethylenetetraamine (TETA) with metals (M = Ba, Y, and Zr) were studied using Density Functional Theory (DFT) method. This study aims to determine the type of bonding between M–O/N bonds in the CA/EDTA/TETA– complexes. In this study, each metal was attached at strategic positions of chelating agents and was optimized at B3LYP/6-31G* and UGBS level of theory. The M–O bonds were characterized based on Atoms–in–molecules (AIM) and Electron Localization Function (ELF) in the topological analysis. In AIM analysis, the total electron energy density at the bond critical point (BCP) of the M–O/N bonds are used to estimate the interaction involved. The low values of ρ(r) and positive values of ∇2ρ(r) indicates that ionic character exists in the M–O/N bonds. In ELF color-filled map, the blue shaded region between M–O/N atom acts as an indicator for the existence of the ionic interaction. Both AIM and ELF results confirm the existence of ionic bonding between M–O/N bonds, with values of ρ(r) and ∇2ρ(r) ranging from 0.02 to 0.12 au and 0.09 to 0.5 au respectively. Further analysis on charge distribution at M–O/N bonds show that the opposite charge between Ba, Y, and Zr with O/N assured the M– O/N ionic bonding interactions. Keywords: Density functional theory, metals, bonding, atom–in–molecules, bond critical point, electron localization functions

The 5-isopropyl-2-methylphenol (5IP2MP) molecule, a monoterpenoid phenol mostly existing in the essential oil of Origanum vulgare L., was used as a potent breast cancer inhibitor in this present investigation. First, the structural and spectroscopic properties of the 5-isopropyl-2-methylphenol (5IP2MP) molecule were assessed via density functional theory (DFT) calculation. The structural optimization was performed through the DFT/B3LYP method with the 6-311++G (d,p) basis set, and the structural geometry was calculated. From the optimized structure of 5-isopropyl-2-methylphenol, vibrational frequencies were allotted and related with analytically calculated vibrational frequencies, the UV–Visible spectrum was theoretically simulated, and absorbance was experimentally confirmed. The 5-isopropyl-2-methylphenol’s reactive potential was further investigated through a molecular electrostatic potential surface. Exploiting the HOMO-LUMO energies and energy gap, the molecular reactivity and stability of the 5-isopropyl-2-methylphenol molecule were assessed. Mulliken and natural population analysis revealed the charge distribution over the atoms of 5-isopropyl-2-methylphenol. The bioactivity of the 5IP2MP was confirmed through natural bond orbital analysis. Thermodynamic evaluation has been utilized to acquire values of 5-isopropyl-2-methylphenol’s thermodynamic parameters that reveals the thermal stability of the title molecule. To determine the bonding domains and weakest interactions in 5IP2MP, topological investigations have been carried out based on electron localization function, localized orbital locator and reduced density gradient. Through the DPPH assay, the antioxidant potential was confirmed. The physicochemical and pharmacokinetic studies confirm the drug-likeness properties of 5-isopropyl-2-methylphenol. The anti-cancer potential of 5-isopropyl-2-methylphenol in contradiction to breast cancer proteins was confirmed through molecular docking analysis, which showed the highest binding affinity was detected against NAMPT with –7.9 kcal/mol. The previously chosen title chemical might be promoted as a possible pharmacological candidate for the development of new breast cancer prevention medications. The in vitro cytotoxicity studies exhibited the IC50 value of 67.96 [Formula: see text]g/ml with T-47D cells for a time period of 24 h. Overall, this study showed that the 5IP2MP molecule possesses better structural stability, reactivity and excellent anticancer activity in both in silico and in vitro studies.

Breast cancer remains a major worldwide health concern, with current targeted therapies often showing limited effectiveness. Treatment options vary from invasive procedures like surgery to less intrusive methods such as radiotherapy and chemotherapy. To address these constraints, researchers are engaged in the creation of innovative anti-cancer drugs. One promising compound is (E)-4-(1-(2-(4-(4-chlorophenyl)thiazol-2-yl)hydrazono)ethyl)phenol (CTP), which has demonstrated efficacy as an anti-breast cancer agent. The synthesized compound CTP underwent optimization utilizing the Density Functional Theory (DFT) computation applying 6-311 + G(d,p) basis set. The optimized geometry closely matched experimental data, affirming the accuracy of the computational model. Natural Bond Orbital (NBO) analysis provided through comprehension of both intra- and intermolecular interactions. The vibrational properties of CTP were extensively analyzed using FT-IR and Raman spectroscopy. Through the use of Hirshfeld surface analysis, intermolecular interactions within crystal structures were revealed. The electronic structure and non-covalent interactions within CTP were further examined using Localized Orbital Locator (LOL) analyses and Electron Localization Function (ELF). ADMET profiling evaluated the drug-like properties of CTP, while molecular docking with protein 4ZVM predicted key ligand-protein binding sites. The compound CTP was further evaluated in vitro for its potential anticancer properties, specifically targeting the MCF7 breast cancer cell line. The observed red shift in C-S stretching and the broad, weak C-H band provided compelling evidence for both intra- and intermolecular interactions. Negative binding energies from docking studies indicated potential inhibition of human breast cancer by CTP. This comprehensive analysis systematically elucidated the molecular characteristics and interactions of CTP, highlighting its potential as a therapeutic agent for breast cancer.

Si-E bondings in hexacoordinate silicon phthalocyanine were analyzed using bond order (BO), energy partition, atoms in molecules (AIM), electron localization function (ELF), and localized orbital locator (LOL). Bond models were proposed to explain differences between hexacoordinate and tetracoordinate Si-E bondings. Aromaticity of silicon phthalocyanine was investigated using nucleus-independent chemical shift (NICS), harmonic oscillator model of aromaticity (HOMA), conceptual density functional theory (DFT), ring critical point (RCP) descriptors, and delocalization index (DI). Structure, energy, bonding, and aromaticity of tetracoordinate silicon phthalocyanine were studied and compared with hexacoordinate one.

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.

Using simple functionals of the electron density to appreciate and quantify molecular structure and chemical reactivity properties is a recent endeavor in density functional theory (DFT) toward the development of a new chemical reactivity theory. According to the first Hohenberg–Kohn theorem in DFT, the electron density alone should be able to determine any property in the ground state. Exchange and correlation energies are such properties, so are molecular structure and chemical reactivity, and hence they all should accurately be determined by electron density functionals. Quantities such as Shannon entropy, Fisher information, Ghosh–Berkowitz–Parr entropy, information gain, Onicescu information energy, etc., from the information‐theoretic approach are simple electron density functionals, whose analytical forms are exactly known. In this article, we demonstrate their usefulness and validity to quantify regioselectivity, stereoselectivity, and other structure and reactivity properties. We will outline the current understanding of its theoretical framework at first, and then highlight recent applications to chemical problems including isomeric and conformational stability, electrophilicity and nucleophilicity, strong covalent and weak noncovalent interactions, acidity and basicity, aromaticity and antiaromaticity, and numerous other properties. The effort of employing electron density functionals to quantify chemical concepts should open up a new door for us to ultimately develop a chemical reactivity theory using the DFT language.This article is characterized under:Structure and Mechanism > Reaction Mechanisms and CatalysisElectronic Structure Theory > Density Functional TheoryStructure and Mechanism > Molecular StructuresMolecular and Statistical Mechanics > Molecular Interactions

In the last decade the quantum theory of atoms in molecules1 (QTAM) has been increasingly used to highlight many facets of molecular structure, and of chemical reactivity, and to rationalize observed thermochemical or spectroscopical molecular properties. By using only information contained in the molecular charge distribution p(r) and in its associated gradient vector Vp(r) and Laplacian V p(r) fields, the QTAM allows to define the structure of a molecule, its structural stability and the properties of its constituting atoms. It is worth emphasizing that the charge density, which plays a key role in QTAM, is a fundamental quantity in density functional theory, being the ground state wavefunction and energy a unique functional of ρ(r).2 Furthermore ρ(r) is just the three-dimensional single-particle density evinced in diffraction experiments.

Experimental and theoretical investigations were made on the molecule 3,4-dichloro-1,2,5-thiadiazole abbreviated as DCTDA. Density functional theory (DFT) approach with B3LYP functional was employed for the theoretical calculations. Geometrical optimization is performed for the molecule under DFT’s B3LYP functional and MP2 method with basis set 6-311++ G (d, p) on which the entire computational study (Molecular Electrostatic Potential [MEP], Electron localization function [ELF], Natural bond orbital [NBO], Non-Linear optical [NLO], Temperature dependent DFT [TD-DFT] calculations) is made. Spectrochemical studies involved FT-IR and UV-Visible investigations. The molecule’s chemically reactive sites have been explained via MEP andFukui function analysis. NBO analysis was done to explain the acceptor-donor interactions interference energy, and hybridization of the bond generated. Reduced Density Gradient calculations were made to analyze the non-covalent interactions within the molecule. Optical utility along with hyperpolarizability and polarizability are studied with the help of NLO analysis. Vibrational analysis included the Potential Energy Distribution assignments made by the usage of VEDA program. Frontier molecular orbital interactions were studied using the TD-DFT calculations which predicted the probable transitions. Binding of different proteins to the ligand (titled molecule) was effectively done to obtain lowest binding scores (which is found to be −4.5 kcal/mol for DCTDA) indicating to strong receptor (protein)-ligand interactions and thus deduced the very probability of the molecule being biologically active. ELF was used to explain AIM (Atom in Molecule) theory and helps visualize the localization and delocalization of electrons within the molecule. UV-Visible spectroscopy employed using TD-DFT in various solvents to study the charge transfer and the impact of different solvents on the peak position in the spectra. Thermodynamic properties such as entropy, internal energy, enthalpy, Gibb’s free energy, specific heat capacity was calculated for a wide range of temperatures. Certain local descriptors including chemical softness, chemical hardness, chemical potential and electrophilicity index were deduced using the LUMO-HOMO energy gap. Drug likeness was also deduced for DCTDA and various other of its derivatives.

The Huckel’s rule, Baird’s rule, and electronic shell closure model are classical and well-established concepts in chemistry, which have long been employed in rationalizing the aromaticity/antiarom...

Birefringence, polarizability order parameters and DFT calculations in the nematic phase of two bent-core liquid crystals and their correlation

The stepwise formation of actinide formate complexes provides an important framework for understanding actinide-ligand bonding and reactivity. Density functional theory calculations are used to investigate the thermodynamics, kinetics, and electronic structure of formate formation reactions. On the basis of an established uranium-centered mechanism, the effects of halogen substitution (F, Cl, and Br) are examined, followed by a comparative study in which uranium is replaced with thorium, neptunium, and plutonium. The reaction and activation free energies are evaluated for all the elementary steps leading to mono-, bis-, and tris-formate intermediates (IV, VII, and X). The results reveal clear halogen- and actinide-dependent trends in intermediate stability and activation barriers. Complementary noncovalent interaction (NCI), reduced density gradient (RDG), electron localization function (ELF), and localized orbital locator (LOL) analyses reveal that the reaction pathways are governed by localized metal-ligand interactions, providing a unified mechanistic and electronic structure description across the studied actinide series.

(E)-1-benzyl-3-(2-pyridine-2-yl)hydrazono)indolin-2-one (BPHI), an aromatic moiety, were subjected to a collection of theoretical studies with the help of the Gaussian 09, GaussView 6.0, and Multiwfn-3.8 packages of software. Its molecular geometry, bond angle, and bond length are computed theoretically. Vibrational assignments and PED values are calculated theoretically and were corroborated with experimental IR spectra to gain insight and knowledge about the structural details of BPHI. The theoretical determination of the electronic transitions along with photophysical properties for various mediums (viz., gas, acetonitrile, DMSO), including HOMO and LUMO energy gap are theoretically found from time-dependent—density functional theory (TD-DFT). Interpretation of the Fukui function helps in identifying the active sites in BPHI. To study the topology of BPHI, ELF maps (electron localization function) have been utilized. Alongside, detailed analyses of RDG (reduced density gradient) as well as LOL (localized orbital locator) are also carried out. Interactions pertaining to donor and acceptor moiety in BPHI are computed through natural bond analysis. MEP analysis is used to determine the bioactive site of BPHI. 4F5S crystal structure with respect to BSA protein was used for molecular docking with the help of the CB-dock software and docked results are visualized by Molegro molecular view software.