Density Functional Reactivity Theory Research Articles

Synthesis of Novel Nitro-Halogenated Aryl-Himachalene Sesquiterpenes from Atlas Cedar Oil Components: Characterization, DFT Studies, and Molecular Docking Analysis against Various Isolated Smooth Muscles.

We report the synthesis of two novel halogenated nitro-arylhimachalene derivatives: 2-bromo-3,5,5,9-tetramethyl-1-nitro-6,7,8,9-tetrahydro-5H-benzo[7]annulene (bromo-nitro-arylhimachalene) and 2-chloro-3,5,5,9-tetramethyl-1,4-dinitro-6,7,8,9-tetrahydro-5H-benzo[7]annulene (chloro-dinitro-arylhimachalene). These compounds were derived from arylhimachalene, an important sesquiterpene component of Atlas cedar essential oil, via a two-step halogenation and nitration process. Characterization was performed using 1H and 13C NMR spectrometry, complemented by X-ray structural analysis. Quantum chemical calculations employing density functional theory (DFT) with the Becke3-Lee-Yang-parr (B3LYP) functional and a 6-31++G(d,p) basis set were conducted. The optimized geometries of the synthesized compounds were consistent with X-ray structure data. Frontier molecular orbitals and molecular electrostatic potential (MEP) profiles were identified and discussed. DFT reactivity indices provided insights into the compounds' behaviors. Moreover, Hirshfeld surface and 2D fingerprint analyses revealed significant intermolecular interactions within the crystal structures, predominantly H-H and H-O contacts. Molecular docking studies demonstrate strong binding affinities of the synthesized compounds to the active site of protein 7B2W, suggesting potential therapeutic applications against various isolated smooth muscles and neurotransmitters.

Perturbed reactivity descriptors in the grand canonical ensemble

Departing from the framework provided by the grand canonical ensemble, the conceptual density functional theory reactivity indexes for isolated systems are modified to incorporate through a first order perturbation approach the effects on them induced by the presence of another interacting species. The general procedure established leads to the same perturbed expressions for the chemical potential and the hardness previously developed and allows one to derive the perturbed expressions for the Fukui function and the dual descriptor. The expressions obtained include the effects on the reactivity indexes of a given species when it interacts with another one, through additional parameters that can be determined to satisfy known specific conditions associated with the interacting systems studied, to improve the description of their chemical reactivity.

Novel triphenylamine-based porphyrins: Synthesis, structural characterization, and theoretical investigation for dye-sensitized solar cell applications

In this work, we have synthesized a series of novel porphyrin derivatives, 8, 12, and 16 in high yields. The new porphyrin derivatives are equipped with different aromatic substituents at the peripheral position. The structures of the new compounds were confirmed by elemental and spectral analyses. Among these porphyrin structures, porphyrins 8, 12, and 16 were molecularly designed and synthesized based on triphenylamine (TPA), as the core donor (DTPA), linked to one, two, or three porphyrin (DPorph) moieties with different numbers of anchoring groups (AG) to generate: DTPA-π-DPorph-A(DE1), DTPA(π-DPorph-A)2(DE2) and DTPA(π-DPorph-A)3(DE3). The structural, electronic, and spectroscopic properties of the dyes have been obtained by using the density functional theory (DFT) and time-dependent-DFT calculations. Based on the DFT studies, porphyrins 8, 12, and 16 possess all thermodynamics requirements to be used for DSSCs as the HOMO values for these three porphyrins are greater than the electrolyte's redox potential (I−/I3−, -5.2 eV), while the LUMO level more negative than the conduction band of TiO2 (- 4.2 eV), which indicate that these structures are suitable as sensitizers in DSSCs. All proposed structures were estimated in the gaseous state based on their optimized ground state geometry to estimate their EHOMO, ELUMO, and HOMO-LUMO energy gaps. porphyrins 8, 12, and 16 electronic excitations were also probed using TD-DFT experiments, which were performed under the impact of time-dependent disturbances. The simulated absorption spectra of these structures revealed the porphyrins' typical Soret- and Q-bands. porphyrin 16 with tri-cyanoacrylic acid anchoring groups has a wider absorption spectrum than other porphyrins (8, 12), and their Soret- and Q-bands are red-shifted. As a final step, we analyzed and described the DSSC's performance using the concept of DFT reactivity indices. A more efficient DSSC can be built using this approach to correlate cell efficiency with molecular properties.

Electronic properties and chemical reactivity of biogenic amine neurotransmitters in gas and solution phase: A DFT study

To understand the bio-physiological effect and neurotoxicity of the oxidized species of the biogenic amine neurotransmitters(e.g. dopamine, epinephrine, norepinephrine, histamine and serotonin), we studied theoretically the electronic properties and chemical reactivity of the neurotransmitters in gas and solution phase at the molecular level using density functional theory (DFT) and density functional reactivity theory (DFRT). The antioxidant capacity, relative stability of cationic and anionic species of the neurotransmitters, neurotransmitter-drug (or receptor) interactions, prediction of agonist and antagonist character of the neurotransmitters have been discussed with the help of vertical ionization potential (VIP), electron affinity (EA), non-adiabatic reduction potential (NRP), vertical detachment energy (VDE), spin density distributions (SDD), various chemical reactivity descriptors, electrostatic potential (ESP) surfaces and mapped electron density analysis. The information obtained from these studies will be useful in clinical neurochemistry, finding the origin of neurological disorders and designing suitable drugs for remedy.

Molecular Interactions From the Density Functional Theory for Chemical Reactivity: The Interaction Energy Between Two-Reagents.

Reactivity descriptors indicate where a reagent is most reactive and how it is most likely to react. However, a reaction will only occur when the reagent encounters a suitable reaction partner. Determining whether a pair of reagents is well-matched requires developing reactivity rules that depend on both reagents. This can be achieved using the expression for the minimum-interaction-energy obtained from the density functional reactivity theory. Different terms in this expression will be dominant in different circumstances; depending on which terms control the reactivity, different reactivity indicators will be preferred.

Spectroscopic Investigations, Computational Studies and Molecular Properties of Naphthalene Derivatives

Theoretical studies have been carried out on bio active molecules such as Naphthalene (npa) and its derivatives naphthalene-2-sulfonic acid (nsa) and 1-nitroso-2-naphthol (nnol) using both Ab initio HF and DFT-B3LYP methods with 6-311++G(d,2p) basis sets. The geometrical parameters, molecular properties and vibrational spectra of nsa, nnol and npa were calculated and analyzed. Geometrical optimizations of the nsa, nnol and npa molecules were done by Density Functional Theory (DFT) using the B3LYP function and Hartree-Fock (HF) level with 6-311++G(d,2p) basis set. The optimized molecular geometry and computed vibrational spectra are compared with experimental results which show significant agreement. DFT and HF global chemical reactivity descriptors (chemical hardness, total energy, electronic chemical otential and electrophilicity) are calculated for the title molecules and used to predict their relative stability and reactivity.

Revisiting the trapping of noble gases (He-Kr) by the triatomic H3+ and Li3+ species: a density functional reactivity theory study.

Small atomic clusters with exotic stability, bonding, aromaticity, and reactivity properties can be made use of for various purposes. In this work, we revisit the trapping of noble gas atoms (He-Kr) by the triatomic H3+ and Li3+ species by using some analytical tools from density functional theory, conceptual density functional theory, and the information-theoretic approach. Our results showcase that though similar in geometry, H3+ and Li3+ exhibit markedly different behavior in bonding, aromaticity, and reactivity properties after the addition of noble gas atoms. Moreover, the exchange-correlation interaction and steric effect are key energy components in stabilizing the clusters. This study also finds that the origin of the molecular stability of these species is due to the spatial delocalization of the electron density distribution. Our work provides an additional arsenal towards a better understanding of small atomic clusters capturing noble gases.

H3PO4 activation mediated the iron phase transformation and enhanced the removal of bisphenol A on iron carbide-loaded activated biochar

Zero valent iron-loaded biochar (Fe0-BC) has shown promise for the removal of various organic pollutants, but is restricted by reduced specific surface area, low utilization efficiency and limited production of reactive oxygen species (ROS). In this study, iron carbide-loaded activated biochar (Fe3C-AB) with a high surface area was synthesized through the pyrolysis of H3PO4 activated biochar with Fe(NO3)3, tested for removing bisphenol A (BPA) and elucidated the adsorption and degradation mechanisms. As a result, H3PO4 activated biochar was beneficial for the transformation of Fe0 to Fe3C. Fe3C-AB exhibited a significantly higher removal rate and removal capacity for BPA than that of Fe0-BC within a wide pH range of 5.0–11.0, and its performance was maintained even under extremely high salinity and different water sources. Moreover, X-ray photoelectron spectra and density functional theory calculations confirmed that hydrogen bonds were formed between the COOH groups and BPA. 1O2 was the major reactive species, constituting 37.0% of the removal efficiency in the degradation of BPA by Fe3C-AB. Density functional reactivity theory showed that degradation pathway 2 of BPA was preferentially attacked by ROS. Thus, Fe3C-AB with low cost and excellent recycling performance could be an alternative candidate for the efficient removal of contaminants.

Role of heteroatoms and substituents on the structure, reactivity, aromaticity, and absorption spectra of pyrene: a density functional theory study

Abstract Effect of heteroatoms viz. BN and substituents viz. –Me (methyl), –OH (hydroxyl), –NH2 (amine), –COOH (carboxyl), and –CN (cyano) on the structural parameters, global reactivity, aromaticity, and UV-visible spectra of pyrene are studied with the help of density functional theory (DFT). Global reactivity parameters such as global hardness (η) and electrophilicity (ω) are calculated using density functional reactivity theory (DFRT). Time dependent density functional theory (TD-DFT) is explored for interpreting the UV-visible absorption spectra. Aromaticity of the pyrene rings are predicted from the nucleus independent chemical shift (NICS) values. Presence of BN unit and substituent induces reasonable impact on the studied parameters. The observed absorption spectra lie predominantly within the UV-region (both blue and red shifts are observed in presence of BN and substituent). HOMO energy and absorption spectra are affected nominally in solvent phase.

A DFT study on the mechanism and selectivity of [3 + 2] cycloaddition reactions leading to pyrole[2,1-a] phthalazine compounds

The mechanism of [3 + 2] cycloaddition (32CA) reactions of phthalazinium-2-dicyanomethanide with electron-deficient and electron-rich ethylenes has been studied using density functional theory (DFT) methods at the M06-2X/cc-pVDZ level of theory. The energy results indicated that the regio- and stereoselectivity of the two 32CA reactions oppose one another, which is in agreement with the experimental report. Accordingly, in the 32CA reaction of phthalazinium-2-dicyanomethanide 1 with methyl vinyl ketone 2a, an electron poor dipolarophile, the meta/endo pathway was more stable than others, while the ortho/exo pathway was the most stable for the 32CA reaction of phthalazinium-2-dicyanomethanide 1 with 1-methoxy-4-vinyl benzene 2b, an electron-rich dipolarophile. Moreover, DFT reactivity indices were studied for the reagents to explain the nucleophilicity and electrophilicity of reagents and selectivity of the reactions. The electron rearrangements along the preferred pathways of these 32CA reactions were studied using the topological analysis of the electron localization function (ELF). The ELF analysis revealed that the reactions proceed through a two-stage one-step mechanism. The noncovalent interactions topological analysis of the possible pathways of the reactions revealed that in addition to strong attractive and repulsive interactions, the weak non-covalent interactions and the steric repulsive interactions have important roles in the determination of the preferred regio- and stereoselective pathway.

Evaluating and understanding the affinity of metal ions to water and ammonia using density functional theory calculation

Affinity, which is the essential attribute of metal ions, is very important to their physical and chemical properties. To make quantitative description and deep understanding on the affinity, fourteen metal ions were considered, and two representative ligands (H2O and NH3) were selected. Five types of energy of five models have been calculated using the density functional theory. Then, the results have been applied to quantify the affinity and describe its evolution in the ligand exchange process. Three aspects, energy decomposition analysis, natural bond orbital analysis, and information-theoretic approach in density functional reactivity theory, have been considered to understand the affinity.

DFT Computational Studies on Some Cobaloximes

This study carried out quantum chemical investigations on cobaloxime complexes: [Co(dpgH)2Cl(H2O)] (C1), [Co(dpgH)2(Pz)Cl] (C2), [Co(dpgH)2(Im)Cl] (C3), [Co(dpgH)2(py)Cl] (C4) and [Co(dpgH)2 (CH3)(py)Cl] (C5), where dpgH− is diphenyl glyoximate, Pz is pyrazine, Im is imidazole and py is pyridine. The stable molecular geometries of these complexes were achieved using density functional theory (DFT) methods. The values of the geometrical parameters obtained from optimized cobaloxime complexes were compatible with experimental data. In order to predict the chemical reactivity of the complexes, their frontier molecular orbital (FMO) energies and their reactivity parameters based on DFT were calculated for optimized cobaloxime complexes. The interaction of the cobaloximes with different DNA bases and Watson–Crick base pairs (A–T and G–C) were explored on the basis of the different reactivity parameters of density functional reactivity theory (DFRT). The results revealed that cobaloximes studied generally acted as an electron-acceptor agent in their interaction with biomolecules. The order of interaction of cobaloximes with all biomolecules followed the sequence C1 > C2 > C3 > C4 > C5.

Computational insight into the mechanism and origin of high regioselectivity in the ring-opening cyclization of spirocyclopropanes with stabilized sulfonium ylides by the DFT.

Chromanes with high bioactivity play an important role in nature, and cyclization reactions of cyclopropanes with sulfonium ylides to form chromane skeletons have attracted great attention of scientists. The mechanism as well as origins of regioselectivity and stereoselectivity for the ring-opening/cyclization reactions between cyclohexane-1,3-dione-2-spirocyclopropanes and stabilized sulfonium ylides in CH2Cl2 were investigated by using the density functional theory (DFT) M06-2X/6-311+G(d,p)//M06-2X/6-31G(d,p) method combined with the SMD model. The calculated results revealed that the reaction process involved two key steps: the ring-opening step and the cyclization step, with the former being the rate-determining and stereoselectivity-determining step. The regioselectivity of the ring-opening step of spirocyclopropane indicated that the tertiary carbon was more preferential than the secondary one when sulfonium ylide attacked spirocyclopropane. The theoretical results confirmed that the stereoselectivity of the reaction to form the trans-isomer product is more favorable than the cis-isomer, and the calculated trans/cis ratio is in accordance with the experiment. Moreover, the conceptual density functional theory reactivity indices suggest that the electronic effect controls the regioselectivity. What is more, the stereoselectivity analyzed by weak non-covalent interaction also shows the importance of electronic effect. Graphical Abstract.

Theoretical prediction of the impact sensitivities of energetic C-nitro compounds.

In order to design high-energetic and insensitive explosives, the frontier orbital energy gaps, surface electrostatic potentials, nitro group charges, bond dissociation energies (BDEs) of the C-NO2 trigger bonds, and intermolecular interactions obtained by the M06-2X/6-311++G(2d,p) method were quantitatively correlated with the experimental drop hammer potential energies of 10 typical C-nitro explosives. The changes of several information-theoretic quantities (ITQs) in the density functional reactivity theory were discussed upon the formation of complexes. The BDEs in the explosives with six-membered ring are larger than those with five-membered ring. The frontier orbital energy gaps of the compounds with benzene ring are larger than those with N-heterocycle. The models involving the intermolecular interaction energies and the energy gaps could be used to predict the impact sensitivity of the C-nitro explosives, while those involving ΔSS, ΔIF, and ΔSGBP are invalid. With the more and more ITQs, the further studies are needed to seek for a good correlation between impact sensitivity measurements and ITQs for the energetic C-nitro compounds. The origin of sensitivity was revealed by the reduced density gradient method.

Hydration and swelling: a theoretical investigation on the cooperativity effect of H-bonding interactions between p-hydroxy hydroxymethyl calix[4]/[5]arene and H2O by many-body interaction and density functional reactivity theory.

In order to explore the nature of the hydration and swelling of superabsorbent resin, a theoretical investigation into the cooperativity effect of the H-bonding interactions in the hydrates of four model compounds that can be regarded as the units of hydroquinone formaldehyde resin (HFR) (i.e., O-hydroxymethyl-1,4-dihydroxybenzene, methylene di-O-hydroxymethyl-1,4-dihydroxybenzene, p-hydroxy hydroxymethyl calix[4]arene and p-hydroxy hydroxymethyl calix[5]arene) was carried out by many-body interaction and density functional reactivity theory. The HFR···H2O···H2O complexes, in which the H2O···H2O moieties are bound with both the hydroxyl groups of HFR, are the most stable. For the HFR(H2O)n clusters, the interaction energy per building block is increased as the number of the size n increases, indicating the cooperativity effect. Therefore, a deduction is given that the cooperativity effects of the H-bonding interactions play an important role in the process of the hydration and swelling of HFR, and the swelling behavior is mainly attributed to the cooperativity effects which arised from the interactions between the H2O molecules. The origin of the cooperativity effect was examined employing several information-theoretic quantities in the density functional reactivity theory. The degree of swelling of HFR was quantitated using a measure of volume. Graphical abstract.

Validation of Hammett's Linear Free Energy Relationship Through an Unconventional Approach.

The present study tries to validate Hammett's linear free energy relationship through an unconventional approach based on the density functional reactivity theory (DFRT). A kinetic energy component [ΔEB(A)], derived from the DFRT-based comprehensive decomposition analysis of stabilization energy scheme, is used to verify the linear nature of Hammett's log(kX/kH) versus σ plot. The study shows that the [Formula: see text] versus σ plot (where -X is the atom or group substituted in place of -H) is linear in nature (with reasonably high correlation coefficient values) for different series of reactions. The slopes of the plots also reveal the electrophilic or nucleophilic nature of the transition states as is obtained from the conventional log(kX/kH) versus σ plot. The study thus establishes that the DFRT-based energy component ΔEB(A) (which is very easy to compute) can be used, instead of k-values, obtained either from the experiment or from computationally intensive conventional thermochemistry calculations to generate reliable Hammett's plot.

Theoretical Analysis of the Regioselective Electrophilic Chloration and Chemioselective Esterification of the pyrazolo[1,5-a]pyridine-2,3-dicarboxylic acid

The reaction between the pyrazolo[1,5-a]pyridine-2,3-dicarboxylic acid 1 and SOCl 2 has been studied within the Density Functional Theory (DFT) B3LYP/6-31G(d,p) computational level. Examination of the conceptual DFT reactivity indices permit the elucidation of the reactivity, and the regio- and chemoselectivity experimentally observed. The possible regioselective channels and chemoselective channels were explored and characterized. Analysis of the energies associated with the different reaction pathways shows that this reaction is completely chemioselective and regioselective, in conformity with the experimental results.

Push-pull nitronates in the [3+2] cycloaddition with nitroethylene: Molecular Electron Density Theory study

The structure and the participation of the N-methoxy-N-[bis(methoxycarbonyl)methylene]amine N-oxide as model push-pull nitronate 1 with nitroethylene 2 in [3 + 2] cycloaddition (32CA) reaction have been analyzed within the Molecular Electron Density Theory (MEDT) using Density Functional Theory (DFT) calculations at the B3LYP(PCM)/6-31G(d) level. Topological analysis of the Electron Localization Function (ELF) of nitronate 1 reveals that this compound has pseudoradical center, while the conceptual DFT reactivity indices characterizes this three-atom-component (TAC) as a strong electrophile. The analyzed 32CA reaction takes place through a one-step mechanism. A Bonding Evolution Theory (BET) study of the more favorable reaction path associated with the 32CA reaction of nitronate 1 with nitroethylene 2 indicates that it is associated with a non-concerted two-stage one-step mechanism, in which the activation energy is mainly related with to the initial formation of the O3–C4 single bond. In the case of this reaction, an additional mechanism with formation of intermediate 7 is also found.

Hexamethylphosphanetriamine‐mediated aziridination of imines with alpha‐ketoesters: A molecular electron density theory study

AbstractThe highly trans‐stereoselective reaction of oxyphosphonium enolate (OPE) with N‐benzylidene‐4‐methoxybenzenesulfonamide (N‐BMS) in toluene, at room temperature leading to trans‐aziridine‐2‐carboxylate (trans‐Az 3), was theoretically studied using molecular electron density theory (MEDT) at the B3LYP/6‐31G(d) computational level to shed light on the energy transformation, selectivities, and mechanistic aspects. This domino process is initialized by adding of N,N,N′,N′,N″,N″‐hexamethylphosphanetriamine (HMPT) to methyl benzoylformate to generate OPE. Subsequently, nucleophilic addition of OPE to the C–N double bond in N‐BMS leads to the intermediate IN‐Ta. Finally, trans‐Az 3 is formed through a 3‐exo‐tet ring closure step as a result of the nucleophilic attack of the negatively charged nitrogen atom on the carbon atom bearing –OP (NMe2)3 in IN‐Ta. Analysis of the relative Gibbs free energies shows that the ring closure step is the rate‐determining step. By an investigation of the conceptual density functional theory reactivity indices, OPE and N‐BMS are classified as a strong nucleophilic and as a strong electrophilic species, respectively, which indicates that the additional step of OPE to N‐BMS should display a high‐polar character. An analysis of the calculated electrophilic and nucleophilic Parr functions at the reactive sites of reagents clarifies the regioselectivity observed experimentally along the C1–C2 bond formation process.

Correlation between Equilibrium Constant and Stabilization Energy: A Combined Approach Based on Chemical Thermodynamics, Statistical Thermodynamics, and Density Functional Reactivity Theory.

In the present work, an attempt is made to establish the correlation between equilibrium constant and stabilization energy [ΔESE(AB)] generated from density functional reactivity theory (DFRT). The reactions chosen here are of type A + B ⇌ AB (i.e., adduct formation type) between an electron acceptor, A, and an electron donor, B. The representative acceptors are methyltrioxorhenium (MTO) and substituted benzaldehydes whereas donors are 26 mono- and bidentate ligands (having N-donors) and semicarbazide. The trends of experimentally generated equilibrium constant (K) values match with those of ΔESE(AB) in most of the cases, both in gas phase as well as in solvent. Justification of this reliable correlation is provided analytically using the expressions of standard Gibbs free energy of reaction (i.e., ΔrGθ) and the stabilization energy expression generated by DFRT. A further analytical explanation (albeit not very rigorous) is provided through statistical thermodynamics showing how equilibrium constant (K) is related to ΔESE(AB) for reactions of the type A + B ⇌ AB, where either A or B is a common species.