DFT mechanistic study of the chemical fixation of CO2 by aziridine derivatives.

Using density functional theory (DFT), we treat the reaction of coupling of CO2 with aziridine in gas phase, in the presence of water and of a green catalyst (NaBr). Computations show that, in gas phase, this ring-opening conversions to oxazolidinones initiates by coordinating a CO2 molecule to the nitrogen atom of the aziridine. Then, a nucleophilic interaction between one oxygen atom of the coordinated CO2 and the carbon atom of the aziridine occurs. For methyl substituted aziridine, two pathways are proposed leading either to 4-oxazolidinone or to 5-oxazolidinone. Besides, we show that the activation energy of this reaction reduces in aqueous solution, in the presence of a water molecule explicitly or NaBr catalyst. In addition, the corresponding reaction mechanisms and regioselectivity associated with this ring-opening conversions to oxazolidinones, in the presence of carbon dioxide are found to be influenced by solvent and catalyst. The present findings should allow better designing regioisomer oxazolidinones relevant for organic chemistry, medicinal and pharmacological applications.

Chalcogen Noncovalent Interactions between Diazines and Sulfur Oxides in Supramolecular Circular Chains.

The noncovalent chalcogen interaction between SO2/SO3 and diazines was studied through a dispersion-corrected DFT Kohn-Sham molecular orbital together with quantitative energy decomposition analyses. For this, supramolecular circular chains of up to 12 molecules were built with the aim of checking the capability of diazine molecules to detect SO2/SO3 compounds within the atmosphere. Trends in the interaction energies with the increasing number of molecules are mainly determined by the Pauli steric repulsion involved in these σ-hole/π-hole interactions. But more importantly, despite the assumed electrostatic nature of the involved interactions, the covalent component also plays a determinant role in its strength in the involved chalcogen bonds. Noticeably, π-hole interactions are supported by the charge transfer from diazines to SO2/SO3 molecules. Interaction energies in these supramolecular complexes are not only determined by the S···N bond lengths but attractive electrostatic and orbital interactions also determine the trends. These results should allow us to establish the fundamental characteristics of chalcogen bonding based on its strength and nature, which is of relevance for the capture of sulfur oxides.

σ-Hole intermolecular interactions between carbon oxides and dihalogens: Ab-initio investigations.

Recently, halogen bonding (XB) has received increased attention as a new type of non-covalent interaction widely present in nature. In this work, quantum chemical calculations at DFT level have been carried out to investigate halogen bonding interactions between COn (n = 1 or 2) and dihalogen molecules XY (X = F, Cl, Br, I and Y = Cl, Br, I). Highly accurate all-electron data, estimated by CCSD(T) calculations, were used to benchmark the different levels of computational methods with the objective of finding the best accuracy/computational cost. Molecular electrostatic potential, interaction energy values, charge transfer, UV spectra, and natural bond orbital (NBO) analysis were determined to better understand the nature of the XB interaction. Density of states (DOS) and projected DOS were also computed. Hence, according to these results, the magnitude of the halogen bonding is affected by the halogen polarizability and electronegativity, where for the more polarizable and less electronegative halogen atoms, the σ-hole is bigger. Furthermore, for the halogen-bonded complexes involving CO and XY, the OC∙∙∙XY interaction is stronger than the CO∙∙∙XY interaction. Thus, the results presented here can establish fundamental characteristics of halogen bonding in media, which would be very helpful for applying this noncovalent interaction for the sustainable capture of carbon oxides.

DFT Study of Regio- and Stereoselective 13DC Reaction between Diazopropane and Substituted Chalcone Derivatives: Molecular Docking of Novel Pyrazole Derivatives as Anti-Alzheimer's Agents.

In the present work, a combination of experimental and density functional theory (DFT) investigation of the (3+2) cycloaddition reactions of diazopropane with chalcone derivatives was reported. All calculations were performed using several DFT approaches (B3LYP, M06, M06-2X) and 6-311+G(d, p) basis set. Based on the NMR, MS analyses and IRC calculations, the pyrazole derivatives are the kinetic adducts over the oxadiazoles. The use of two equivalents of diazopropane leads to thermodynamical products. A molecular docking analysis was performed to investigate the efficiency of the obtained products against selected drug targets in anti-Alzheimer ligand-receptor interactions. We revealed that the ligands selected were bound mainly to the catalytic (CAS) and peripheral (PAS) anionic sites of acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) inhibitors, respectively. The selected ligands 1, 3, 4 and P14 may act as the best inhibitors against Alzheimer's disease (AD).

Chemosensing Properties of Coumarin Derivatives: Promising Agents with Diverse Pharmacological Properties, Docking and DFT Investigation.

In this work, a three-component reaction of 3-acetyl-4-hydroxycoumarine, malononitrile, or cyanoacetate in the presence of ammonium acetate was used to form coumarin derivatives. The chemical structures of new compounds were identified by 1H, 13C NMR and an elemental analysis. These compounds were examined in vitro for their antimicrobial activity against a panel of bacterial strains. In addition, these compounds were investigated for antioxidant activities by superoxideradical, DPPH (2,2-Diphenyl-1-picrylhydrazyl), and hydroxyl radical scavenging assays, in which most of them displayed significant antioxidant activities. Furthermore, these compounds were evaluated for anti-inflammatory activity by indirect hemolytic and lipoxygenase inhibition assays and revealed good activity. In addition, screening of the selected compounds 2-4 against colon carcinoma cell lines (HCT-116) and hepatocellular carcinoma cell lines (HepG-2) showed that that 2-amino-4-hydroxy-6-(4-hydroxy-2-oxo-2H-chromen-3-yl)nicotinonitrile 4 exhibited good cytotoxic activity against standard Vinblastine, while the other compounds exhibited moderate cytotoxic activity. Docking simulation showed that2-amino-4-hydroxy-6-(4-hydroxy-2-oxo-2H-chromen-3-yl)nicotinonitrile 4 is an effective inhibitor of the tumor protein HCT-116. A large fluorescence enhancement in a highly acidic medium was observed, and large fluorescence quenching by the addition of traces of Cu2+ and Ni2+ was also remarked.

Silver-N-heterocyclic carbene complexes-catalyzed multicomponent reactions: Synthesis, spectroscopic characterization, density functional theory calculations, and antibacterial study.

Nowadays, silver-N-heterocyclic carbene (silver-NHCs) complexes are widely used in medicinal chemistry due to their low toxic nature toward humans. Due to the success of silver-NHCs in medicinal applications, interest in these compounds is rapidly increasing. Therefore, the interaction of N,N-disubstituted benzimidazolium salts with Ag2 O in dichloromethane to prepare novel Ag(I)-NHCs complexes was carried out at room temperature for 120 h in the absence of light. The obtained complexes were identified and characterized by 1 H and 13 C nuclear magnetic resonance, Fourier-transform infrared, UV-Vis, and elemental analysis techniques. Then, the silver complexes were applied for three-component coupling reactions of aldehydes, amines, and alkynes. The effect of changing the alkyl substituent on the NHCs ligand on the catalytic performance was investigated. In addition, it has been found that the complexes are antimicrobially active and show higher activity than the free ligand. The silver-carbene complexes showed antimicrobial activity against specified microorganisms with MIC values between 0.24 and 62.5 µg/ml. These results showed that the silver-NHC complexes exhibit an effective antimicrobial activity against bacterial and fungal strains. A density functional theory calculation study was performed to identify the stability of the obtained complexes. All geometries were optimized employing an effective core potential basis, such as LANL2DZ for the Ag atom and 6-311+G(d,p) for all the other atoms in the gas phase. Electrostatic potential surfaces and LUMO-HOMO energy were computed. Transition energies and excited-state structures were obtained from the time-dependent density functional theory calculations.

Electronic structure and optical properties of isolated and TiO2 -grafted free base porphyrins for water oxidation: A challenging test case for DFT and TD-DFT.

Seven free base porphyrins employed in dye-sensitized photoelectrosynthetic cells are investigated with the aim of benchmarking the ability of different density functional theory (DFT) and time-dependent DFT approaches in reproducing their structure, vertical, and E0-0 excitation energies and the energy levels alignment (red-ox properties) at the interface with the TiO2 . We find that both vertical and E0-0 excitation energies are accurately reproduced by range-separated functionals, among which the ωB97X-D delivers the lowest absolute deviations from experiments. When the dye/TiO2 interface is modeled, the physical interfacial energetics is only obtained when the B3LYP functional is employed; on the other hand, M06-2X (54% of exchange) and the two long-range corrected approaches tested (CAM-B3LYP and ωB97X-D) excessively destabilize the semiconductor conduction band levels with respect to the dye's lowest unoccupied molecular orbitals (LUMOs), predicting no pathway for electron injection. © 2019 Wiley Periodicals, Inc.

Synthesis, characterization, optical properties, biological activity and theoretical studies of a 4 nitrobenzylidene) amino) phenyl)imino)methyl)naphthalen-2-ol -based fluorescent Schiff base.

A new Schiff base, 1-(E)-(4-((E) 4nitrobenzylidene) amino) phenyl)imino) methyl)naphthalen-2-ol (4NMN), was prepared from the reaction of p-phenylenediamine with 2-hydroxy-1-naphthaldehyde and 4-nitrobenzaldehyde and characterized with spectroscopic analysis. UV-VIS and NMR. Frontier molecular orbitals, molecular electrostatic potential, and chemical reactivity descriptors of the synthesized compound were studied using molecular modeling methods. The antibacterial and antifungal activities of the Schiff base were studied for its minimum inhibitory concentration. The compound showed a higher effect on yeast than against bacteria. Density functional theory (DFT) calculations were performed to study the mechanism of reaction for the synthesis of 4NMN, and the results were consistent with the experimental findings. 4NMN exhibited moderate antibacterial and antifungal activities and demonstrated higher inhibition potential against different resistant strains compared to the reference drug gentamycin. The absorption and fluorescence spectra of 4NMN were measured in different solvents, and the effect of relative polarity and acidity on the medium was observed. An inner filter effect was observed at high concentrations, and the compound showed considerable fluorescence enhancement with increasing medium viscosity and fluorescence quenching by the addition of traces of Cr1+ and Cu2+. Additionally, molecular docking studies were conducted to investigate the efficiency of antibacterial and antifungal targets.

Benzimidazole derivatives as a new scaffold of anticancer agents: Synthesis, optical properties, crystal structure and DFT calculations.

The absolute necessity to fight some class of tumour is perceived as serious health concerns, and the discovery and development of effective anticancer agents are urgently needed. So, the novel benzimidazole derivatives (2a-b) were designed, synthesized, with their structures rigorously characterized using single X-ray crystallography, FT-IR, UV, and NMR spectroscopy, alongside elemental analysis. The geometric structures were optimized using density functional theory (DFT) calculations performed at the ωB97X-D/cc-pVDZ level, yielding good agreement with experimental XRD data. The studied salt complexes exhibited the ability to absorb UV light at 275 nm. Furthermore, anticancer activity of the compounds was screened against (MDA-MB-231, MCF-7, HT-29 and healthy cell line (HF)) and revealed the remarkable efficacy of select newly synthesized Benzimidazole derivatives (2a-b). Compound 2a showed relative significant higher cytotoxicity (165.02) in MDA-MB-231 cancer cell line. This underscores their promising potential in therapeutic applications, affirming their role as valuable contenders in the pursuit of novel anticancer agents.

Porphyrin and phthalocyanine heavy metal removal: overview of theoretical investigation for heterojunction organic solar cell applications.

CONTEXT: Heavy metals are highly noxious, and their presence can cause diverse effects on living organisms and the environment. Crown ether porphyrins and phthalocyanines are known to effectively extract these pollutants and are also used in photovoltaic devices. This study aims to evaluate various factors that govern intramolecular charge transfer (ICT) and photo-injection processes, including maximum absorption wavelength (λmax), density of states (DOS), charge transfer dipole (µCT), light harvesting efficiency (LHE), open-circuit voltage (Voc), and free energy change of electron injection (ΔGinj) in order to investigate the performance of different compounds designed from metalloporphyrins for bulk-heterojunction organic solar cell (BHJ-OSC) applications. The porphyrin complex showed the best optoelectronic properties, with remarkable LHE values and CT amounts compared to phthalocyanine derivatives. The central metal played a significant role in optimizing the optical properties of the materials for use in solar cells. HgPr4O and CdPr4O were found to have optimal Voc values, resulting in effective injection, high electron, and hole mobilities, making them ideal materials for highly efficient BHJ-OSC devices. METHODS: Density functional theory (DFT) approach was employed with the B3LYP functional and the def2TZVP basis set as implemented in the Gaussian 16 revision C.01 program to investigate the designed complexes and to compute geometrical parameters, frontier molecular orbitals (FMOs), and natural bond orbital (NBO). Furthermore, the time-dependent density functional theory (TD-DFT) method was used to analyze the optical properties and photovoltaic characteristics of selected metalloporphyrins by examining the UV-Vis spectra. In summary, the study presents a thorough description of the structural and electronic properties of the investigated complexes and provides insights into their potential use in photovoltaic applications.

Metallo-dithiaporphyrin pigments for bulk-heterojunction solar cell applications: ab initio investigation of structural and optoelectronic properties.

Metallo-dithiaporphyrin small molecules have been designed by substituting Ru(ii) with various transition metals at the same oxidation state (M = Mn, Fe, Ni, Cu) as donor materials for Bulk Heterojunction Organic Solar Cells (BHJ-OSCs). Density functional theory (DFT) and time-dependent DFT (TD-DFT) have been used to study the optoelectronic properties of metallo-dithiaporphyrin at various functionals and basis sets. We discovered that the open-circuit voltage (VOC) value increases when Ru(ii) in Ru(S2TTP)Cl2 (S2TTP = tetra-p-tolyldithiaporphyrin) is substituted. In addition, the light harvesting efficiency (LHE) of nickel, manganese, and iron complexes was found to be similar to that of ruthenium, and the iron complex furthermore presented a comparable charge transfer in the excited state corresponding to the Q-band, compared to Ru(S2TTP)Cl2. Hence M(S2TTP)Cl2 (M = Mn, Fe, Ni) appear to be potential low cost candidate donor molecules within a bulk heterojunction solar cell. We further propose suitable engineered acceptor pigments, fitted to provide a good overall solar cell efficiency.

Regio- and stereoselectivity of the [3+2] cycloaddition of nitrones with methyl-acetophenone: A DFT investigation.

A theoretical study of the regio- and stereoselectivities of the [3 + 2] cycloaddition reactions of nitrones with substituted alkene (methyl acetophenone) is investigated using density functional theory (DFT) and carried out at B3LYP/6-311+G(d,p) level. The reactivity of these cycloadditions is rationalized by FMO model, activation energy calculations, and philicity indexes. The electronic populations have been calculated from natural orbital, which based on charges by using NBO analysis, MK and CHelpG electrostatic population. The four possible pathways, fused and bridged regioisomeric modes, and the two stereoisomeric approaches endo and exo for the cycloaddition reactions are analyzed and discussed. Analysis of TS geometries and bond lengths demonstrate that these reactions follow a one-step mechanism with asynchronous transition states. The activation energy indicated a favored endo approach along the four reaction pathways.

DFT investigation of solvent, substituent, and catalysis effects on the intramolecular Diels-Alder reaction.

In this study, we report on a DFT investigation of two intramolecular Diels-Alder furan reactions. Optimizations of the studied structures, TS and IRC calculations, were carried out at B3LYP/6-31G(d) level. We have studied the effect of substituent, solvent and Lewis acid catalyst on cyclization-retrocyclization equilibria, activation energies, and stability of the desired products. The analysis of orbital coefficients, IRC curves, and Wiberg indices have proved that both reactions are under orbital control. We have found that for the reaction I (2↔4 + 5), where R = H, the exo attack is favored by hydrogen bond interaction, while for R = t-Bu, the steric hindrance leads to the endo attack. For the reaction II (3 → 6 + 7), the t-Bu-substituted products are the most stable ones. At another level, we have found that it is recommended to use polar organic solvents as DMSO with Lewis acid catalyst BF3. The latest leads to accelerate the reaction II with stabilization of the desired products.

Ethyl 3-[1-(5,5-dimethyl-2-oxo-1,3,2-dioxaphosphorin-2-yl)propan-2-ylidene]carbazate: a combined X-ray and density functional theory (DFT) study.

In the title compound, C(11)H(21)N(2)O(5)P, one of the two carbazate N atoms is involved in the C=N double bond and the H atom of the second N atom is engaged in an intramolecular hydrogen bond with an O atom from the dimethylphosphorin-2-yl group, which is in an uncommon cis position with respect to the carbamate group. The cohesion of the crystal structure is also reinforced by weak intermolecular hydrogen bonds. Density functional theory (DFT) calculations at the B3LYP/6-311++g(2d,2p) level revealed the lowest energy structure to have a Z configuration at the C=N bond, which is consistent with the configuration found in the X-ray crystal structure, as well as a less stable E counterpart which lies 2.0 kcal mol(-1) higher in potential energy. Correlations between the experimental and computational studies are discussed.

Reactivity of pyrazole derivatives with halomethanes: A DFT theoretical study.

The N-alkylation reaction of pyrazole derivatives with halomethanes was studied using density functional theory (DFT). The hybrid method B3LYP was employed, along with an ECP basis set such as LANL2DZ for halogen atoms (X = Cl, Br, I) and the 6-311 + G(d,p) basis set for all other atoms. In order to predict the specific site at which the pyrazole derivatives interact with halomethanes, local reactivity descriptors such as the Fukui functions were calculated. Detailed analysis of transition-state energies showed that alkylation occurred at the nitrogen atom N2 in the pyrazole derivatives, in agreement with the chemical reactivity results. The reaction mechanisms were elucidated by performing intrinsic reaction coordinate (IRC) calculations that considered the effects of the solvent and the species of halogen in the halomethane.

A Short Route to the Ester (±) HomoSarkomycin via Johnson-Claisen Rearrangement.

BACKGROUND: α-Methylene cycloalkanones are considered of interest because of their biological activity. Herein, in this paper the synthesis of (±) HomoSarkomycine Esters was described and characterized. METHODS: Using Bylis-Hillman adducts, triethlorthoacetate and propanoic acid, (±) HomoSarkomycine Esters could be synthesized by smoothly Johnson-Claisen rearrangement. RESULTS: A small library of target compounds was prepared under optimized reaction conditions in moderate yields. The reaction mechanism and the DFT study have been investigated. CONCLUSION: This methodology provides ready access to 2-hydroxymethyl-2-cyclopentenone 1a which can be served as the raw materials of the synthesis of (±) HomoSarkomycine Ester.

Theoretical investigations on the mechanistic pathway of the thermal rearrangement of substituted N-acyl-2,2-dimethylaziridines.

The mechanism of the thermal rearrangement of substituted N-acyl-2,2-dimethylaziridines 1 has been studied using quantum chemistry methods. Geometries of reactants, transition states and products have been optimized at the B3LYP/6-311++G(2d,2p) level. Relative energies for various stationary points have been determined and reaction identified by IRC calculations. The results show that thermal rearrangements occur in three ways. Firstly, the transition state TS 1 in which a hydrogen atom of methyl groups migrates from primary carbon to oxygen of amid group to give the N-methallylamide 2. The second is via the transition state TS 2 in which the attack of oxygen to the tertiary carbon yields the oxazoline 3. The third is via the transition state TS 3 in which a hydrogen migrate from the secondary carbon to oxygen to give the vinylamide 4. In order to get insights into the factors determining the exact nature of its interactions with electrophiles, the application of reactivity parameters derived from density functional theory in a local sense, in particular the softness and Fukui function, to interpret and predict the mechanisms of the thermal decomposition of the N-acyl-2,2-dimethylaziridines 1, has been discussed.