DFT Calculated Research Articles

Synthesis of 1,2-Bis(2-aryl-1H-indol-3-yl)ethynes via 5-exo-Digonal Double Cyclization Reactions of 1,4-Bis(2-isocyanophenyl)buta-1,3-diyne with Aryl Grignard Reagents.

New π-conjugated 1,2-bis(2-aryl-1H-indol-3-yl)ethynes 1a-j having various substituents on the two aryl groups were efficiently synthesized via unusual 5-exo-digonal double isocyanide-acetylene cyclization reactions of 1,4-bis(2-isocyanophenyl)buta-1,3-diyne 3 and aryl Grignard reagents (R-MgBr, R = C6H5 (1a), 4-H3CC6H4 (1b), 2-H3CC6H4 (1c), 3-MeOC6H4 (1d), 3-(CH3)2NC6H4 (1e), 4-F3CC6H4 (1f), 4-FC6H4 (1g), 3-FC6H4 (1h), 4-PhOC6H4 (1i), and 2-Naph (1j)) in 19-85% yields. The UV-vis spectra were rationalized in detail using time-dependent DFT and single point calculations. The fluorescence emission peaks for 1a-j were observed at around 450 nm. Especially for 1f and 1j, those spectra displayed broad emission bands and relatively large Stokes shifts (3977-4503 cm-1), indicating the contribution of an intramolecular charge transfer. The absolute quantum yields (0.50-0.62) of 1a-j were higher than those of parent 8 (0.19) and 2-phenyl-1H-indole (0.11). The electrochemical features for 1a-j were investigated by cyclic voltammetry. The frontier molecular orbital levels for 1a-j were estimated based on the combination of oxidation potentials, UV-vis, and DFT calculated data. The structural property of 1,2-bis(2-phenyl-1H-indol-3-yl)ethyne 1a was characterized by several spectroscopic methods and finally determined by X-ray analysis of a single crystal of 1a recrystallized from ethyl acetate. The structural features of 1a-j were also supported by DFT calculations.

Absolute configuration of diterpenoids from Jatropha dioica by vibrational circular dichroism

The absolute configuration of jatropholone A 1 and B 2, including the possibility to observe the vibrational circular dichroism (VCD) capacity to differentiate between two epimeric compounds in the presence of an inherently dissymmetric chromophore, which normally dominates VCD and electronic circular dichroism (ECD) spectra, followed after comparison of their experimental and DFT calculated VCD spectra, allowed us to conclude that although non-local (M/P) chirality generated by atropisomerism dominates over local chirality generated by an (R/S) change, the stereogenic center can confidently be assigned by VCD after DFT calculations. In addition, the absolute configurations of jatrophatrione 3 and citlalitrione 4, a compound proposed as a taxonomic marker for the genus Jatropha, were assigned by contrasting their respective calculated and experimental IR and VCD spectra. The evaluation of Flack and Hooft parameters obtained from the single-crystal X-ray diffraction data of jatropholone B acetate 6, and of 4 independently confirmed the absolute configurations of these molecules.

Interplay Between Chemistry and Morphology of the Catalytic Layer in Platinum Group Metal-Free Cathodes

Among the different Fuel Cell technologies, one is based on the implementation of Polymer Electrolyte Membrane fuel cells (PEMFC). Significant research effort has been directed towards replacement of the platinum by materials mainly consisting of metal–nitrogen–carbon (MNC) network. The knowledge derived from tens of years of optimization of Pt-based PEMFC can not be directly translated to MNC catalytic systems due to different approaches in making catalyst layers. The structure of the active site/sites of the PGM-free ORR electrocatalysts remains contentious even after 50 years of research. The structure of the active site within the Membrane Electrode Assembly (MEA) has not been studied at all. It is necessary to understand the effect of the interaction of ionomer and catalyst on the structure of the active site, morphology of catalyst layer and durability. There is a missing link between durability and activity parameters as well as chemical and morphological changes that occur inside the catalyst layer during the oxygen reduction reaction in a fuel cell. In this study, we are investigating a series of MNC electrocatalysts synthesized by the same sacrificial support route[1] and their performance in MEA. Chemistry of the electrocatalysts and catalyst layers is studied by XPS. The types of nitrogen and iron-nitrogen functionalities that are present in these materials are in-plane defects such as graphitic N and N-coordinated to three or four nitrogens and a multitude of possible edge sites such as pyridinic, pyrrolic, quaternary and Fe-N2/Fe-N sites. [2, 3] In the catalyst layers, the makeup of the active site may be affected by the interactions with negatively charged sulfonate group of nafion. Due to this interaction between groups on the catalyst surface and sulfonate groups of nafion, the rearrangement in high binding energy range has been observed. The higher relative amount of peaks between 401-403 eV in the catalyst layers is due to the shift in the position of other peaks due to interaction with an ionomer. DFT calculations were used to evaluate the strength of the interaction between different types of nitrogen containing defects and sulfonate groups and to calculate binding energy shifts of N 1s spectra upon ionomer binding. [4] Figure 1 shows DFT calculated adsorption energies of sulfonate groups on nitrogen defects. High adsorption energies particularly for protonated nitrogens which may be either pyrrolic or protonated pyridine nitrogen is observed. Moreover, the higher amount of protonated nitrogens in catalyst layer results in worse MEA performance. The pore structure is critical to the transport of oxygen to active sites and removal of water. The change in pore structure induced by the chemical changes introduced during fuel cell operation has to be understood in order to design PGM-free electrocatalyst with highest possible lifetime. The morphology of catalyst layers will be analyzed by focused ion beam/scanning electron microscopy (FIB-SEM) sectioning. This will allow to obtain a 3D visual representation of morphology of catalysts layers and to estimate in detail the evolution of structural parameters such as: specific surface area, total porosity, connectivity of pores and others as a result of degradation studies. 1. Serov, A., et al., Nano-structured non-platinum catalysts for automotive fuel cell application. Nano Energy, 2015. 16: p. 293-300. 2. Jia, Q., et al., Spectroscopic Insights into the Nature of Active Sites in Iron-Nitrogen-Carbon Electrocatalysts for Oxygen Reduction in Acid and the Redox Mechanisms. Nano Energy, 2016. 3. Artyushkova, K., et al., Chemistry of Multitudinous Active Sites for Oxygen Reduction Reaction in Transition Metal-Nitrogen-Carbon Electrocatalysts. Journal of Physical Chemistry C, 2015. 119(46): p. 25917-25928. 4. Kabir, S., et al., Binding energy shifts for nitrogen-containing graphene-based electrocatalysts – experiments and DFT calculations. Surface and Interface Analysis, 2016. Figure 1

Synthesis and electrochemical characterization of oligothiophenes with 1,2,4-triazine and 5,5′-bi-1,2,4-triazine as strong electron acceptor units

Two series of 1,2,4-triazine and 5,5′-bi-1,2,4-triazine-based oligothiophene derivatives have been developed and their molecular structures were confirmed by X-ray analysis. Electrochemical, spectroelectrochemical and spectral measurement were used to estimate their properties. The results show that the optical and electronic properties can be tuned over a broad range. The conjugation of two 1,2,4-triazine units leads to a significant strengthening of their electron-accepting properties in contrary to some widely used electron-acceptor units. The comparison of electrochemically estimated and DFT calculated electron affinity (EA) of oligothiophenes with 5,5′-bi-1,2,4-triazine and 1,2,4-triazine units indicates that conjugation of two triazine units leads to the formation of strong electron acceptor moiety with electrochemically estimated EA equal to 4 eV. Electron paramagnetic resonance spectra recorded during electrochemical reduction reveals the delocalization of radical mainly at 5,5′-bi-1,2,4-triazine core in contrary to 1,2,4‐triazine derivatives where thiophene arm is also involved. DFT calculations support the experimental results. These results indicate that obtained materials especially with 5,5′-bi-1,2,4-triazine units can be tested as n-type semiconductors for wide range of organic optoelectronic applications.

The separation mechanism of Am(iii) from Eu(iii) by diglycolamide and nitrilotriacetamide extraction reagents using DFT calculations.

Relativistic density functional calculations were applied to study the separation behaviors of the Am(iii) ion from the Eu(iii) ion by diglycolamide (DGA) and nitrilotriacetamide (NTA) ligands in order to understand the difference in the separation mechanism of their reagents. The complexation reaction was modeled on the basis of previous experimental studies. The calculated energies based on stabilization by complex formation at the ZORA-B2PLYP/SARC level predicted that the DGA reagent preferably coordinated to the Eu(iii) ion when compared with the Am(iii) ion. In contrast, the NTA reagent selectively coordinated to the Am(iii) ion when compared with the Eu(iii) ion. These results reproduced the experimental selectivity of DGA and NTA ligands toward Eu(iii) and Am(iii) ions. Mulliken's population analyses implied that the difference in the contribution of the bonding property between the f-orbital of Am and donor atoms determined the comparative stability of Eu and Am complexes.

Crystal structure, DFT study, and Hirshfeld surface analysis of ethyl 5-(3,4-dimethoxyphenyl)-7-methyl-3-phenyl-5H-thiazolo[ 3,2-A]pyrimidine-6-carboxylate

The structural characterization of fused thiazolopyrimidine 1 (C24H24N2O4S) is performed using the single crystal X-ray study, the DFT calculation, and the Hirshfeld surface analysis. The molecular packing of the crystal is mainly stabilized by C–H…O and C–H…π interactions. A DFT calculated HOMO-LUMO energy gap of 3.90 eV indicates a high kinetic stability of the compound. The 3D Hirshfeld surfaces and the associated 2D fingerprint plots are investigated for short contact interactions. The relative contribution of different interactions to the Hirshfeld surface indicates that the H…H, C…H, and O…H contacts account for about 83.4% of the total Hirshfeld surface area.

Stereochemistry of 3-isopropoxy-3-methyl-1,3-oxasilinane–the first 3-silatetrahydropyran with an exo-cyclic RO–Si bond

Molecular structure and conformational behavior of 3-isopropoxy-3-methyl-3-oxasilinane is studied by low temperature 13C NMR spectroscopy and theoretical calculations (DFT, MP2). Two conformers, 1-ROax and 1-ROeq, were found experimentally and located on the potential energy surface. LT 13C NMR spectroscopy gives almost equal population of the two conformers at 98 K with ΔG°98K=0.02 kcal/mol in favor of 1-ROax and ΔG#98K=4.5 kcal/mol. The corresponding DFT calculated values (ΔG°98K=0.03 kcal/mol, ΔG#98K=5.1 kcal/mol) are in excellent agreement with the experiment. Detailed DFT and MP2 calculations of the solvent effect on the conformational equilibrium were performed and highlighted the leveling out of the two conformers when transferred from gas to solution.

Synthesis, spectral and structural studies on some new isonicotinic thiosemicarbazide complexes and its biological activity

Complexes of Co(II), Ni(II) and Cu(II) with the new N-ethyl-2-isonicotinoylhydrazine carbothioamide (HEITsc) have been prepared. The complexes have been characterized by elemental analysis, molar conductance, spectral (IR, UV–Vis, ESR and mass), thermal (TG) and magnetic measurements. The IR spectra showed that HEITsc behaves as mononegative bidentate. According to the spectral data (UV–Vis and ESR) and magnetic measurements, different stereochemistries were proposed where both of Ni(II) and Co(II) complexes have octahedral while the Cu(II) has square planar geometry. The DFT calculation was used to optimize the geometric structure of the ligand its metal complexes. The minimum energy optimized structures were coincided with the proposed structures. The comparison of DFT calculated spectral data (IR and UV–Vis) with the experimental data showed a good agreement. Also, the ligand and metal complexes were examined as antimicrobial agents and the effect of these compounds on DNA degradation was studied.

Structural investigation of trifuoromethyl substituted bis(β-diketonato)-dichlorotitanium(IV) complexes displaying a mono-dinuclear equilibrium hydrolysis reaction

Mononuclear Ti(β-diketonato)2Cl2 complexes with CF3-containing β-diketonato ligands, exhibit a monomer-hydrolysed dinuclear complex equilibrium when dissolved in CDCl3 containing trace amounts of water. This result is in contrast to the more electron rich derivatives with non CF3-containing β-diketonato ligands, for example, Ti(acac)2Cl2, which exsists only as the monomer in CDCl3 solution. The X-ray structure of the μ-oxo bridged hydrolysed dinuclear complex {Ti(CF3COCHCOCH3)2Cl}2(μ-O) reveals that the two mononuclear Ti units forming the dinuclear structure, both adopt a cis-trans-cis configuration with the CF3 groups of the trifluoroacetylacetonate ligands in trans positions. In solution both mononuclear Ti(β-diketonato)2Cl2 and hydrolysed dinuclear {Ti(β-diketonato)2Cl}2(μ-O) complexes exist as equilibrium mixtures of isomers. DFT calculations, used to determine the stability of the isomers, showed that for monomeric bis(β-diketonato)-titanium(IV) complexes, there is agreement with experimental solid state structures, in that the most stable DFT calculated isomer, of a specific complex, formed in the solid state. However for the dinuclear {Ti(CF3COCHCOCH3)2Cl}2(μ-O) complex, DFT calculations revealed that although most of the 10 isomers are experimentally possible due to the small energy difference obtained between the isomers, an isomer of higher energy formed in the solid state, suggesting that the equilibrium reaction between the monomer and hydrolysed dinuclear complex may contribute to the formation of the less stable dinuclear isomer {Ti(CF3COCHCOCH3)2Cl}2(μ-O) (1111).

Palladium(ii) complexes bearing the 1,2,3-triazole based organosulfur/ selenium ligand: synthesis, structure and applications in Heck and Suzuki–Miyaura coupling as a catalyst via palladium nanoparticles

Air and moisture insensitive palladium complexes, [Pd(L)Cl2] (1/2), in which L = 1-benzyl-4-phenylthiomethyl or 1-benzyl-4-phenylselenomethyl-1H-1,2,3-triazole (L1 or L2) catalyze Heck (HC) and Suzuki–Miyaura coupling (SMC) reactions between a series of aryl bromides including deactivated bromides and n-butyl acrylate and phenylboronic acid, respectively. The optimal catalytic loading was found to be in the order of 0.01 mol%. HRTEM, TGA and EDX data indicated that 3–11 nm nanoparticles (NPs) composed of palladium and sulfur or selenium and protected with L or its fragment, were formed during the catalyzed reaction. The isolated NPs displayed catalytic activity and appeared to have a role in the catalysis. A two-phase test indicated that both homogeneous and heterogeneous catalysis took place. The complexes 1 and 2 were synthesized by the reactions of L1 and L2 respectively with [(MeCN)2PdCl2]. Their single crystal X-ray diffraction indicated that the geometry adopted by ligands around Pd in both complexes is distorted square planar with Pd–S and Pd–Se bond lengths of 2.2727(14) and 2.3693(8) Å, respectively. DFT calculation gave bond lengths and angles in keeping with the experimental values. The DFT calculated HOMO–LUMO energy difference is lower for 1 than for 2 in accordance with the observed higher catalytic activity of 1.

PH-Sensitive C–ON Bond Homolysis of Alkoxyamines of Imidazoline Series: A Theoretical Study

The pH-dependent kinetics of C-ON bond homolysis reactions of the four alkoxyamines (viz., the derivatives of 2-(4-(dimethylamino)-2-ethyl-5,5-dimethyl-2-(pyridin-4-yl)-2,5-dihydro-1H-imidazol-1-oxyl and 2-(2-carboxyethyl)-5,5-diethyl-2,4-dimethyl-2,5-dihydro-1H-imidazol-1-oxyl) in water solution have been scrutinized using DFT calculations (M06-2X/6-311++G(2df,p) level of theory with the PCM model). On the basis of computations, the experimental results obtained before (J. Org. Chem. 2011, 76, 5558) have been rationalized. The concentration dependence of all possible protonated forms of the four alkoxyamines was obtained from pH measurements. The contributions of particular protonated forms into the overall rate constants of thermolysis were estimated using the DFT calculated Gibbs free energies Δ(r)⁰G of C-ON bond homolysis reactions. The computations revealed that the observed rate constants of thermolysis of the two species at several pH values are dominated by decomposition reactions of two or even three protonated forms. The observed trends in reactivity of the alkoxyamines were mainly attributed to destabilization of the radical products of C-ON bond scission reactions. A linear correlation between the sum of radical stabilization energies (RSEs) of products of thermolysis and the calculated Gibbs free energies of reactions was found for various protonated forms of the species studied. Apart from this, the linear correlation exists between the relative RSE and nitrogen hyperfine constants aN of various protonated forms of the nitroxide radical products.

Lipophilicity Assessment of Ruthenium(II)-Arene Complexes by the Means of Reversed-Phase Thin-Layer Chromatography and DFT Calculations

The lipophilicity of ten ruthenium(II)-arene complexes was assessed by reversed-phase thin-layer chromatography (RP-TLC) on octadecyl silica stationary phase. The binary solvent systems composed of water and acetonitrile were used as mobile phase in order to determine chromatographic descriptors for lipophilicity estimation. Octanol-water partition coefficient, logK OW, of tested complexes was experimentally determined using twenty-eight standard solutes which were analyzed under the same chromatographic conditions as target substances. In addition, ab initio density functional theory (DFT) computational approach was employed to calculate logK OW values from the differences in Gibbs' free solvation energies of the solute transfer from n-octanol to water. A good overall agreement between DFT calculated and experimentally determined logK OW values was established (R 2 = 0.8024–0.9658).

Materials Design and Discovery with High-Throughput Density Functional Theory: The Open Quantum Materials Database (OQMD)

High-throughput density functional theory (HT DFT) is fast becoming a powerful tool for accelerating materials design and discovery by the amassing tens and even hundreds of thousands of DFT calculations in large databases. Complex materials problems can be approached much more efficiently and broadly through the sheer quantity of structures and chemistries available in such databases. Our HT DFT database, the Open Quantum Materials Database (OQMD), contains over 200,000 DFT calculated crystal structures and will be freely available for public use at http://oqmd.org . In this review, we describe the OQMD and its use in five materials problems, spanning a wide range of applications and materials types: (I) Li-air battery combination catalyst/electrodes, (II) Li-ion battery anodes, (III) Li-ion battery cathode coatings reactive with HF, (IV) Mg-alloy long-period stacking ordered (LPSO) strengthening precipitates, and (V) training a machine learning model to predict new stable ternary compounds.

Re and Br X-ray Absorption Near-Edge Structure Study of the Ground and Excited States of [ReBr(CO)3(bpy)] Interpreted by DFT and TD-DFT Calculations

X-ray absorption spectra of fac-[ReBr(CO)3(bpy)] near the Re L3- and Br K-edges were measured in a steady-state mode as well as time-resolved at 630 ps after 355 nm laser pulse excitation. Relativistic spin-orbit time-dependent density functional theory (TD-DFT) calculations account well for the shape of the near-edge absorption (the ″white line″) of the ground-state Re spectrum, assigning the lowest-lying transitions as core-to-ligand metal-to-ligand charge transfer from Re 2p(3/2) into predominantly π*(bpy) molecular orbitals (MOs) containing small 5d contributions, followed in energy by transitions into π* Re(CO)3 and delocalized σ*/π* MOs. Transitions gain their intensities from Re 5d and 6s participation in the target orbitals. The 5d character is distributed over many unoccupied MOs; the 5d contribution to any single empty MO does not exceed 29%. The Br K-edge spectrum is dominated by the ionization edge and multiple scattering features, the pre-edge electronic transitions being very weak. Time-resolved spectra measured upon formation of the lowest electronic excited state show changes characteristic of simultaneous Re and Br electronic depopulation: shifts of the Re and Br edges and the Re white line to higher energies and emergence of new intense pre-edge features that are attributed by TD-DFT to transitions from Re 2p(3/2) and Br 1s orbitals into a vacancy in the HOMO-1 created by electronic excitation. Experimental spectra together with quantum chemical calculations provide a direct evidence for a ReBr(CO)3 → bpy delocalized charge transfer character of the lowest excited state. Steady-state as well as time-resolved Re L3 spectra of [ReCl(CO)3(bpy)] and [Re(Etpy)(CO)3(bpy)](+) are very similar to those of the Br complex, in agreement with similar (TD) DFT calculated transition energies as well as delocalized excited-state spin densities and charge changes upon excitation.

Synthesis, optical power limiting, and DFT calculations of triplet–triplet absorption of three novel Pt(II)-diacetylide chromophores

Three novel rod-like Pt(II)-diacetylides have been synthesized. When subjected to intense laser light, all three compounds showed strong optical power limiting at 532 and 600nm. DFT calculated triplet–triplet electronic excitations were found to correlate with the nonlinear absorption.

Prodrugs for masking bitter taste of antibacterial drugs—a computational approach

DFT calculations for the acid-catalyzed hydrolysis of several maleamic acid amide derivatives revealed that the reaction rate-limiting step is determined on the nature of the amine leaving group. Further, it was established that when the amine leaving group was a secondary amine, acyclovir or cefuroxime moiety the tetrahedral intermediate formation was the rate-limiting step such as in the cases of acyclovir ProD 1- ProD 4 and cefuroxime ProD 1- ProD 4. In addition, the linear correlation between the calculated and experimental rates provided a credible basis for designing prodrugs for masking bitter taste of the corresponding parental drugs which have the potential to release the parent drug in a sustained release fashion. For example, based on the DFT calculated rates the predicted t₁/₂ (a time needed for 50 % of the reactant to be hydrolyzed to products) for cefuroxime prodrugs, cefuroxime ProD 1- ProD 4, were 12 min, 18 min, 200 min and 123 min, respectively.

Experimental and Theoretical Charge Density Distribution in a Host–Guest System: Synthetic Terephthaloyl Receptor Complexed to Adipic Acid

The experimental charge density distributions in a host-guest complex have been determined. The host, 1,4-bis[[(6-methylpyrid-2-yl)amino]carbonyl]benzene (1) and guest, adipic acid (2). The molecular geometries of 1 and 2 are controlled by the presence in the complex of intermolecular hydrogen bonding interactions and the presence in the host 1 of intramolecular hydrogen bonding motifs. This system therefore serves as an excellent model for studying noncovalent interactions and their effects on structure and electron density, and the transferability of electron distribution properties between closely related molecules. For the complex, high resolution X-ray diffraction data created the basis for a charge density refinement using a pseudoatomic multipolar expansion (Hansen-Coppens formalism) against extensive low-temperature (T = 100 K) single-crystal X-ray diffraction data and compared with a selection of theoretical DFT calculations on the same complex. The molecules crystallize in the noncentrosymmetric space group P2(1)2(1)2(1) with two independent molecules in the asymmetric unit. A topological analysis of the resulting density distribution using the atoms in molecules methodology is presented along with multipole populations, showing that the host and guest structures are relatively unaltered by the geometry changes on complexation. Three separate refinement protocols were adopted to determine the effects of the inclusion of calculated hydrogen atom anisotropic displacement parameters on hydrogen bond strengths. For the isotropic model, the total hydrogen bond energy differs from the DFT calculated value by ca. 70 kJ mol(-1), whereas the inclusion of higher multipole expansion levels on anisotropic hydrogen atoms this difference is reduced to ca. 20 kJ mol(-l), highlighting the usefulness of this protocol when describing H-bond energetics.

Microheterogeneities in Ionic‐Liquid–Methanol Solutions Studied by FTIR Spectroscopy, DFT Calculations and Molecular Dynamics Simulations

The interest in ionic liquids (ILs) is steadily increasing because of their fascinating physicochemical properties and because of their broad range of applications in synthesis, separation, catalysis and electrochemistry. However, the multiplicity of their uses strongly depends on a molecular understanding of their exceptional properties. One key to a better understanding of their unique properties are spectroscopic studies of ionic liquids in conventional organic solvents in combination with DFT calculations and molecular dynamics simulations. Therefore we investigated the mixtures of the imidazolium-based ionic liquid [C(2)mim][NTf(2)] with methanol. Caused by the amphiphilic character of methanol both liquids are miscible over the whole mixture range. The scope of this work is to study the changes in the IL network upon dilution and to investigate the formation of methanol clusters embedded in the IL matrix. The mixtures were studied by FTIR spectroscopy in the mid-infrared region. The formation of methanol clusters was studied from the OD stretching vibrational bands between 2300 and 2800 cm(-1). The cluster populations of methanol could be derived from molecular dynamics simulations for the same mixtures. Weighting the DFT calculated frequencies by the cluster populations we could reproduce the measured spectra in the OD stretching region up to X(MeOH)=0.5. Above X(MeOH)=0.8, strong formation of self-methanol clusters takes place resulting in increasing diffusion coefficients related to decreasing dynamical heterogeneities. Thus we obtained a deep understanding of the solute-solvent and solute-solute interactions as well as information about the presence of microheterogeneities in the mixtures.

A spectroscopic, electrochemical and DFT study of para-substituted ferrocene-containing chalcone derivatives: Structure of FcCOCHCH(p-tBuC6H4)

A comparative investigation of seven ferrocene-containing chalcones (Fc–CO–CHCH–C6H4R, with R=OCH3, CH3, Ph, tBu, H, Br and CF3) has been performed based on their electrochemical and spectroscopical behavior as well as with DFT calculations. These compounds were prepared by Claisen-Schmidt condensation of acetylferrocene and the appropriate benzaldehyde derivative. All compounds exhibited reversible chemical and electrochemical behavior, as confirmed by ΔE=83−93mV and ipc/ipa=0.93−1.00. The formal reduction potential E°′ for the compounds ranged between 231.0 and 261.5mV versus FcH/FcH+ as an internal standard. The UV–Vis spectra of all ferrocene-containing chalcones showed the characteristic peaks for aromatic systems at ±380nm and a peak in the visible region at ±490nm, which is attributed to the ferrocene moiety. FTIR of all the ferrocene-containing chalcones showed a characteristic CO stretching peak at ±1650cm−1. DFT calculated HOMO energies and ionization potentials correlate well with experimentally measured E°′ values.

Probing the reactivation process of sarin-inhibited acetylcholinesterase with α-nucleophiles: Hydroxylamine anion is predicted to be a better antidote with DFT calculations

Inactivation of acetylcholinesterase (AChE) due to inhibition by organophosphorus (OP) compounds is a major threat to human since AChE is a key enzyme in neurotransmission process. Oximes are used as potential reactivators of OP-inhibited AChE due to their α-effect nucleophilic reactivity. In search of more effective reactivating agents, model studies have shown that α-effect is not so important for dephosphylation reactions. We report the importance of α-effect of nucleophilic reactivity towards the reactivation of OP-inhibited AChE with hydroxylamine anion. We have demonstrated with DFT [B3LYP/6-311G(d,p)] calculations that the reactivation process of sarin–serine adduct 2 with hydroxylamine anion is more efficient than the other nucleophiles reported. The superiority of hydroxylamine anion to reactivate the sarin-inhibited AChE with sarin–serine adducts 3 and 4 compared to formoximate anion was observed in the presence and absence of hydrogen bonding interactions of Gly121 and Gly122. The calculated results show that the rates of reactivation process of adduct 4 with hydroxylamine anion are 261 and 223 times faster than the formoximate anion in the absence and presence of such hydrogen bonding interactions. The DFT calculated results shed light on the importance of the adjacent carbonyl group of Glu202 for the reactivation of sarin–serine adduct, in particular with formoximate anion. The reverse reactivation reaction between hydroxylamine anion and sarin–serine adduct was found to be higher in energy compared to the other nucleophiles, which suggests that this α-nucleophile can be a good antidote agent for the reactivation process.