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We argue for an account of chemical reactivities as chancy propensities, in accordance with the 'complex nexus of chance' defended by one of us in the past. Reactivities are typically quantified as proportions, and an expression such as "A + B → C" does not entail that under the right conditions some given amounts of A and B react to give the mass of C that theoretically corresponds to the stoichiometry of the reaction. Instead, what is produced is a fraction α < 1 of this theoretical amount, and the corresponding percentage is usually known as the yield, which expresses the relative preponderance of its reaction. This is then routinely tested in a laboratory against the observed actual yields for the different reactions. Thus, on our account, reactivities ambiguously refer to three quantities at once. They first refer to the underlying propensities effectively acting in the reaction mechanisms, which in 'chemical chemistry' (Schummer in Hyle 4:129–162, 1998) are commonly represented by means of Lewis structures. Besides, reactivities represent the probabilities that these propensities give rise to, for any amount of the reactants to combine as prescribed. This last notion is hence best understood as a single case chance and corresponds to a theoretical stoichiometric yield. Finally, reactivities represent the actual yields observed in experimental runs, which account for and provide the requisite evidence for/against both the mechanisms and single case chances ascribed. [ABSTRACT FROM AUTHOR]

This study investigates the crystal structure, physicochemical properties, and pharmacokinetic profile of Ethyl 2-amino-6-methyl-4,5,6,7-tetrahydrothieno[2,3-c]pyridine-3-carboxylate (EAMT) as a potential therapeutic agent. The crystal structure was analyzed using Hirshfeld surface analysis in conjunction with the quantum theory of atoms in molecules (QT-AIM). Non-covalent interactions were evaluated through reduced-density gradient reduction, revealing that the EAMT crystal is stabilized by hydrogen bonds between EAMT molecules in the crystal and between EAMT molecules and water molecules. The molecular electrostatic nature of interactions was examined using MESP, while global and local descriptors were calculated to assess the compound's reactivity. Molecular docking with the Adenosine A1 receptor was performed and validated through a 50 ns molecular dynamics simulation (MDS). Results suggest that EAMT influences protein structure, potentially stabilizing specific secondary structure elements. The compactness analysis showed a slightly more compact protein conformation and a marginally increased solvent exposure in the presence of the EAMT ligand, as indicated by Rg and SASA values. The total binding free energy (ΔG total) was determined to be −114.56 kcal/mol. ADMET predictions demonstrated EAMT's compliance with Lipinski's and Pfizer's rule of five, indicating good oral availability. The compound may exhibit low-potency endocrine activity. In conclusion, EAMT presents potential as a therapeutic candidate, warranting further exploration of its molecular interactions, pharmacokinetics, and potential safety concerns. [ABSTRACT FROM AUTHOR]

In this work, 2-thioxo -3 N-(2-ethoxyphenyl -5[4′-methyl -3′N-(2′-ethoxyphenyl) thiazol-2′(3′H)-ylidene] thiazolidin-4-one (E2Th2) was synthesized and its molecular structure determined by FT-IR, UV-Vis and NMR spectroscopic techniques along with a single crystal X-ray diffraction study. Quantum chemical calculations were performed to better understand its structural, spectroscopic and electronic properties such as HOMO and LUMO energy gap, MEP and global reactivity descriptors. Theoretical calculations were performed using density functional theory (DFT) based on the B3LYP/6-311G (d,p). Vibrational frequencies were assigned on the basis of PED and electronic transitions are calculated according to time-dependent density functional theory (TD-DFT). The HOMO and LUMO analysis are used to determine the charge transfer within the molecule. The NLO activity evaluation was based on the determination of the dipole moment, polarizability (α), first-order hyperpolarizability (β) and the second-order hyperpolarizability (γ) which were calculated using the same level of theory. The hyper-hardness descriptor (Γ) was explored and correlated with the NLO properties. Additionally, the stability of the molecule occurring from hyper-conjugative interaction, intramolecular hydrogen bond and charge delocalization were quantified using NBO analysis. The repulsive, attractive, and van der Waals strong and weak interactions were revealed by RDG and HS analyses. Finally, results have shown that the title compound can be used as attractive future NLO material. [ABSTRACT FROM AUTHOR]

Surface hydroxylation has been extensively studied over the years for a variety of applications, and studies involving hydroxylation of different silica surfaces are still carried out due to the interesting properties obtained from those modified surfaces. Although a number of theoretical studies have been employed to evaluate details on the hydroxylation phenomenon on silica (SiO2) surfaces, most of these studies are based on computationally expensive models commonly based on extended systems. In order to circumvent such an aspect, here we present a low-cost theoretical study on the SiO2 hydroxylation process aiming to evaluate aspects associated with water-SiO2 interaction. Details about local reactivity, chemical softness, and electrostatic potential were evaluated for SiO2 model substrates in the framework of the density functional theory (DFT) using a molecular approach. The obtained results from this new and promising approach were validated and complemented by fully atomistic reactive molecular dynamics (FARMD) simulations. Furthermore, the implemented approach proves to be a powerful tool that is not restricted to the study of hydroxylation, opening a promising route for low computational cost to analyze passivation and anchoring processes on a variety of oxide surfaces. [ABSTRACT FROM AUTHOR]

We review the early works which were precursors of the Conceptual Density Functional Theory. Starting from Thomas–Fermi approximation and from the exact formulation of Density Functional Theory by Hohenberg and Kohn's theorem, we will introduce electronegativity and the theory of hard and soft acids and bases. We will also present a general introduction to the Fukui functions, and their relation with nucleophilicity and electrophilicity, with an emphasis towards the importance of these concepts for chemical reactivity. [ABSTRACT FROM AUTHOR]

Effects of substituent groups on aqueous solubility, chemical reactivity and absorption wavelength of Disperse red 73 (DR73) were theoretically investigated using density functional theory (DFT) method. This study is in view of introducing new monoazo disperse dyes with improved aqueous solubility, absorption behaviour, and degradation tendency. Aqueous solubility was calculated using Cramer et al. solubility equation and the parameters used were obtained using conductor-like screening model for realistic solvation (COSMO-RS). Chemical reactivity and catalytic affinity were evaluated using some molecular orbital dependent reactivity descriptors. Susceptibility of the molecules to radical attacks was predicted using Fukui functions. Absorption wavelength was calculated using the B3LYP functional with the 6-31G* basis set. The results showed that electron withdrawing −CN substituent promoted aqueous solubility of DR73 more than the −NO2 counterpart, while the solubility is mostly enhanced by −NH2 substituent compared to the other electron donating groups studied. Most of the derivatives yielded longer absorption wavelength in the visible region and are chemically less stable (i.e. more degradable) compared to the parent molecule. Among the photocatalysts considered, ZnO is predicted as the most efficient candidate for degradation of the dyes. Predicted properties showed remarkable sensitivity to substitution positions in the parent molecule. [ABSTRACT FROM AUTHOR]

The chemistry of 3-acetyl-4-hydroxyquinolin-2(1H)-ones has attracted increased attention in both synthetic organic and medicinal chemistry, as numerous advancements in the use of this family of important compounds seems to be of considerable value. This account summarizes the results from the literature focusing on synthesis of 3-acetyl-4-hydroxyquinolin-2(1H)-ones as well as their reactions are also discussed. [ABSTRACT FROM AUTHOR]

Abstract American Trypanosomiasis is a disease caused by the protozoan parasite Trypanosoma cruzi agent. Nifurtimox and benznidazole are effective drugs in the acute phase; however, are toxic and have adverse effects. Nonetheless, the nitroheterocycles are good models to design other compounds with less side effects. Theoretical and experimental studies have been performed about the structure and mode action of these drugs and at present, no effective treatment of this disease has been established yet, and the parasitic infections increase each year. The aim of this work, was to analyze the substituent effects on the physicochemical properties and chemical reactivity of selected antiparasitic 5-nitrofurans, using quantum-chemical descriptors: acidity, proton affinities, SESE, potential ionization, hardness, electrophilicity, aromaticity, dipole moment and Fukui functions at the DFT-M06-2X level in aqueous solution. The acidity of the azomethine group increases with the presence of the electron-withdrawing groups. The electron-donating groups favor the basicity and the energy of stabilization in the active molecule (NFX). The atomic charges, the quantum chemical descriptors and Fukui function (f k +) showed that the main reactivity takes place on the Ar-NO 2. These results reinforce the importance of the nitro group in the redox processes of the 5-nitrofurans that are involved in the trypanocidal effect. Graphical abstract Image 1 Highlights • Electronic structure plays an important role on the molecular design. • The electron-attractor substituent groups favor the acidity and the chemical reactivity of 5-nitrofurans. • Chemical reactivity and the physicochemical features are crucial in the trypanocidal effect of 5-nitroheterocycles. [ABSTRACT FROM AUTHOR]

Three different DFT methods, B3LYP, M06-2X and M06, with PCM (polarized continuum model) solvent environment were performed to study the binding of Ca 2+ with different groups of superplasticizers. Small monomers contained one or two groups, respectively, called as phosphonate, phosphate, carboxylate, sulfonate, sulfate and alkoxide were selected as theoretical models. The stable binding conformations of Ca 2+ with monomers containing a single group optimized by the three DFT methods are similar and the binding strength follows the order, phosphonate ≈ phosphate > carboxylate > sulfonate ≈ sulfate > alkoxide ≈ water. The chemical reactivity and the electrophilic attack, not the natural atomic charges, of those monomers contribute significantly to the binding strength with Ca 2+ . The stable conformations of monomers containing two groups binding with Ca 2+ are complex and the structures of the complexes by the three DFT methods are different for the phosphonate and phosphate. However, the order of the binding energies of those monomers with calcium ions calculated by the three DFT method are consistent and also agree with that of the monomers containing a single group. The values of the binding energies are two times more than the binding energies of the monomers containing single group. [ABSTRACT FROM AUTHOR]

This review described the synthetic methods, chemical reactivity and biological applications of furan carboxamide compounds. Furan-carboxamides are reported to have important and variable biological properties. The aim of this review is to highlight the chemistry and biological importance of this class of bioactive compounds. The basic sections covers: structure studies, synthetic methods pathways, synthesis of different heterocycles, reactions and biological applications. The reactions mechanisms of the unexpected products are discussed. The present study covers all the published work on the furan-carboxamides until now. [ABSTRACT FROM AUTHOR]

The value of the molecular electrostatic potential minimum (Vmin) and its topographical features (position, as well as the eigenvalues and eigenvectors of the corresponding Hessian matrix) are recently proposed as the criteria for characterizing a lone pair (Kumar A. et al., J. Phys. Chem. 2014, A118, 526). This electrostatic characterization of lone pairs is examined for a large number of small molecules employing MP4/6‐311++G(d,p)//MP2/6‐311++G(d,p) theory. The eigenvector of the Hessian matrix corresponding to its largest eigenvalue (λmax), is found to be directed toward the lone pair‐bearing‐atom, with λmax showing a strong linear correlation with Vmin. Large magnitudes of Vmin and λmax indicate a charge‐dense lone pair. The topographical features of Vmin are seen to provide insights into the interactive behavior of the molecules with model electrophiles, viz. HF, CO2, and Li+. In all the complexes of HF and majority of the other complexes, the interaction energy (Eint) correlates well with the respective Vmin, value, but for some deviations occurring due to other competing secondary interactions. The electrostatic interactions are found to be highly directional in nature as the orientation of interacting atom correlates strongly to the position of lone pair. In summary, the present study on a large number of test molecules shows that electrostatics is able to probe lone pairs in molecules and offers a simple interpretation of chemical reactivity. © 2017 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

We perform a theoretical study on a set of carbon nanorings (CycloParaPhenylenes or CPP) envisioned as molecular templates for the selective synthesis of carbon nanotubes. The shape of these precursors, originating from bending n phenylene units in para position until forming the corresponding nanoring [ n ]CPP, may drive the growth of armchair single-walled nanotubes. This kinetic and thermodynamic study covers a set of molecules with different diameters, analyzing the exothermicity and the reaction path of a CPP-based radicaloid mechanism. The methodology employed is based on validated density functionals for mechanistic studies, shedding light on the viability of this synthetic pathway. [ABSTRACT FROM AUTHOR]

The synthesis and application of ethyl 5-aminothieno[2,3-c]pyridazine-6-carboxylates as building blocks for the synthesis of polyfunctionalized heterocyclic compounds are reviewed. [ABSTRACT FROM AUTHOR]

A series of novel Quinazolinone derivatives were synthesized and characterized by various spectroscopic techniques. The nature of reactants and products of chemical reactions has been determined using thermodynamic parameters (H, G, S). The TD–DFT calculation of the compound shows that electronic excitations is n→π ∗ in nature and compounds having intramolecular hydrogen bonding is obvious in 1 H NMR, 13 C NMR, FT–IR measurements and ESP map. In 1 H NMR signal of the indolic NH protons appears at 7.26 ppm shows that intramolecular hydrogen is present in compounds. The vibrational analysis designates the presence of intramolecular hydrogen bonding N12 H34⋯O21 shows in lowering of NH and CO stretching vibrations frequency. The local reactivity descriptors Fukui functions (f k + , f k – ), local softness's (s k + , s k – ) and electrophilicity indices (ω k + , ω k – ) determine the reactive sites within molecule. The computed first hyperpolarizability (β 0 ) found to be 10.2254 × 10 − 30 e s u indicating that the compound is non–linear optical (NLO) material. [ABSTRACT FROM AUTHOR]

First-principles method has been employed to investigate the stability and local reactivity of Au-Pd nanoparticles. AucorePdshellnanoclusters are generally more stable than PdcoreAushellcounterparts for studied nanoparticles (55, 85, 147-atom). The stability of Au-Pd nanocluster is attributed to the strong charge transfers from Pd to Au atoms. The d-band centre and Fukui function values indicate that the low-coordination atoms possess the higher reactivity relative to other atoms. The two descriptors are generally in good agreement. [ABSTRACT FROM AUTHOR]

The present study emphasizes on structural, opto-electronic, vibrational, and nonlinear properties, at the electronic structure level, on the 4-fluoro-4-hydoxybenzophenone molecule using the first principles calculation. Detailed vibrational assignments of the wavenumbers are carried out on the basis of potential energy distribution and a good agreement between the reported and calculated wavenumbers has been observed. Furthermore, the molecular electrostatic potential surface predicts the reactive site of the molecule. From the time dependent density functional theory analysis of UV-visible spectra, a red shift has been observed at the maximum absorption wavelength when the gaseous medium is replaced by a solvent medium. The 4-fluoro-4-hydroxybenzophenone molecule possesses large hyperpolarizability value which implies its usefulness in nonlinear optical applications. [ABSTRACT FROM PUBLISHER]

The prediction of reactivity is one of the long-standing objectives of chemistry, contributing to enforce the link between theory and experiment. In particular, the regioselectivity of aromatic molecules has motivated the proposal of different reactivity descriptors based on foundational theories, like Frontier Molecular Orbital (FMO) theory and density functional theory, to predict and rationalize such regioselectivity. This article examines cases where reactivity descriptors, based on FMO theories, are known to have failed, specifically on electrophilic aromatic substitution reactions, through a simple but effective new reactivity model: the Orbital-weighted Fukui function ( [ABSTRACT FROM AUTHOR]

Two kaolins from different geological areas of South Africa were compared as precursors for the synthesis of ZSM-5. Their effects on the formation of ZSM-5 and its physicochemical properties were investigated. The mineralogical phases, morphology, surface area and porosity characteristics, acidity and chemical nature of the synthesised materials were investigated using XRF, XRD, HRSEM-EDS, N 2 physisorption (BET) analyses, NH 3 -TPD and 27 Al/ 29 Si MAS NMR. The two kaolins differed in structural order and XRD showed Fishoek (SK) kaolin to be more crystalline than the Grahamstown (BK) kaolin with Stoch indices of 0.97 and 1.17 respectively. The more disordered BK resulted in a faster crystallisation of ZSM-5. ZSM-5 derived from the two kaolins showed a remarkable difference in its physicochemical properties as well. N 2 physisorption confirmed a well-developed microporous structure manifested from the slower crystallisation kinetics of SK. The slower dissolution of reactants in the gel also resulted in a difference in the chemical properties as a highly acidic ZSM-5 was derived from SK (1313 μmol) as compared to BK (633 μmol). 27 Al MAS NMR studies clearly confirmed the presence of highly reactive Al species in the synthesis gel of BK derived ZSM-5 correlating the enhanced crystallisation kinetics observed with the kaolin structural order and chemical reactivity. [ABSTRACT FROM AUTHOR]

Inflammatory response events are initiated by a complex series of molecular reactions that generate chemical intermediaries. The structure and properties of peptides and proteins are determined by the charge distribution of their side chains, which play an essential role in its electronic structure and physicochemical properties, hence on its biological functionality. The aim of this study was to analyze the effect of changing one central amino acid, such as substituting asparagine for aspartic acid, from Cys–Asn–Ser in aqueous solution, by assessing the conformational stability, physicochemical properties, chemical reactivity and their relationship with anti-inflammatory activity; employing quantum-chemical descriptors at the M06-2X/6-311+G(d,p) level. Our results suggest that asparagine plays a more critical role than aspartic acid in the structural stability, physicochemical features, and chemical reactivity of these tripeptides. Substituent groups in the side chain cause significant changes on the conformational stability and chemical reactivity, and consequently on their anti-inflammatory activity. [ABSTRACT FROM AUTHOR]

Pinocembrin flavonoid (C 15 H 12 O 4 ), 5,7-Dihidroxyflavanone, is one of the major chemical constituents of propolis extracts which is characterized by possessing antioxidant activity. However, the relationship between its structure and antioxidant properties are little known. The principal objective of this work was to study the molecular structure and chemical reactivity (electronic affinity, A ; ionization potential, I ; electronegativity, χ ; hardness, η ; electrophilicity, ω ; Fukui indices) of pinocembrin employing the Density Functional Theory (DFT) method and different model chemistries, which include the PBEPBE, PBE1PBE, MPW1PW91, B3LYP and M05-2X functionals in combination with the 6-31G(d,p) and 6-31+G(d,p) basis set, in search of the most accurate results. This study indicate that different model chemistries were able to reproduce the molecular structure of pinocembrin compared with experimental reference data ( R > 0.99). It is remarkable that M05-2X/6-31G(d,p) afford the best quality to simulate pinocembrin structure. Low values of chemical potential, obtained by different model chemistries, indicate that pinocembrin is capable to donate electrons and participle as an antioxidant compound, while the local reactivity analyzed through the Fukui indices showed that C (4) was the preferred sites for nucleophilic attack, and O (4) and C (8) sites participle in electrophilic and radical attack. [ABSTRACT FROM AUTHOR]

The history of technology provides many cases where simplified forms of man-made motion replace tangled forms of native motion. One of the reasons for these substitutions is the lack of approaches to the categorical recognition of information about the topology and the geometry of body in the state of transformation. As a consequence, there arises a barrier between chemistry and materials science. The aim of this paper is to direct a way to the solution of the problem, using a simple example of chemical bursting with the dimension of becoming D = log 2/log 2 = 1 for the one-dimensional process and D = log 7/log 2 ≈ 2.8074 for the three-dimensional process at all their scales. [ABSTRACT FROM AUTHOR]

We here formulate and implement linear response function (LRF) of the Mayer bond order (MBO), which is expected to be a new indicator to describe intrinsic chemical reactivity of molecules. We calculate LRFs of the MBOs of para-substituted benzoic acids, and compare the results with the Hammett substituent constants and computational results of acid dissociation constants that were previously reported. The results are discussed from the viewpoint of the applicability of LRF of the MBO to estimate the relative reactivity of the substituted benzoic acids. [ABSTRACT FROM AUTHOR]

Three synthesized coumarin derivatives were studied for their quantumchemical properties. These compounds are commonly used as starting material for many syntheses of biologicaly active compounds. In order to explore the theoreticalexperimental consistency, DFT global chemical reactivity descriptors (chemical hardness, total energy, electronic chemical potential and electrophilicity) were calculated for these compounds using standard Spartan 10 software. Complete geometry optimization was carried out by B3LYP/6-31G* level of theory. Some quantumchemical calculations correlated well with experimental work; mechanisms of reactions with these compounds as starting material were partially explained by these calculated parameters. These calculations were once more proof that by means of mathematical models it is possible to describe chemical interactions and simulate the behavior of chemical systems - molecules and reactions. [ABSTRACT FROM AUTHOR]

Imatinib, a phenylaminopyrimidine compound is a therapeutic drug for treatment of chronic myelogeneous leukaemia and gastrointestinal stromal tumours. It is well known that imatinib mesylate (ImM) exists in two polymorphic forms α and β. In this work, a computational study on molecular properties of ImM polymorphs is presented using density functional theory, B3LYP functional and 6-311G(d,p) as basis set. Natural bond orbital analysis is carried out to investigate the various conjugative and hyperconjugative interactions within the molecule and their second-order stabilisation energy (E(2)). The local nucleophilic reactivity descriptors such as Fukui functions (), local softness () and electrophilicity indices () analyses are carried out to determine the reactive sites within the molecule. To determine strength and nature of intra- and intermolecular interactions, topological parameters as electron density (ED) (ρBCP), Laplacian of ED (▽2ρBCP) and total electron energy density (HBCP) at bond critical points have been analysed by ‘quantum theory of atoms in molecules’ in detail. The computed first hyperpolarisability (β0) for both forms of ImM molecule (10.927 and 10.354 × 10− 30 esu) suggests that the investigated molecule is an attractive object in future for non-linear optical properties. Molecular electrostatic potential surface of ImM has been mapped to predict the inhibitory activity and binding affinity with a panel of protein tyrosine kinases. [ABSTRACT FROM AUTHOR]

In this paper, we report the chemical reactivity between Ce0.7RE0.2Mo0.1O2 (RE=Y, Sm) (CRMO) and 8mol% yttria-stabilized zirconia (8YSZ), at an elevated temperature in air and investigate the crystal structure, morphology, and electrical conductivity of their reaction product. Solid state reaction between CRMO and 8YSZ starts to occur on heating at 1000°C and yields single phase Mo-doped fluorite solid solution at 1200°C, as confirmed by powder X-ray diffraction (PXRD). Thermo-gravimetric analysis in 5% H2/N2 showed that weight loss in the case of solid solution is less compared to pure CRMO. In order to study the ability of CRMO to be co-fired with YSZ, compatibility tests between CRMO and 8YSZ in the pellet form were also performed. It was found that electrical conductivity data of CRMO-YSZ solid solution (CRZMO) in the air and wet H2 was lower than CRMO, due to the formation of defect associates and decrease in concentration of charge carriers. [ABSTRACT FROM AUTHOR]

This study shows that the chemical reactivities depend on the orbital energy gaps contributing to the reactions. In the process where a reaction only makes progress through charge transfer with the minimal structural transformation of the reactant, the orbital energy gap gradient (OEGG) between the electron-donating and electron-accepting orbitals is proven to be very low. Using this relation, a normalized reaction diagram is constructed by plotting the normalized orbital energy gap with respect to the normalized intrinsic reaction coordinate. Application of this reaction diagram to 43 fundamental reactions showed that the majority of the forward reactions provide small OEGGs in the initial stages, and therefore, the initial processes of the forward reactions are supposed to proceed only through charge transfer. Conversely, more than 60% of the backward reactions are found to give large OEGGs implying very slow reactions associated with considerable structural transformations. Focusing on the anti-activation-energy reactions, in which the forward reactions have higher barriers than those of the backward ones, most of these reactions are shown to give large OEGGs for the backward reactions. It is also found that the reactions providing large OEGGs in the forward directions inconsistent with the reaction rate constants are classified into S N2, symmetric, and methyl radical reactions. Interestingly, several large-OEGG reactions are experimentally established to get around the optimum pathways. This indicates that the reactions can take significantly different pathways from the optimum ones provided no charge transfer proceeds spontaneously without the structural transformations of the reactants. © 2014 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Highlights: [•] Molecular precursor reactivity dictates the rate of nucleation of different nanocrystalline phases. [•] Suppressing homogeneous nucleation enables the growth of nonblinking ‘giant’ nanocrystals. [•] Metal deposition stabilizes and activates semiconductors in photocatalytic deoxygenation. [•] Surface ligand doping and organization controls nanocrystal activity and interfacial properties. [Copyright &y& Elsevier]

In this paper the theoretical reactivity of three dyes commonly used in textile industry was studied: indigo (1) from indolic family, yellow disperse 3 (2) from azoic family and disperse blue 3 (3) from antraquinonic family. The computational calculations were carried out with the Spartan-Pro Program for performing conformational analysis. Then, the optimization of the more stable conformers at B3LYP/6-31G(d) level theory with Gaussian 09 program was performed. The chemical reactivity was orientated to the calculation of electronic properties through of Mulliken charges and electrostatic potential surfaces, finding that disperse blue 3 has more reactive sites than the other dyes, being therefore more susceptible to nucleophilic and electrophilic attack. [ABSTRACT FROM AUTHOR]

Prediction of chemical reactivity has become one of the highest priority tasks of computational chemistry since the development of the methods of modeling electronic structure. Despite the general simplicity of the physical concept of reactivity and the rapid development of modern density functional theory (DFT) methods, this task remains state-of-the-art for systems with wavefunctions that have a multiconfigurational character. In such cases, for the accurate description of reactivity one needs to use multiconfigurational approaches that are much heavier computationally then ordinary single-determinant DFT methods. Moreover, the complexity of the calculation of reactivity is increased by the necessity to calculate ionic and transition states. These computational challenges can be addressed by employing the concepts of Koopmans' theorem and its extension to a multiconfigurational case. We present a simplified methodology for the calculation of Fukui functions, based on Koopmans' approximation for multiconfigurational Green's functions developed in our previous works. Also, an extension of this methodology based on perturbation theory has been developed to improve accuracy. [ABSTRACT FROM AUTHOR]

The prediction of the series of [AuXM] compounds (with X = H, F, Cl, Br, I and M = Li, Na, K, Rb, Cs) has been carried out by ab initio and DFT calculations. The systems are chemically stable due to their high chemical hardness. An unusual Au-Au attraction was found on each of the compounds along the series, addressing a strong metalophilic interaction of the aurophilic type. A strong aromatic character on the center of the [AuX] ring was also detected in the compounds under study, enhancing the stability of the species. The mechanism behind the bonding of the systems is mainly ruled by an electrostatic interaction among the 2 M cations and the [AuX] monolayer sheet in accordance with CDA and Ziegler analysis; only a slight orbital contribution yielded by back-donation from the alkaline metals to the [AuX] monolayer sheet is involved. It was shown that the [AuClM] group has the highest Fukui indexes, indicating that a catalytic reaction may rise from an electrophilic attack centered at the Au atoms or a nucleophilic attack on the alkaline-earth metals. The latter was tested with the most stable system of this group, namely [AuClLi], allowing it to interact with a CO molecule; the optimized [AuClLi] [CO] system represents a bound state that highlights the reactive properties of the species. An extended ...-M-S-M-S-M-... (with S representing the [AuX] system) linear chain model was also predicted at DFT level. Considering its spatial representation of the frontier molecular orbitals, it was found that a possible electronic transfer along the chain may take place via the triggering of an electron, suggesting the existence of a nanowire. [ABSTRACT FROM AUTHOR]

The structure and chemical reactivity of some derivatives of the anticancer drug cisplatin coordinated with bioactive ligands was investigated at mPW1PW/LANL2DZ level theory in the conceptual density functional theory. Global descriptors allowed analyzing the reactive nature of these complexes. The stability of the complexes increases in aqueous phase. Calculated geometries of the complexes cisplatin, carboplatín and cis-dichloro[(L,D)-Ornithine]platinum(II) are in agreement with their available X-ray data. The electrophilicity index calculated for the complexes were higher than those predicted for cisplatin, implying that the binding of these ligands favors the reactivity of these complexes [ABSTRACT FROM AUTHOR]

Abstract: The M06 family of density functionals has been assessed for the calculation of the molecular structure and properties of the Rhodamine B molecule. The chemical reactivity descriptors have been calculated through Conceptual DFT. The active sites for nucleophilic and electrophilic attacks have been chosen by relating them to the Fukui function indices and the dual descriptor f (2)(r). A comparison between the descriptors calculated through vertical energy values and those arising from the Koopmans’ theorem approximation have been performed in order to check for the validity of the last procedure. [Copyright &y& Elsevier]

This review describes the preparation and chemical reactivity of 2-chromanols. These derivatives appear as interesting intermediates in the synthesis of various natural products and biologically active compounds. [ABSTRACT FROM AUTHOR]

In this work, we studied a copper complex-based dye, which is proposed for potential photovoltaic applications and is named Cu (I) biquinoline dye. Results of electron affinities and ionization potentials have been used for the correlation between different levels of calculation used in this study, which are based on The Density Functional Theory (DFT) and time-dependent (TD) DFT. Further, the maximum absorption wavelengths of our theoretical calculations were compared with the experimental data. It was found that the M06/LANL2DZ + DZVP level of calculation provides the best approximation. This level of calculation was used to find the optimized molecular structure and to predict the main molecular vibrations, the molecular orbitals energies, dipole moment, isotropic polarizability and the chemical reactivity parameters that arise from Conceptual DFT. [ABSTRACT FROM AUTHOR]

The ability of substituted boranes, X nBH3− n, to form stable complexes with the hydrogen molecule is analyzed by making use of computational chemistry and local reactivity parameters. In these complexes, the hydrogen molecule acts as a Lewis base while the borane moiety is the Lewis acid. Electronegative groups (X = CF3, F, OH) are selected to increase the acidity of the borane and it is found that the energetic stability of the complexes is only increased for the trifluoromethyl-substituted Lewis acids, at the MP2/6-311++g(3df, 3pd) level. It is also found that the BLYP density functional underestimates the adduct stability of these species. On the other hand, fluoroboranes and hydroxyboranes do not form donor-acceptor adducts with the hydrogen molecule; instead, we find weakly bounded van der Waals complexes. Additional features on the intrinsic reactivity of boranes are analyzed with the molecular electrostatic potential and the acceptor Fukui function. The nature of the interaction among the boranes and the hydrogen molecule is explored by using the topological analysis of the electron density through the Bader's Atoms-in-Molecules theory. © 2012 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

The structures, energetics, as well as several important chemical parameters, of antiretroviral drugs - nucleoside reverse transcriptase inhibitors (NRTIs) - and natural deoxyribonucleosides in both neutral, and positively and negatively charged states, are investigated. These studies are carried out within the frame work of first-principles density-functional theory (DFT), using the Becke-Lee-Yang-Parr (BLYP) generalized gradient corrections to the local spin density approximation exchange and correlation energy, norm-conserving pseudopotentials and a plane-wave expansion of Kohn-Sham orbitals. Conceptual DFT is used to determine global and local chemical reactivity parameters. Our results are in good agreement with the best available experiments to date. The variation in the bond lengths and bond angles on cation formation indicates that the electron is lost from the base part of these molecules. Further, the presence of the deoxyribose sugar moiety lowers their ionization potential and increases their electron affinity, in comparison to the isolated DNA base. The effectiveness of the drug action in terminating the viral DNA chain, is explained using the global reactivity parameters, by comparing the reactivities of the drug molecules with those of the competing deoxyribonucleosides. The widely followed clinical practice, of avoiding the simultaneous administration of certain drugs, is also explained from the hardness and softness parameters. For most of the drug molecules, our study validates the generally accepted wisdom, that monophosphorylation is the crucial reaction step in the phosphorylation reaction in DNA nucleotide synthesis. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Chemical reactivity descriptors are derived within the framework of the pair density functional theory. These indices provide valuable information about bonding rearrangements and activating mechanisms upon electrophilic or nucleophilic reactions. Indices derived and tested in this work represent nonlocal counterparts of the local reactivity indices derived in the context of conceptual density functional theory (CDFT) and frequently used in reactivity studies; the Fukui function, the local softness and the dual descriptor. In this work, we show how these nonlocal indices provide a quantum chemical basis to explain the success of qualitative resonance models in chemical reactivity predictions. Also, local information is implicitly contained as CDFT indices are obtained by simple integration. As illustrative examples, we have considered in this work the Markovnikov's rule, the reactivity of enolate anion, the nucleophilic conjugate addition to α,β-unsaturated compounds and the electrophilic aromatic substitution of benzene derivatives. The densities used in this work were obtained with Hartree-Fock, Kohn-Sham DFT, and singles and doubles configuration interaction (CISD) approaches. © 2012 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Abstract: We have reported the dependence of projectile mass, chemical reactivity and effect of molecular beams on ion induced nano structure formation, when 8keV He1+, N1+, O1+, Ar1+ atomic ions and 16keV and molecular ions are used to bombard a Si(100) surface at an incidence angle of 60°. It is shown that the initiation and growth of ripple structures depend not only on the collision cascades but also on the chemical reactivity and molecular state of the projectiles. This experimental investigation explores the necessary requirements for ion induced controlled nanopatterning. [Copyright &y& Elsevier]

The reactive behavior of GABA and its agonist molecules have been investigated using B3LYP hybrid density functional method at the 6-311++G** basis set level, in the gas phase and dielectric media. The calculations have been performed to obtain optimized geometries, relative energies, net atomic charges, HOMO, and LUMO energies. Solvent effects have been analyzed using isodensity polarized continuum model (IPCM) for four different solvents, which are chloroform, ethanol, DMSO, and H2O. The results have suggested that both the amino group and carboxyl group have been two of the most important active site for interactions between all compounds and their receptors. In addition they have suggested that the amino group reflects the difference in biological activity for each all molecules. The structures of these agonists have provided an essential foundation for subsequent structure-activity analysis of ligand binding at GABA receptors, neuronal uptake inhibitors and transporters. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011 [ABSTRACT FROM AUTHOR]

Abstract: Allergic diseases of the skin and respiratory tract resulting from exposure to low molecular weight chemicals remain important issues for consumer product development and occupational/environmental health. Widespread opportunities for exposure to chemical allergens require that there are available effective methods for hazard identification and risk assessment. In the search for new tools for hazard identification/characterization there has been interest in developing alternative methods that will reduce, refine or replace the need for animals. One approach that shows promise is based on the measurement of the peptide reactivity of chemicals; the potential to form stable associations with protein/peptide being a key requirement for the induction of sensitization. Recent investigations using these systems have focused primarily on skin sensitizing chemicals. However, there is interest in the possibility of exploiting these same experimental approaches to distinguish between different forms of chemical allergens – as individual materials are primarily associated with one or the other form of sensitization in humans. These investigations may also provide insight into why chemical sensitizers can differ in the form of allergic disease they will preferentially induce. These opportunities are surveyed here against a background of the immunobiology of allergic sensitization and current state-of-the-art approaches to measurement of peptide/protein reactivity. [Copyright &y& Elsevier]

Abstract: High-energy resolution fast X-ray photoelectron spectroscopy was used to study the thermal evolution of ethylene on Ir(111). Temperature programmed photoemission spectra of the C 1s and Ir 4f 7/2 core levels were measured in 400ms/spectrum while ramping the temperature from 170 to 1120K. The C 1s spectra display a large variety of components, assigned to different carbon containing species present on the surface at increasing temperature, namely ethylene, ethylidene, ethylidyne, ethynyl, adsorbed carbon and finally graphene. Components due to the C–H stretch vibration excitation are clearly resolved for C2H4, CHCH3 and C2H3. The C 1s spectra of the last two species display also shifted components that belong to non-equivalent carbon atoms. At temperatures higher than 900K the narrowing of C 1s spectra is caused by graphene formation. Also the Ir 4f 7/2 spectra are strongly affected by the presence of the different species. The clean surface component moves initially towards the bulk peak and shifts back and forth along the series, to recover the binding energy position corresponding to the clean surface when the graphene layer is completely formed. A comparison of ethylene interaction with Ir(111) and Pt(111) is presented. [Copyright &y& Elsevier]

Abstract: The area of fire protection has grown over the last decades with an increasing use of brominated flame retardants (BFRs). Some of the BFRs are phenolic compounds as applied, e.g. tetrabromobisphenol A and 2,4,6-tribromophenol. Others, like the polybrominated diphenyl ethers (PBDEs), can be metabolized to phenolic compounds, i.e. polybrominated phenoxyphenols (OH-PBDEs). OH-PBDEs, have to our knowledge never been commercially produced, but some are well known natural products, and found in high concentrations in biota. The present study is aimed to determine the susceptibility of OH-PBDEs to undergo photolysis when dissolved in water and to compare their reactivity with a couple of PBDE congeners. A previously developed method for studies of photolysis was applied and adapted to include OH-PBDEs in water at pH 7 and 11, water/methanol and water/hydrogen peroxide. The results indicate a change in reaction rates for the photolysis of OH-PBDE in different aqueous media and pH dependence. The results from the present study show that hydroxylated compounds rapidly undergo photolytic transformations in water. The OH-PBDEs are more rapidly transformed then PBDE congeners with similar numbers of bromine substituents. All the OH-PBDEs, independent of structure, are rapidly transformed, with approx. the same rate, when hydrogen peroxide is present, indicating another route of reaction. Polybrominated dibenzo-p-dioxins (PBDDs) are indicated as transformation products upon photolysis of OH-PBDEs with a favorable bromine substitution pattern. [Copyright &y& Elsevier]

Abstract: Wool powders with various particle sizes have been produced using different milling techniques. Scanning electron microscopy (SEM) showed gradual breakdown of the fibre as it was progressively converted into powder form. Chlorination enhanced the effectiveness of subsequent air-jet milling. X-ray photoelectron spectroscopy (XPS) revealed an increase in the surface concentrations of oxygen and nitrogen, and a decrease in carbon and sulphur on conversion of the fibres into powders, as the cortex became exposed on the powder surface. An increased surface concentration of cysteic acid was observed for the chlorinated powder. Rapid uptake of dye by wool powders was observed in situations where there was virtually no uptake by the original fibre. Hydrophobic dyes were more readily sorbed than were hydrophilic dyes. The chlorination treatment led to a decrease in the sorption of acid dyes. Confocal microscopy, used in conjunction with a fluorescent stain, showed that chemicals were able to penetrate wool particles, even at room temperature. The rate and extent of uptake of dye by the finer powders were comparable to that obtained with activated charcoal, even though the surface area of the charcoal was 100 times greater. [Copyright &y& Elsevier]

Molecular simulations are important to predict thermodynamic values for reactive chemicals especially when sufficient experimental data are not available. Methylcyclopentadiene (MCP) is an example of a highly reactive and hazardous compound in the chemical process industry. In this work, chemical reactivity of 2-methylcyclopentadiene, including isomerization, dimerization, and oxidation reactions, is investigated in detail by theoretical computational chemistry methods and empirical thermodynamic-energy correlation. On the basis of molecular simulations, an average value of −15.2kcal/mol for overall heat of dimerization and −45.6kcal/mol for overall heat of oxidation were obtained in gaseous phase at 298K and 1atm. These molecular simulation studies can provide guidance for the design of safer chemical processes, safer handling of MCP, and also provide useful information for an investigation of the T2 Laboratories explosion on December 19, 2007, in Florida. [Copyright &y& Elsevier]