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En este trabajo se estudió el mecanismo de activación de un complejo neutro tridentado -N, -O, -S de paladio el cual presentó actividad catalítica hacia la polimerización de etileno. Se realizó una exploración de la superficie de energía potencial del proceso de activación del complejo para entender el origen de su actividad, utilizando la Teoría de los funcionales de la densidad (DFT) y se propuso un posible mecanismo de activación identificando los intermediarios y estados de transición. Los resultados de estos cálculos mostraron que la ruptura del enlace S-Pd para dar paso al complejo activado bidentado, es fácilmente realizable a temperaturas moderadas, por lo que el ligante empleado tiene potencial como punto de partida para sintetizar catalizadores neutros para la polimerización de olefinas.

In this work, simultaneous global optimization of geometry and total spin of small iron clusters Fe

A series of 2-, 3- and 4-pyridylmethyl-coumarin esters ligands (1–3) and their η3-allyl palladium complexes (1-Pd – 3-Pd) have been designed, synthetized and characterized. NMR analysis of compounds 1-Pd – 3-Pd indicated the presence of the allyl fragment. The molecular structure of 2, 3 and 1-Pd was determined by X-ray crystallographic analysis. The molecular structure 1-Pd reveals that coumarin ligand (2) is coordinated to the palladium center via a monodentate fashion through the nitrogen atom of the pyridinyl fragment while the allyl group is binding via a η3 fashion in an overall square-planar geometry completed with a chloride atom. An investigation of intermolecular interactions in crystal packing via a Hirshfeld surfaces and fingerprint plots analyses showed a wide variety of intermolecular contacts such as H•••O and H•••N hydrogen bonding, π•••π stacking, C–H•••π and carbonyl (lone pair)•••π interactions that generated polymeric arrays.

The present study examines bonding patterns between copper Cun clusters (n = 3–20) and aromatic compounds (benzene, phenol, and benzaldehyde) using a density-functional theory (DFT) approach. Hirshfeld population, natural bond orbital (NBO), molecular orbitals, and quantum theory of atoms in molecules (QTAIM) analyses suggested the formation of two types of interactions Cu–arene and C–H···Cu, in the complexation of copper clusters by an aromatic compound.

Quality control in the pharmaceutical sector as in other areas of industry should ideally be developed from the design to avoid the emergence of problems in the future. Endless quality control tests do not always represent a solution. Quality is considered to be designed according to the needs and use of a product. This chapter briefly presents a description of the use of experiment designs in pharmaceutical analysis; for example, the factors involved in the drug delivery system are described, and the variables are measured to define the level of quality achieved according to the objectives. This chapter includes information on using factorial, fractional, composite central, Taguchi, Plackett-Burman, Box-Behnken, and mixture experimental designs.

This work describes the reactions of [(μ-H)M3(CO)9(CCSiMe3)] (M = Ru, Os) with phosphines L (L = PMe3, PMe2Ph, PMePh2, and PPh3) which produce zwitterionic compounds [(μ-H)M3(CO)9(HCCPR3)] where cleavage of the C Si and formation of C P bonds occurs. In the case of the ruthenium derivatives, CO substitution also occurs. Spectroscopic and structural characterization of the products is described. A theoretical analysis was carried out in order to understand the transformation pathway in the formation of the zwitterionic compounds.

Monoaza-dithia- (1a – 3a) and diaza-tetrathia- (1b and 3b) macrocycles with a pendant 2-pyridylmethyl fragment have been prepared by the reaction between 2-(aminomethyl)pyridine with dibromide-dithioether derivatives. Four of the macrocycles have been characterized by X-ray crystallography, revealing the formation of two 14- and 15-membered monoaza-dithiaethers, and two 26- and 30-membered diaza-tetrathiaether macrocycles featuring one or two exo-2-pyridylmethyl fragments, respectively. The monoaza-dithiaethers macrorings adopt a twisted conformation while the diaza-tetrathiaethers macrorings display a rectangular conformation. Intramolecular interactions of macrorings 2a, 3a, 1b and 3b were studied by non-covalent interaction analysis. It was found that smaller macrorings are less stable than larger ones due to larger strain energies and that intramolecular dispersive interactions and hydrogen bonding play an important role in the macrocycle conformation adopted.

The use of corrosion inhibitors is an important method to retard the process of metallic attack by corrosion. The construction of mathematical models from theoretical-computational and experimental data obtained for different molecules is one of the most attractive alternatives in the analysis of corrosion prevention, whose objective is to define those molecular characteristics that are common in high-performance corrosion inhibitors. This review includes data of corrosion inhibitors evaluated in different media, the most commonly studied molecular descriptors, and some examples of mathematical models generated by different researchers.

The structural and electronic properties were calculated for seventy organic compounds used as dye sensitizers in solar cells, applying the B3LYP exchange-correlation energy functional with the 6-311G∗∗ basis set. Moreover, the present study proposes two new quantitative structure-property relationship (QSPR) models that enable the prediction of the power conversion efficiency (PCE) and maximum absorption wavelength (λmax) of these systems, the two QSPR models were validated using the coefficient of determination (R2) of 0.62 for both models with the leave-one-out cross-validation correlation coefficient (Q2LOO) of 0.55 and 0.57, respectively. Furthermore, applicability domain analysis was conducted in order to identify the related compounds via the extrapolation of the model.

Since the high incidence of aflatoxin M1 (AFM1) in milk and dairy products poses a serious risk to human health, this work aimed to investigate the complex formation between bovine α-lactalbumin (α-La) and AFM1 using different spectroscopic methods coupled with molecular docking studies. Fluorescence spectroscopy measurements demonstrated the AFM1 addition considerably reduced the α-La fluorescence intensity through a static quenching mechanism. The results indicated on the endothermic character of the reaction, and the hydrophobic interaction played a major role in the binding between AFM1 and α-La. The binding site stoichiometric value (n = 1.32) and a binding constant of 2.12 × 103 M−1 were calculated according to the Stern-Volmer equation. The thermodynamic parameters ΔH, ΔS and ΔGb were determined at 93.58 kJ mol−1, 0.378 kJ mol−1 K−1 and -19.17 ± 0.96 kJ mol−1, respectively. In addition, far-UV circular dichroism studies revealed alterations in the α-La secondary structures when the α-La-AFM1 complex was formed. An increased content of the α-helix structures (from 35 to 40%) and the β-sheets (from 16 to 19%) were observed. Furthermore, protein-ligand docking modelling demonstrated AFM1 could bind to the hydrophobic regions of α-La protein. Overall, the gathered results confirmed the α-La-AFM1 complex formation.

Two organotin compounds [{D(C6H4CH2)2}SnBr2] displaying intramolecular transannular Sn–D interactions (D = O, 3a; S, 3b) were synthesized by oxidation of elemental tin with the corresponding dibromo compounds D(C6H4CH2Br)2. Both organotin compounds were physicochemically characterized by EI-MS and NMR techniques and by single crystal X-ray crystallographic studies at room temperature. The spectroscopic and diffraction data agreed with the presence of a Sn–D intramolecular interaction. DFT calculations at the B3LYP/DGDZVP level were carried out. The topological analysis indicated that bond critical points are present along the Sn–D direction, and the electron localization function graphs showed the presence of electron lone pairs of the D donor atoms directed to the Sn acceptor atom.

The interaction of twenty anisole, thioanisole and derivatives with gold clusters was studied theoretically by DFT using different basis-sets. The Aun (n = 2–11) clusters were geometrically optimized and electronically characterized through their charges, molecular orbitals and bond energies. The studies of the most stable clusters Au10 and Au11 with the organic molecules displayed Cring Au, Au S, Au O, and Au---H C interactions; these last ones are significant because they play a crucial role in catalysis. The most stable systems were the Au11/sulfur derivatives, according to the HSAB model. These results were confirmed with the electron density topological analysis.

The structure of four type bis-1,4-dihydropyridine molecules was completely optimized employing semiempirical (PM3), ab initio (HF/3-21G(d), B3LYP/6-31G(d) and B3LYP/6-311++G(d,p) methods. The B3LYP/6-311++G(d,p) theory level provided a flat boat conformation. The observed ring distortions were not found to be influenced to a great extent by the position of the substituent present in the 4-phenyl ring, the second dihydropyridine ring. The HOMO, LUMO, chemical hardness, global softness, chemical electrophilicity and molecular electrostatic potential values were also appropriately calculated. The electronic parameters allowed to establish the reactivity of the four bis-1,4-dihydropyridine molecules. Moreover, the interactions between these compounds with two models of the voltage-gated calcium channel receptor were evaluated in connection to the reported vasodilator activity of these compounds.

The ring opening transformation of three substituted 2-(2-pyridyl)benzothiazolines of general formula [(C 6 H 4 NCS)(C 5 H 4 N)R] (R = C 5 H 4 N, 1 ; R = C 6 H 5 , 2 ; R = H, 3 ) was studied by their reaction with metal chlorides of Ni(II), Pd(II), and Pt(II). In these reactions, the anionic tridentate Schiff bases { L n } − coordinated to metal ions were identified. Seven metallic complexes of type [M( L n )Cl] [M = Pd, n = 1, R = C 5 H 4 N, ( 1a ); n = 2, R = C 6 H 5 , ( 2a ); n = 3, R = H, ( 3a ). M = Pt, n = 1, R = C 5 H 4 N, ( 1b ); n = 2, R = C 6 H 5 , ( 2b ); n = 3, R = H, ( 3b ), and M = Ni, R = C 6 H 5 , ( 2c )] were characterized in solution by NMR and vibrational spectroscopy in solid state. Crystal structures of benzothiazolines 1 and 2 and complexes 1a – 3a , 1b ·DMSO, and 2c were analyzed by X-ray diffraction studies. In all cases, mononuclear complexes with a distorted square planar geometry were obtained. For compounds 1 – 3 , the predominance of the benzothiazoline (ring form) over the Schiff base (open form) as well as the formation of the [Pd( L n )Cl] (n = 1–3) complexes were studied by DFT calculations at the PBEPBE/(Def2-TZVP,SDD) level in gas phase.

A convenient approach for the absolute configuration assignment of secondary alcohols in the (8R,1′R,2′S,5′R)-15,25, (8S,1′R,2′S,5′R)-15,25, (8R,1′R)-21–24, and (8S,1′R)-21–24 ester series, and of primary amines in the (8R,1′R)-32–37 and (8S,1′R)-32–37 amide series, by means of 1H NMR and VCD spectroscopy, using 2-cyano-2-indolylpropanoic acid as a chiral derivatizing agent is presented. DFT calculations were carried out to demonstrate the anisotropic effect of the indole skeleton on the chiral alcohol or the amine fragment. Vibrational circular dichroism (VCD) measurements of the above series indicated a VCD bisignated couplet resulting from the interaction of the ester carbonyl group and the CN group. The absolute configuration assignments were further tested by X-ray diffraction analysis.

In this work, two oligophenyleneimines type pentamers with terminal aldehydes, designated as DAFCHO (4,4&prime, ((((((2,5-bis(octyloxy)-1,4-phenylene)bis(methanylylidene))bis(azanyl ylidene))bis(9H-fluorene-7,2-diyl))bis(azanylylidene))bis(methanylylidene))bis(2,5-bis(octyloxy) benzaldehyde)) and FDACHO (4,4&prime, ((((((2,5-bis(octyloxy)-1,4-phenylene)bis(methanylylidene))bis (azanylylidene))bis(4,1-phenylene))bis(azanylylidene))bis(methanylylidene))bis(2,5-bis(octyloxy) benzaldehyde)) were synthesized by mechanochemistry method using 2,5-bis(octyloxy) terephtal aldehyde and 2,7-diaminofluorene or 1,4-phenylenediamine. All compounds were spectroscopically characterized using 1H and 13C-NMR, FT-IR and mass spectrometry MALDITOF. The optical properties of the compounds were analyzed by UV-vis spectroscopy using different solvents. We observed that DAFCHO and FDACHO exhibit interesting photochromic properties when they are dissolved in chloroform and exposed to sunlight for 3, 5 and 10 min. The value of the energy band gap was calculated from the absorption spectra without irradiation Egap(optical). It was 2.50 eV for DAFCHO in chloroform solution, and it decreased to 2.34 eV when it is in films. For FDACHO, it was 2.41 eV in solution and 2.27 eV in film. HOMO (Highest Occupied Molecular Orbital), LUMO (Lowest Unoccupied Molecular Orbital) and Egap(electrochemical) values were obtained by electrochemical studies. The results indicate that the compounds can be considered as organic semiconductors since their values are 2.35 eV for DAFCHO and 2.06 eV for FDACHO. The structural and electronic properties of the compounds were corroborated with a DFT (Density Functional Theory) study.

The possible interactions between α-zein and Ca2+ in nixtamalization process were analyzed from a multidisciplinary approach, considering the effect of these interactions on the thermal properties of the nixtamalized flour. SDS-PAGE under reducing and non-reducing conditions did not reveal differences between patterns of zeins from nixtamalized and control samples. However, analysis from affinity capillary electrophoresis indicated an increment in protein volume when calcium is added to zein extracted from nixtamalized flour. In addition, the binding constant for the zein-calcium interaction was calculated indicating a higher affinity for calcium by zein from nixtamalized samples. Molecular dynamics simulations indicated that the interaction α-zein-Ca2+ through C-ter was more favorable than Glu48. However, in excess of Ca2+ ions, each site could bind one calcium atom at the same time, confirming that aggregation of α-zein through calcium bridges is possible, expanding the technological applications of this protein.

The corrosion inhibition of N,N′-bis(benzimidazole-2-yl-methyl)amine (L1) and N, N′-bis(benzimidazole-2-yl-methyl)hydroxyethylamine (L2) was analyzed by electrochemical and theoretical methods. The data show that ligands form an adsorption layer over an iron surface, obeying the Langmuir isotherm ( Δ G a d s ° of −32.96 kJ mol−1); the value are higher than −20 kJ mol−1 but less than −40 kJ mol−1, belonging to a conversion stage of physical adsorption to chemical adsorption or a comprehensive adsorption. This is consistent with fractal dimension of the electrode surface, estimated by an impedance depression angle of a semicircle that the surface is homogeneously covered by the formation of an inhibitor film. Furthermore, the electronic parameters of the ligands were analyzed by DFT, showing that L1 and L2 possesses corrosion inhibition properties that give up its p orbital electron density through its HOMO orbital to the metal LUMO to form an adsorption layer, and this has been proved theoretically by the interaction of ligands with Fe30. In addition, we have collected corrosion inhibition data for around 70 organic compounds reported in the literature, and the inhibition data plotted against different inhibitors, showing that amine ligands are good corrosion inhibitors.

Two tin compounds [Sn(nBu)2(Ln)], where L1 {O(C6H4-2-N C(H)C6H4-2′-O)2}2 − and L2 {O(C6H4-2-C(H) NC6H4-2′-O)2}2 − enclosing five electron donors in an [ON2O2] core, were synthesized and structurally characterized by infrared and NMR spectroscopy and by single crystal X-ray crystallographic studies at room temperature. The hepta-coordinate geometry around the Sn centers is achieved through the bonding of two monodentate n-butyl groups and the coordination of the pentadentate Ln ligands, where the [ON2O2] core is forming a pentagonal base. The two types of oxygen atoms displayed different bonding situations around the Sn atom. DFT calculations with Gaussian 09 using PBEPBE/6-31G**/SDD level were carried out for both compounds. The topological analysis indicated that bond critical points are present along the Sn Oether direction.

The corrosion inhibition efficiency of carbon steel was evaluated using fifteen molecules derivated from imidazole and benzimidazole in 1.0 M HCl. The inhibition efficiency varies from 15.6 to 89.4%, depending on the chemical and the electronic structure of the compounds. The structural properties of the molecules under study were determined by density functional theory. Experimental and theoretical parameters were used to construct a model to predict the inhibition observed. The proposed model shows that inhibition efficiency is related to the molecule volume, charge, electronegativity, and aromaticity. The model is successfully used to predict the corrosion behavior of two additional molecules.

New derivatives of chrysin containing 2-mercaptopyridine (2a–2e) or 5-(trifluoromethyl)-2-mercaptopyridine (3a–3e) moieties were prepared from the reaction between bromides (1a–1e) and 2-mercaptopyridine or 5-(trifluoromethyl)-2-mercaptopyridine, respectively. Their structures were elucidated by NMR, IR and elemental analysis. The molecular structure of compounds 1a, 1c–1e, 2b–2e and 3a was determined by single-crystal X-ray diffraction studies. All rings in these structures are nearly coplanar and they showed an intramolecular hydrogen bond between the phenolic hydroxyl H atom and the carbonyl O atom that forms a six membered ring. The crystal packing also showed a wide variety of intermolecular contacts such as C–H⋯A, π–π, C–H⋯π and lone pair⋯π interactions which were supported by quantum theory of atoms in molecules (QTAIM), Hirshfeld surface, and fingerprint plot analyses. Biological activity of all compounds was tested in growth assays of the nematode Caenorhabiditis elegans. Compounds 2e, 3b and 3c inhibited larval development.

The Ir(I) complexes [TpMe2Ir(η4-1,4-diene)] 2b and 2c react thermally with a variety of aromatic aldehydes, 3a–e, to generate the metallabicyclic compounds 4e–k and the Fischer-type carbenes 5a–b in moderate yields. These reactions are proposed to take place with the initial formation of η1-aldehyde adducts as key intermediates. The formation of the metallabicyclic compounds 4e–k involves a formal decarboxylation process at the exo-2-oxazolidinone diene and an ortho metallation of the aromatic ring. The generation of the Fischer-type carbenes 5a–b is the result of a series of metal-based rearranged intermediates with no decarboxylation observed. Treatment of the η4-diene complex 2b with a variety of Lewis bases induces a change in the binding mode of the diene ligand from η4:π2 to η2:σ2 to form the Ir(III) derivatives 6b–d of composition TpMe2Ir-(η4:π2-1,4-diene)(L) (L = CO, MeCN, and C5H5N). A study of reactions of complex 2b with either mono- or poly-deuterated aldehydes was performed to understand the mechanisms of such processes. The results of these studies were used to determine plausible formation mechanisms of the metallabicyclic compounds 4e–4k and Fischer-type carbenes 5a–b compound series. These mechanisms were corroborated by density functional theory (DFT) calculations of the free energy profiles.

A systematic study was conducted on the production of hydrogen from formic acid with a Pd4 cluster using density functional theory (DFT) with the B3LYP and the 6-31G** orbital basis set for the C, H and O atoms, while a LANL2DZ effective core potential was used for palladium atoms. The thermodynamic results obtained show a favorable reaction mechanism for producing hydrogen with energy barriers lower than 30 kcal/mol. Moreover, the nature of the bonds involved in all system were analyzed using the theory of atoms in molecules (AIM) identifying the non-covalent interactions in this type of system.

The corrosion inhibition by cinnamic, p-coumaric and caffeic acid on carbon steel in 1.0 M HCl and its synergistic combination with KI was investigated using electrochemical and quantum chemical methods. A synergistic effect was observed when 2 mM potassium iodide was added to 0.1 mM inhibitor, where the corrosion inhibition efficiency (IE%) increased from 70% to 80%. In addition, the participation of iodide in the Fe surface was investigated during the adsorption of corrosion inhibitors such as cinnamic, p-coumaric and caffeic acids on Fe(1 1 0). The formation of an iodide monolayer on the Fe(1 1 0) surface was studied by density functional theory (DFT) periodic slab calculations. The DFT results revealed that cinnamic, p-coumaric and caffeic acids were adsorbed effectively on the metal surface through aromatic rings and carboxylic acid groups, as the bond distances with the Fe surface were 2.09 A for Fe C and 1.97 A for Fe O. Low adsorption energies were obtained; −52.90, −44.29 and −33.39 kcal/mol for cinnamic, p-coumaric and caffeic acids, respectively. Additionally, the magnetic moment of the Fe plane was changed significantly if the aromatic carboxylic acid adsorbed onto the metal surface had coating strengths as follows: cinnamic > p-coumaric > caffeic. The present study therefore provides a mechanistic understanding of the role of iodide in the corrosion inhibition process.

A microemulsion electrokinetic chromatography method was developed for the simultaneous detection and quantification of ciprofloxacin, norfloxacin, sulfamethoxazole, tetracycline, and oxytetracycline in feedstuff samples. The BGE composition was optimized by applying a Taguchi parameter design and consisted of phosphate 30 mmol/L, Tween-80 0.01 mmol/L, and fullerene 3 μmol/L, and adjusted to pH 8.0; the addition of surfactant and fullerene modifies the mobility of the analytes improving their resolution. Theoretical studies showed π-π and van der Waals interactions between antibiotic molecules and fullerene used as a pseudostationary phase. Under optimal conditions, limits of detection ranged from 0.7 to 1.5 μg/g; the analytes were separated in less than 6 min. The methodology proposed is useful for controlling and monitoring antibiotic residues in feedstuff samples.

Producción Científica, Deep eutectic solvents prepared by mixing choline chloride with urea or thiourea (1:2 molar ratio) were employed to evaluate their effects on the formation of cadmium electrodeposits on a reactive electrode composed of carbon steel 1018. The corrosion protection of carbon steel corresponds to the use of cadmium as a sacrificial anode. Differences in DES affect the electrochemical and corrosion behavior of cadmium., Junta de Castilla y Leon (Project VA171U14)

The relationship between structure and corrosion inhibition of a series of 30 imidazol, benzimidazol, and pyridine derivatives has been established through the investigation of quantum descriptors calculated with PBE/6-311++G**. A quantitative structure-property relationship model was obtained by examination of these descriptors using a genetic functional approximation method based on a multiple linear regression analysis. Our results indicate that the efficiency of corrosion inhibitors is strongly associated with aromaticity, electron donor ability, and molecular volume descriptors. In order to calibrate and validate the proposed model, we performed electrochemical impedance spectroscopy (EIS) studies on imidazole, 2-methylimidazole, benzimidazole, 2-chloromethylbenzimidazole, pyridine, and 2-aminopyridine compounds. The experimental values for efficiency of corrosion inhibition are in good agreement with the estimated values obtained by our model, thus confirming that our approach represents a promising and suitable tool to predict the inhibition of corrosion attributes of nitrogen containing heterocyclic compounds. The adsorption behavior of imidazole or benzimidazole heterocyclic molecules on the Fe(110) surface was also studied to elucidate the inhibition mechanism; the aromaticity played an important role in the adsorbate-surface complex.

A formal synthesis of the natural product (−)-flustramine B (3) is described, together with an easy and reliable approach for the absolute configuration assignment of a series of (3R,14S)- and (3S,14S)-oxindolylacetylphenyloxazolidinones 4, 6, 13a–c, and amides (+)- and (−)-14 by evaluation of the vibrational circular dichroism bisignated couplet resulting from the interaction of the C2 and C9 carbonyl groups. The absolute configuration assignment was validated by 1H NMR spectra and X-ray diffraction, and therefore (−)-flustramine B 3 was established as (3aS,8aR)-3.

Phenyleneimine oligomers 4,4'-(((1E,1'E)-(((1E,1'E)-(1,4-phenylenebis-(azanylylidene))bis(methanylylidene))bis(2,5-bis(octyloxy)-4,1-phenylene))bis(methanylyl-idene))-bis(azanylylidene))dianiline (OIC1MS) and 7,7'-(((1E,1'E)-(((1E,1'E)-((9H-fluorene-2,7-diyl)bis(azanylylidene))bis(methanylylidene))bis(2,5-bis(octyloxy)-4,1phenylene))bis- (methanylylidene))bis(azanylylidene))bis(9H-fluoren-2-amine) (OIC2MS) were prepared by means of conventional and mechanochemical synthesis and characterized by FT-IR, 1H- and 13C-NMR techniques. The optical properties of the compounds were studied in solution by using UV-visible spectroscopy, and the optical effects were analyzed as a function of solvent. The results show that OIC2MS exhibits interesting photochromic properties. Furthermore, the structural and electronic properties of the compounds were analyzed by TD-DFT. It was found that the mechanosynthesis is an efficient method for the synthesis of both tetraimines.

The molecular structures of several related cis-[j2-SS-(L)MHal2] compounds 1, 1DMSO, 2, 2H2O, 3DMSO, 4 and 5 where L = HOCH2Ph-S-CH2-CH2-S-PhCH2OH, M = Pd or Pt, and Hal = Cl or Br or I, were analyzed by single crystal X-ray diffraction analyses. In all complexes, the presence of intramolecular C–HM (M = Pd or Pt) interactions with distance values of 2.687–2.914 Å was established. In solid state both syn- or anti-conformers exist; this suggests that one or two ortho-hydrogen atoms on the phenyl rings are close to the metal. Furthermore, the existence of these weak interactions induce a significant effect on the geometry adopted by the metal center. The crystal structures show a wide variety of intermolecular noncovalent bonding such as hydrogen bonds, MM contacts, p-p, C–Hp and Halp interactions. For all the complexes, the structural analysis performed by Density Functional Theory (DFT) is in good agreement with parametric data obtained from X-ray measurements. Topological analyses of the electron density function [q(r)], which have been performed according to Bader’s Atoms in Molecules theory, reveal bond critical points relating the metal atom with aromatic ortho-hydrogen atoms. Laplacian r2 q(r) and density q(r) values indicate formation of the weak anagostic C–HM interactions Consejo Nacional de Ciencia y Tecnología/[CB-2011-01-167873]/CONACYT/México Consejo Nacional de Ciencia y Tecnología/[RE-2009-01-117114]/CONACYT/México UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Básicas::Centro de Investigación en Electroquímica y Energía Química (CELEQ) UCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Química

The capacity of 2,6-bis[((2-pyridylmethyl)oxy)methyl)]pyridine (BPMMP) to inhibit the corrosion of mild carbon steel in HCl was analyzed. In a polarization study, both the cathodic and anodic currents were appreciably decreased in the presence of BPMMP, suggesting that this ligand is effective at inhibiting corrosion at the metal surface. This conclusion is consistent with the results of impedance analysis, where only one time constant corresponding to one depressed capacitive loop was detected, and the diameter of the impedance plot was directly related to the concentration of BPMMP. Furthermore, when recurrence analysis was performed, a decrease in regular noise was observed due to the change of Shannon entropy when the inhibitor was present in the corrosive medium, showing that a high degree of recurrence increases the entropy of the system. Electrochemical data on some pyridyl-based inhibitors were collected from the literature and used to plot (i) I corr (A/cm2) vs. inhibition efficiency (η%) and (ii) ΔG°ads vs. inhibition efficiency (ƞ%) in order to examine the general relationships between these parameters. Furthermore, the interactions of the ligand BPMMP with different iron clusters (Fe15, Fe30, Fe45, and Fe60) were analyzed theoretically using density functional theory (DFT). The structural and electronic properties of BPMMP and its protonated form BPMMPH+ were studied before and after the interactions of BPMMP with the iron clusters. The first protonation was found to occur at pyridine nitrogen atom N1, resulting in a Gibbs free energy ΔG of −10.2 kcal/mol, with an energy difference of 5.3 kcal/mol between the two possible protonated conformers.

Structural and electronic properties of a series of 25 phosphonate derivatives were analyzed applying density functional theory, with the exchange-correlation functional PBEPBE in combination with the 6-311++G** basis set for all atoms. The chemical reactivity of these derivatives has been interpreted using quantum descriptors such as frontier molecular orbitals (HOMO, LUMO), Hirshfeld charges, molecular electrostatic potential, and the dual descriptor [[Formula: see text]]. These descriptors are directly related to experimental median lethal dose ([Formula: see text], expressed as its decimal logarithm [[Formula: see text]([Formula: see text]] through a multiple linear regression equation. The proposed model predicts the toxicity of phosphonates in function of the volume (V), the load of the most electronegative atom of the molecule (q), and the eigenvalue of the molecular orbital HOMO ([Formula: see text]. The obtained values in the internal validation of the model are: [Formula: see text]%, [Formula: see text]%, [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text]%. The toxicity of nine phosphonate derivatives used as test molecules was adequately predicted by the model. The theoretical results indicate that the oxygen atom of the O=P group plays an important role in the interaction mechanism between the phosphonate and the acetylcholinesterase enzyme, inhibiting the removal of the proton of the ser-200 residue by the his-440 residue.

Producción Científica, Deep eutectic solvents prepared by mixture of choline chloride with urea, thiourea and ethylene glycol (1:2 molar ratio) were used to study the electrochemical behavior Zn(II) at carbon steel 1018 electrode. Zn deposits were immersed in a corrosive media (NaCl 3%wt). Composition of the solvent employed causes a difference in electrodeposition and corrosion behaviors, being diffusion coefficient value a critical parameter associated to these processes.

In this work, “first-principles” Born–Oppenheimer Molecular Dynamics (BOMD) simulations were carried out for the solvation of Gd 3+ with water to yield solvated [Gd (H 2 O) n ] 3+ ( n = 1–9) complexes, and the optimized structures were identified by frequency analysis. The second difference in energy ( Δ 2 E ) show that [Gd(H 2 O) 8 ] 3+ is more stable than the other complexes, exhibiting a peak associated with the first solvation shell. The second energy difference for [Gd(H 2 O) n –Pt m ] 3+ was also carried and it yields relative high stability for[Gd(H 2 O) 8 –Pt 5 ] 3+ . The interaction of [Gd(H 2 O) n ] 3+ ( n = 8–9) with Pt n ( n = 3–7) clusters shows that [Gd (H 2 O) 8 ] 3+ adsorbs strongly on the Pt cluster by activating the Pt–H bond (2.55 A).

Pincer-type compounds of general formula [{C5H3N(CH2S)2}SnRHal] [Hal = Cl, R = n-Bu (1), Ph (2); Hal = Br, R = n-Bu (3)] were prepared by the reaction of the dithiol ligand {C5H3N(CH2SH)2} with a suitable organotin reagent. The molecular structures of the compounds were established by single-crystal X-ray diffraction and exhibit trigonal bipyramidal geometry at the tin atom with degrees of tbp distortion ranging from 75 to 81°, being caused by a transannular N → Sn interaction. The behavior of all tin compounds in solution was investigated by NMR spectroscopy revealing that the N → Sn interaction in solution was present on the basis of the chemical shifts values. DFT calculations with Gaussian 09 using M06/DGDZVP were carried out for all compounds. The structural data of the total optimization agreed with the experimental results and the topological analysis indicated that bond critical points are present along the N → Sn direction.

This report illustrates a successful C–H···Hal synthon-directed strategy to promote supramolecular aggregation of molecular luminescent complexes 1–6 into two- or three-dimensional supramolecular architectures. The tin complexes were prepared from the reaction of RnSnHal4–n compounds (R = n-Bu, Ph; Hal = Cl, Br; n = 0, 1) with (C5H4N)HC═N(C6H4)EH Schiff bases by either step-by-step synthesis [E = O (PyNO)] or multicomponent reaction [E = S (PyNS)]. Compounds 1–6 were characterized by IR, Raman, and 1H, 13C, and 119Sn NMR spectroscopic studies as well as by X-ray diffraction studies. In addition, the fluorescent properties of all compounds were also investigated in the solid state and in THF solutions; the emission wavelengths ranged from orange to red (λmax = 591–626 nm). Detailed structural characterization of the supramolecular organization of ordered solids revealed overall 2D and 3D interlinked networks driven by extensive C–H···Hal–Sn (Hal = Cl, Br) weak hydrogen bonds as primordial synthon and furth...

In this work, we report the conventional and mechanochemical synthesis of the a-diimine derivate of 2, 3-butanedione and the primary amine 2-aminoethanethiol designated DD-DC and DD-DC/MS respectively. The products were characterized by 1H and 13C-NMR, FT-IR, MS-EI and elemental analysis. The products were also electrochemically evaluated by potentiodynamic polarization technique in order to measure their corrosion inhibition efficiency on AISI 1018 steel, immersed in a corrosive solution type NACE TM 0177. The results indicate that the compound obtained under mechanosyntesis conditions, DD-DC/MS, presents better inhibitory properties with 53% efficiency at 10 ppm concentration. On the other hand, the compound obtained by conventional synthesis (DD-DC) presented efficiency of 29% at 10 ppm concentration. Also, the DFT results show that a-diimine derivatives possesses corrosion inhibition properties, consisting of the transfer of high-charge density which in the delocalization region (N=C–C=N) is formed by p (C=N) and SH, these moiety play an important role, because their electron lone pairs help to form a protective coating to form an adsorption layer. The results showed that cysteamine compound turns out to be a good corrosion inhibitor for the steel iron surface in an acid medium forming an adsorption film over metallic surface.