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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.

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 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.

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 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.

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, 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.

Chemical degradation of orlistat, (ORT) after melting and reaction of decomposition byproducts with sibutramine, SIB was studied. Interactions between the active pharmaceutical ingredients by using thermal analysis, TA, methods and other experimental techniques such as PXRD, IR and UV–vis spectroscopies were carried out to investigate chemical reactions between components. It was found that orlistat melts with decomposition and byproducts quickly affect sibutramine molecule and then reacting also with carnitine, CRN when the three active pharmaceutical ingredients (API’s) are mixed. However ORT byproducts do not react when ORT is mixed only with carnitine. It was found that compounds containing chlorine atoms react easily with orlistat when the temperature increases up to its melting point. Some reaction mechanisms of orlistat decomposition are proposed, the fragments in the mechanisms were found in the corresponding mass spectra. Results obtained indicate that special studies should be carried out in the formulation stage before the final composition of a poly-pill could be established. Similar results are commonly found for compounds very prone to react in presence of water, light and/or temperature. In order to explain the reactivity of orlistat with sibutramine and carnitine, theoretical calculations were carried out and the results are in agreement with the experimental results.

The symmetric ligands [Ar-S-CH2-Ph-S-(CH2)-]2, L1 (Ar = o-FPh) and L2 (Ar = p-FPh), and their PdII complexes (1 and 2) were synthesized and structurally characterized. Molecular structures of complexes 1 and 2 display the L1 and L2 ligands coordinating palladium in a κ2-SS bidentate fashion. The metal center exhibits a square planar geometry involving the two sulfur atoms and two chloride atoms which are oriented in cis disposition. Interestingly, the two ortho-hydrogen atoms from the phenyl rings in both complexes are engaged in Pd⋯Hortho interactions with distances from 2.976 to 3.280 A. These distances can suffer an increase or decrease in their longitude due to the presence of intramolecular C–H⋯π interactions. Additionally, the presence of Pd⋯H interactions in palladium complexes (1 and 2) were identified by an NCI analysis. The complexes 1, 2 and a similar complex 3 that also displays Pd⋯Hortho interactions have been evaluated in the Suzuki-Miyaura cross-coupling reactions.

The interactions of L-aminoglucosidic stereoisomers such as rhodostreptomycins A (Rho A) and B (Rho B) with cations (Mg2+, Ca2+, and H+) were studied by a quantum mechanical method that utilized DFT with B3LYP/6-311G**. Docking studies were also carried out in order to explore the surface recognition properties of L-aminoglucoside with respect to Mg2+ and Ca2+ ions under solvated and nonsolvated conditions. Although both of the stereoisomers possess similar physicochemical/antibiotic properties against Helicobacter pylori, the thermochemical values for these complexes showed that its high affinity for Mg2+ cations caused the hydration of Rho B. According to the results of the calculations, for Rho A–Ca2+(H2O)6, ΔH = −72.21 kcal mol−1; for Rho B–Ca2+(H2O)6, ΔH = −72.53 kcal mol−1; for Rho A–Mg2+(H2O)6, ΔH = −72.99 kcal mol−1 and for Rho B–Mg2+(H2O)6, ΔH = −95.00 kcal mol−1, confirming that Rho B binds most strongly with hydrated Mg2+, considering the energy associated with this binding process. This result suggests that Rho B forms a more stable complex than its isomer does with magnesium ion. Docking results show that both of these rhodostreptomycin molecules bind to solvated Ca2+ or Mg2+ through hydrogen bonding. Finally, Rho B is more stable than Rho A when protonation occurs.

The relationship between the chemical structure and biological activity (log IC50) of 40 derivatives of 1,4-dihydropyridines (DHPs) was studied using density functional theory (DFT) and multiple linear regression analysis methods. With the aim of improving the quantitative structure-activity relationship (QSAR) model, the reduced density gradient s( r) of the optimized equilibrium geometries was used as a descriptor to include weak non-covalent interactions. The QSAR model highlights the correlation between the log IC50 with highest molecular orbital energy (E HOMO), molecular volume (V), partition coefficient (log P), non-covalent interactions NCI(H4-G) and the dual descriptor [Δf(r)]. The model yielded values of R 2=79.57 and Q 2=69.67 that were validated with the next four internal analytical validations DK=0.076, DQ=-0.006, R P =0.056, and R N=0.000, and the external validation Q 2boot=64.26. The QSAR model found can be used to estimate biological activity with high reliability in new compounds based on a DHP series. Graphical abstract The good correlation between the log IC50 with the NCI (H4-G) estimated by the reduced density gradient approach of the DHP derivatives.

Herein we describe a straightforward method for the determination of the absolute configuration of 3-indolyl(bromo)acetate 7, 3-indolyl(alkoxy)acetates 8a–f and 3-indolyl(amino)acetate 8g, based on 1H NMR spectral analysis. The conformational preferences for two diastereomeric esters were calculated by DFT, which matched very well with the experimental results. X-ray diffraction analysis allowed us to validate the methodology, and independent absolute configuration evidence was obtained by vibrational circular dichroism.

Two series of heterocyclic tin compounds of general formula [(S{C6H3(CH2)nS}2O)SnR1R2] with different central ring sizes were prepared. The ten-membered series includes the compounds with n = 1 and R1 = R2 = Ph (5); R1 = Cl, R2 = Ph (6); R1 = Cl, R2 = n-Bu (7); R1 = R2 = Cl (8); the eight-membered series includes the compounds with n = 0 and R1 = R2 = Ph (10); R1 = Cl, R2 = n-Bu (11) and R1 = R2 = Cl (12). The compounds 5, 7, 8, 10, and 11 were investigated by single-crystal X-ray diffraction. The chloro compounds 7, 8, and 11 displayed a bipyramidal geometry at the tin atom with different degrees of distortion ranging from 57% to 62%. The diphenyl compounds 5 and 10 displayed a tetrahedral geometry at Sn. The conformation of the central ring in the ten-membered series is similar and is described as boat; the other series displayed two different conformations described as boat–chair and boat–boat. The possible conformers in the gas state of compounds 5, 7, 8, 10, 11, and 12 were investigated by MMFF, LSDA, BLYP, B3LYP, and M06 functionals using the DGDZVP and TZVP basis sets. The structural data of the total optimization agreed with the experimental results. The topological analysis indicated that bond critical points are present along the O⋯Sn direction in the compounds 7, 8, 11, and 12.

Dithiastannecine compounds of the type [{D(C6H4CH2S)2}SnR1R2] with different donor atoms D were prepared, where D = O and R1 = R2 = Ph (4a); R1 = Ph, R2 = Cl (5a); R1 = n-Bu, R2 = Cl (6a); D = S and R1 = R2 = Ph (4b); R1 = Ph, R2 = Cl (5b); R1 = n-Bu, R2 = Cl (6b). The molecular structures of the monochloro compounds 5a, 5b, 6a, and 6b were established by single-crystal X-ray diffraction and exhibit trigonal bipyramidal geometry at the tin atom with different degrees of distortion being due a D⋯Sn interaction. The spiro compounds [{D(C6H4CH2S)2}2Sn] with D = O (7a) and D = S (7b) were also synthesized and structurally characterized; the molecular structure of 7a showed the tin atom with a bicapped tetrahedral geometry. The behavior of all tin compounds in solution was investigated by NMR spectroscopy revealing that the D⋯Sn interaction in solution was practically absent on the basis of the NMR chemical shifts values. DFT calculations with ADF package using VWN/QZ4P were carried out for the 6a and 6b compounds and showed that, in the topological analysis, bond critical points are present along the D⋯Sn direction.

The straightforward determination of the absolute configuration of 2-oxo-3-indolylacetic acid derivatives 5a–e, based on analysis of the 1H NMR spectra of their oxindolylacetyl-phenyloxazolidinones 6a–e, is described. The conformational preferences for two diastereomeric amides were calculated by DFT, which matched well with the experimental results, while X-ray diffraction analysis allowed us to validate the methodology. Independent absolute configuration evidence was also obtained by vibrational circular dichroism.

The ruthenium complex with (N,N,N-tris(benzimidazol-2yl-methyl)amine, L(1)) was prepared, and characterized. Fukui data were used to localize the reactive sites on the ligand. The structural and electronic properties of the complex were analyzed by DFT in different oxidation states in order to evaluate its oxidant properties for phenol oxidation. The results show that the hard Ru(IV) cation bonds preferentially with a hard base (Namine = amine nitrogen, or axial chloride ion), and soft Ru(II) with a soft base (Nbzim = benzimidazole nitrogen or axial triphenyl phosphine). Furthermore, the Jahn-Teller effect causes an elongation of the axial bond in the octahedral structure. The bonding nature and the orbital contribution to the electronic transitions of the complex were studied. The experimental UV-visible bands were interpreted by using TD-DFT studies. The complex oxidizes phenol to benzoquinone in the presence of H2O2 and the intermediate was detected by HPLC and (13)C NMR. A possible mechanism and rate law are proposed for the oxidation. The adduct formation of phenol with [Ru(O)L(1)](2+) or [Ru(OH)L(1)](+) is theoretically analyzed to show that [Ru(OH)L(1)-OPh](+) could produce the phenol radical.