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Se reporta la determinación de los orbitales frontera (HOMO y LUMO) de un par de compuestos organometálicos (PdCl2L y PdBr2L). Este tipo de compuestos han cobrado gran interés por sus prometedores propiedades y aplicación en optoelectrónica, ya que combinan las ventajas de los materiales orgánicos e inorgánicos, su potencial uso está determinado en gran parte por los valores de sus orbitales frontera. Entre los métodos utilizados para conocer esta información, se considera a la voltamperometría cíclica, la cual permite determinar de forma indirecta dichos niveles de energía mediante la determinación los potenciales del comienzo de los procesos de oxidación y reducción de las moléculas en estudio. Los complejos PdCl2L y PdBr2L fueron caracterizados por el método mencionado, con los datos obtenidos se procedió al cálculo de los orbitales frontera y el bandgap. De acuerdo con los resultados, los valores se encuentran dentro del rango reportado para semiconductores, indicando que los complejos son viables para ser empleados en la fabricación de dispositivos optoelectrónicos.

The chemistry of multinuclear metal complexes bearing by N-heterocyclic carbene (NHC) ligands, is an area of fast growing interest in modern organometallic chemistry. In particular, complexes supported by mesoionic (MIC) 1,2,3-triazolylidenes are attracting a great deal attention due to their postulated superior donor capacity compared to classical NHC ligands. Despite the readily available synthetic routes to MIC-based ligand platforms featuring several substitution levels, most of the coordination chemistry of triazolylidenes is still dominated by mononuclear complexes. In this short review article, recent progress on the design and synthesis of multinuclear triazolylidene complexes (ranging from di- to tetranuclear species) is discussed. Special emphasis is placed on their structural features, electronic properties and catalytic applications.

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.

A ferrocenyl chalcone (OFcPV) with attractive optical and magnetic properties for its potential application in optoelectronic devices, excellent processability in solution, and thermal stability is reported. It was derived from the synthesis of ferrocenyl chalcone with different degrees of conjugation and the preliminary selection of the most attractive molecule based on its linear optical and electrochemical properties, and processability. Three ferrocene-derived compounds: a low-molecular weight molecule (3FcPV), an oligomer (OFcPV), and a polymer (PFcPV) were synthesized through Friedel–Crafts reactions and aldol condensations. The chemical structure of the compounds has been elucidated by proton nuclear magnetic resonance and Fourier-transform infrared spectroscopies. UV–Vis and fluorescence spectroscopies were used to evaluate the optical properties of these new compounds. The frontier orbitals levels of the materials deposited as films were determined using cyclic voltammetry. The optical bandgaps for 3FcPV, OFcPV, and PFcPV were 2.8, 2.4, and 2.36 eV, respectively. These results place these materials within the organic semiconductors and evidence the influence of the degree of electronic conjugation of the molecule in the reduction of the bandgap. The results showed that the oligomer and the polymer possess similar electronic and optical properties. However, the oligomer solubility improves the processability necessary for the manufacturing photonic devices. OFcPV was characterized by Z-scan technique, and the results indicate that OFcPV is candidate to be used as an optical limiter, fast optical switch, or optical logic gates. Also, OFcPV exhibits quasi-superparamagnetic behavior resulting from the iron disposal in the structure.

La importancia de los complejos organometálicos de iridio, reside en su uso como materiales híbridos orgánico-inorgánicos, para la formación de polímeros que contengan centros metálicos. Estos compuestos son de gran interés no sólo en la industria de los polímeros, sino también en la industria química primaria y secundaria por su potencial aplicación en procesos de catálisis. El éxito de estos compuestos reside en la capacidad de introducir complejos metálicos con cadenas poliméricas, los cuales pueden darle en particular diferentes atributos tales como actividad catalítica, entre otras. En el presente trabajo se reporta la síntesis de un nuevo compuesto organometálico de iridio (8). Para estabilizar la esfera de coordinación del metal se utilizó el ligante polidentado, del tipo hidrotris-(3,5-dimet il-1-pirazolil)borato, [HB-(3,5-Mepz)3],1 que generalmente confiere una elevada estabilidad a los complejos que forman, permitiendo el desarrollo de diferentes procesos en las restantes posiciones de coordinación. El tema fundamental de estudio es la activación de enlaces C-H2 y otros C-C, de sustancias orgánicas como la alildifenilfosfina. El material de partida fue el complejo del tipo 2,3-dimetilbutadieno de iridio TpMe2Ir(CH2CMe=CMeCH2)3 [1], el cual reaccionó con 1 equivalente de alildifenilfosfina a 60 °C durante 24 h, obteniéndose el complejo del tipo h1-h1-buteno-diilo-alildifenilfosfina de iridio (8). El compuesto (8) fue un sólido cristalino blanco, en el que se incorporó una molécula de alildifenilfosfina a la esfera de coordinación del metal. La elucidación del complejo organometálico de alilfosfina se llevó a cabo mediante caracterización por RMN de 1H y 13C.

Human milk oligosaccharides (HMO) have attracted great interest in recent years due to their role in boosting infants and adults health. According to several in vitro, in vivo and clinical studies,...

Treatment of NHC-AuCl (NHC = IPr and IMes) complexes with equimolar amounts of KTpR2 (R = Me, H) salts in tetrahydrofuran produces in high yields the heteroleptic complexes 3-6 with the general formula NHC-Au-TpR2. As the TpR ligand in complexes 3-6 features a k1-N type coordination toward the gold(i) center, the subsequent addition of group 10 and 11 metal precursors (NiII, PtII, CuII) results in the isolation of heterobimetallic Au/M complexes supported by TpR platforms. All new metal complexes have been fully characterized by elemental analysis and NMR spectroscopy, and in the case of 3, 4 and 6 by X-ray crystallography.

This work presents a novel electrochemical sensor for methanol, based on a Cu(II) Metal-Organic Framework. The copper (II) benzenetricarboxylic metal-organic framework (Cu-BTC) was synthesized in mild condition at room temperature, and the obtained crystals were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). The obtained Cu-BTC was incorporated at different ratios (7, 15, 30 wt%) in carbon paste electrodes to determine its electrocatalytic activity in the absence and the presence of methanol. The electrodes were characterized by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). An anodic peak response toward methanol was observed at 1.25 V using 0.1 M NaOH as supporting electrolyte, with a maximum current density of 10 mA. Also, the oxidation signal of methanol in the presence of ethanol was studied by DPV. The quantitative analysis of methanol in the presence of ethanol using the modified electrode presented a LOD, LOQ and sensitivity values of 0.0511 mM, 0.1549 mM, and 19.8 mA mM−1 cm−2, respectively. The results demonstrated the high potential of Cu-BTC as part of electrochemical sensors for the determination of methanol in actual samples.

The synthesis and full characterization of a new series of p-tert-butylcalix [7]arene (tBuC7) monoanions of the type tBuC7•M (M = Na, K, Rb, Cs) is reported. Crystal structures of tBuC7•K and tBuC7•Rb feature monomeric units and represent the first examples of solid state characterized tBuC7 salts. The alkali metal base strength and reaction stoichiometry used for the selective formation of monoanionic species is discussed.

In the quest of heteroleptic gold(I) complexes containing triazolylidenes (MIC) and TpMe2 ligands, we discovered that reaction of the MIC–Au–I complex 2 with potassium hydrotris-(3,5-dimethyl-1-pyrazolil) borate (KTpMe2) produces an unexpected bis(triazolylidene) gold(I) complex featuring a large [(TpMe2)2K] anion (3). An optimized synthesis was achieved by reacting a preformed bis(triazolylidene)Au(I) complex (2a) with two equivalents of KTpMe2 (81%). Full characterization and preliminary catalytic results demonstrate the high performance of complex 3 in the formation of several oxazoline derivatives.

The facile preparation of a C4-symmteric tetratriazolium salt and its subsequent metalation to generate a series of tetranuclear mesoionic carbene gold(I) complexes is presented. The complete structural characterization of the metallic carbenes and the benefits of cooperative catalysis in the processes of hydroamination and hydrohydrazination of terminal alkynes are discussed.

Coordination complexes and metal–organic frameworks are compounds with unlimited applications in electrochemistry. Those based on Co, Ni, and Cu offer redox-active properties that can be an advantage for the electro-oxidation of short-chain alcohols in alkaline media. At the present, there is a crescent interest for its application in direct methanol fuel cells and a big effort is being carried out to improve the oxidation potentials obtained with these compounds before their practical uses as DMFCs anodes. Herein, we collected the recent advance on the use of coordination compounds (coordination complexes and Metal-Organic Frameworks) as modifiers for electrodes and their evaluation on methanol electro-oxidation in alkaline media. Fundamental aspects of the key role of coordination compounds in electro-oxidation, the fabrication of modified electrodes containing coordination compounds, and diverse examples of its use of methanol electro-oxidation will be discussed.

Since ancient times, ginger (Zingiber officinale) has been widely used for culinary and medicinal purposes. This rhizome possesses several chemical constituents; most of them present antioxidant capacity due mainly to the presence of phenolic compounds. Thus, the physical conditions for the optimal extraction of antioxidant components of ginger were investigated by applying a Box-Behnken experimental design. Extracts of ginger were prepared using water as solvent in a conventional solid–liquid extraction. The analyzed variables were time (5, 15 and 25 min), temperature (20, 55 and 90 °C) and sample concentration (2, 6 and 10 %). The antioxidant activity was measured using the 2,2-diphenyl-1-picrylhydrazyl method and a modified ferric reducing antioxidant power assay while total phenolics were measured by Folin & Ciocalteu’s method. The suggested experimental design allowed the acquisition of aqueous extracts of ginger with diverse antioxidant activity (100–555 mg Trolox/100 g, 147–1237 mg Fe2+/100 g and 50–332 mg gallic acid/100 g). Temperature was the determining factor in the extraction of components with antioxidant activity, regardless of time and sample quantity. The optimal physical conditions that allowed the highest antioxidant activity were: 90 °C, 15 min and 2 % of the sample. The correlation value between the antioxidant activity by ferric reducing antioxidant power assay and the content of total phenolics was R2 = 0.83. The experimental design applied allowed the determination of the physical conditions under which ginger aqueous extracts liberate compounds with antioxidant activity. Most of them are of the phenolic type as it was demonstrated through the correlation established between different methods used to measure antioxidant capacity.

The design, synthesis and characterization of a series of dithioether ligands featuring two di-(2-picolyl)amine arms (2a–2d) and their corresponding cationic dinuclear palladium (II) complexes (3a–d) are reported. Crystal structures of ligand 2b and complexes 3b and 3d were determined by X-ray diffraction studies. The molecular structures of 3b and 3d display each of the two di-(2-picolyl)amine fragments coordinated to one palladium(II) atom in a (κ3-N,N,N) tridentate fashion and with the cationic metal centers displaying square-planar geometries. Weak interactions between the metal centers and the thioether fragments are observed. All bimetallic complexes 3a–d were tested as catalytic precursors in the Suzuki couplings of different o- or p-substituted iodo- or bromoaryls with boronic acids. The overall catalytic results indicate that complex 3b is the best precursor of the series demonstrating even more efficient performance compared to commercial palladium sources such as Pd(OAc)2 and the Najera Catalysts.

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.

The reaction of 4-substituted imidazol-2-ylidenes with various electrophiles produces a series of 2,4-functionalized imidazolium salts. Subsequent metalation of these precursors using AuCl(SMe2) provides the first examples of highly functionalized abnormal carbenegold(I) complexes. The present protocol introduces a new strategy for the synthesis of metallic abnormal carbenes featuring diverse functional groups

Synthesis and structural characterization of cis -dichlorocomplexes derived from 2-pyridylmethyl- N -methylimine ( 1 ), 2-pyridylmethyl- N -ethylimine ( 2 ), and 2-pyridylmethyl- N -(2-bromophenyl)imine ( 3 ) of general formula [M II {(C 5 H 4 N)–C(H) NR} n Cl 2 ] {M = Ni, Pd, Pt; R = Me, Et, –(2-Br–C 6 H 4 ); n = 1, 2} are described. Paramagnetic complexes of Ni II ( 1a – 3a ) were identified by elemental analyses, vibrational spectroscopy and for 2a and 3a , by electronic spectroscopy; the complexes of Pd II ( 1b – 3b ) and Pt II ( 1c – 3c ) were characterized by elemental analyses, vibrational spectroscopy and NMR. X-ray molecular structures of 1a , 2a , 1b – 3b , 2c and 3c displayed a bidentate coordination mode of the N -substituted pyridylimines ( 1 – 3 ) towards the metallic atoms with the formation of five-membered chelate rings and the chlorine atoms in a cis coordination. In 1a and 2a a distorted octahedral local geometry around the nickel atom was observed, whereas a distorted square planar local geometry around the palladium and platinum atoms in the compounds 1b – 3b , 2c and 3c was displayed.

The Ir(i) complexes [Tp

In the title complex salt, [Ir(C5H4O)(C16H22N6)(CO)](CF3O3S), the IrIIIcentre adopts a distorted octahedral geometry with a facial coordination of the tris(3,5-dimethyl-1H-pyrazol-1-yl)methane ligand. The C—C distances of the iridacycle are in agreement with its iridacyclohexa-2,5-dien-4-one nature, which presents a nonsymmetric boat-like conformation with the C—Ir—C vertex more bent than the C—C(=O)—C vertex. The supramolecular architecture is mainly directed by CO...CO and CO...π and Csp3—H...O interactions, the arrangement of which depends on the anion.

We have determined the preferred conformers in solution by a detailed NMR analysis using COSY and HETCOR experiments of three inositol isomers: myo (1), scyllo (2) and epi (3) plus sixteen derivatives of myo-inositol: 1,2,3,4,5,6-hexa-O-acetyl-myo-inositol (4), 1,2,-O-isopropylidene-myo-inositol (5), 1,2:4,5-di-O-isopropylidene-myo-inositol (6), 3,4,5,6-tetra-O-acetyl-1,2-O-isopropylidene-myo-inositol (7), 3,4,5,6-tetra-O-acetyl-myo-inositol (8), 1,2-O-isopropylidene-3,6-di-O-tosyl-myo-inositol (9), 1,2-O-isopropylidene-3,4,6-tri-O-tosyl-myo-inositol (10), 1,2:4,5-di-O-isopropylidene-3-O-tosyl-myo-inositol (11), 3,6-di-O-benzyl, 1,2:4,5-di-O-isopropylidene-myo-inositol (12), 3,6-di-O-benzyl-1,2-O-isopropylidene-myo-inositol (13), 3,6-di-O-benzyl-myo-inositol (14), 1,2-O-cyclohexylidene-myo-inositol (15), 1,2:4,5-di-O-cyclohexylidene-myo-inositol (16), 1,2:5,6-di-O-cyclohexylidene-myo-inositol (17), 1,3,5-O-(orthoformate)-myo-inositol (18) and 2-benzyl-1,3,5-O-(orthoformate)-myo-inositol (19). The...

Molecules of 1,2-bis(4-bromophenyl)-1H-benzimidazole, C19H12Br2N2, (I), and 2-(4-bromophenyl)-1-(4-nitrophenyl)-1H-benzimidazole, C19H12BrN3O2, (II), are arranged in dimeric units through C—H...N and parallel-displaced π-stacking interactions favoured by the appropriate disposition of N- and C-bonded phenyl rings with respect to the mean benzimidazole plane. The molecular packing of the dimers of (I) and (II) arises by the concurrence of a diverse set of weak intermolecular C—X...D(X= H, NO2;D= O, π) interactions.

We have prepared two new tetracyclic phenylboronic esters 4 and 5 derived from myo-inositol and from 1,2-O-isopropylidene-myo-inositol, respectively. The structures of these compounds were established from NMR and IR spectra, elemental analyses, and an X-ray diffraction study in the case of 4. Compound 4 is a tetracyclic derivative of the less stable conformer of inositol (five axial hydroxy groups and one equatorial) with two dioxaboroline rings at opposite faces of the six-membered ring, one formed between the boron atom and the axial hydroxyl groups at C-3 and C-5 and the other between the boron atom and the hydroxyl groups at C-4 and C-6, and a dioxaborolidine ring bridging C-1 and C-2 at axial and equatorial positions. A similar structure was found for 5 with the difference that bridging C-1 and C-2 there is a dioxolane ring. The boron atoms are planar with their attached atoms, stabilized by retrocoordination between the boron and oxygen and carbon atoms, respectively. The two phenyl rings that are in the same face of the molecule are essentially parallel, with a dihedral angle between planes of 28.26 ± 0.79°.

We have determined the preferred conformers in solution by a detailed NMR analysis using COSY and HETCOR experiments of three inositol isomers: myo (1), scyllo (2) and epi (3) plus sixteen derivatives of myo-inositol: 1,2,3,4,5,6-hexa-O-acetyl-myo-inositol (4), 1,2,-O-isopropylidene-myo-inositol (5), 1,2:4,5-di-O-isopropylidene-myo-inositol (6), 3,4,5,6-tetra-O-acetyl-1,2-O-isopropylidene-myo-inositol (7), 3,4,5,6-tetra-O-acetyl-myo-inositol (8), 1,2-O-isopropylidene-3,6-di-O-tosyl-myo-inositol (9), 1,2-O-isopropylidene-3,4,6-tri-O-tosyl-myo-inositol (10), 1,2:4,5-di-O-isopropylidene-3-O-tosyl-myo-inositol (11), 3,6-di-O-benzyl, 1,2:4,5-di-O-isopropylidene-myo-inositol (12), 3,6-di-O-benzyl-1,2-O-isopropylidene-myo-inositol (13), 3,6-di-O-benzyl-myo-inositol (14), 1,2-O-cyclohexylidene-myo-inositol (15), 1,2:4,5-di-O-cyclohexylidene-myo-inositol (16), 1,2:5,6-di-O-cyclohexylidene-myo-inositol (17), 1,3,5-O-(orthoformate)-myo-inositol (18) and 2-benzyl-1,3,5-O-(orthoformate)-myo-inositol (19). The...