José María Rivera

Synthesis, characterization and nonlinear optical (NLO) properties of a push–pull bisboronate chromophore with a potential electric field induced NLO switch

A new bisboronate with five six-membered ring heterobicycles was prepared by reaction of [2-(2-hydroxy-4-diethylaminobenzylidene)amino]-5-nitroaminophenol and 1,4-phenyldiboronic acid, and its quadratic nonlinear optical (NLO) response was compared to that of a related monoboronate species. A computational investigation conducted within the framework of the DFT theory, at the B3PW91/6-31G* level, indicates that, while the diboronate derivative exhibits a centrosymmetric conformation in the ground state, and hence a vanishing quadratic hyperpolarizability (β), the application of an external electric field provides a gradual intramolecular rotation of the two “push–pull” sub-units which reaches 128° for a field intensity of 10−3 a.u. and leads to a β value equal to 49.2 × 10−30 cm5 esu−1. This result suggests a possibility for a molecular NLO switch induced by an electric field in such systems. Experimentally, the NLO response measured by the electric field induced second harmonic (EFISH) technique indicates an NLO response (expressed as the μ × β product) 1.95 times larger for the bisboronate than for the monoboronate analogue, thus suggesting that, although the ground state conformation is centrosymmetric, the “push–pull” sub-units are in quasi-free rotation at room temperature.

Highly Efficient Adsorption of Aqueous PbII with Mesoporous Metal-Organic Framework-5

1Facultad de Ciencias Quı́micas, Universidad Veracruzana, Prolongación Oriente 6, No. 1009 Colonia Rafael Alvarado, 94340 Orizaba, VER, Mexico 2Instituto Tecnológico de Mérida, Av. Tecnológico km 4.5, 97118 Mérida, YUC, Mexico 3Instituto Tecnológico de Cancún, DEPI, Av. Kabah km 3, 77500 Cancún, QROO, Mexico 4Facultad de Ingenieŕıa Quı́mica, Universidad Autónoma de Yucatán, Campus de Ingenieŕıas y Ciencias Exactas, Periférico Norte km 33.5, 97203 Mérida, YUC, MexicoMesoporous metal-organic framework-5 (MOF-5), with the composition Zn4O(BDC)3, showed a high capacity for the adsorptive removal of Pb(II) from 100% aqueous media. After the adsorption process, changes in both morphology and composition were detected using a scanning electron microscope (SEM) equipped with an energy dispersive X-ray (EDX) system, Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) analysis. The experimental evidence showed that Zn(II) liberation from MOF-5 structure was provoked by the water effect demonstrating that Pb(II) removal is not due to ionic exchange with Zn. A kinetic study showed that Pb(II) removal was carried out in 30 min with a behavior of pseudo-second-order kinetic model. The experimental data on Pb(II) adsorption were adequately fit by both the Langmuir and BET isotherm models with maximum adsorption capacities of 658.5 and 412.7 mg/g, respectively, at pH 5 and 45°C. The results of this work demonstrate that the use of MOF-5 has great potential for applications in environmental protection, especially regarding the removal of the lead present in industrial wastewaters and tap waters.

Bis(μ2-benzoato-κ2O:O′)bis­[(benzoato-κ2O,O′)bis(4,4′-bi­pyridine-κN)cobalt(II)]–benzoic acid (1/6)

In the title compound, [Co2(C7H5O2)4(C10H8N2)4]·6C6H5COOH, the centrosymmetric cobalt dimer co-crystallizes with six molecules of benzoic acid. Each CoII atom is coordinated by four O atoms in a distorted square-planar arrangement while the N atoms are located in apical positions. The dihedral angles between the rings comprising each of the 4,4′-bipyridyl ligands are 25.2 (2) and 22.8 (2)°. In the crystal, the three-dimensional network is assembled by O—H⋯O and C—H⋯O hydrogen bonds.

Synthesis, characterization and X-ray studies of new six–seven membered rings [4.5.0] heterobicyclic system of monomeric boronates

Abstract Different tridentate ligands derived from ethanolamines and 2-hydroxyacetophenone, 2-hydroxybenzophenone and salicylaldehyde were reacted with two equivalents of phenylboronic acid to obtain compounds 6a–6f which are [4.5.0] heterobicyclic systems with a B−O−B structural unit. The boronates were fully characterized and two heterobicyclic [4.5.0] structures have been analyzed by X-ray crystallography, where a series of parameters such as bond distances, bond angles, torsion angles, tetrahedral character at the boron atom and deviation of the boron atom from the mean plane have been evaluated.

Crystal structure of catena-poly[[[tri­aqua­(4-cyano­benzoato-κO)nickel(II)]-μ-4,4′-bi­pyridine-κ2N:N′] 4-cyano­benzoate]

In the title polymeric complex salt, {[Ni(C8H4NO2)(C10H8N2)(H2O)3](C8H4NO2)}n, the NiII cation is coordinated by a 4-cyanobenzoate anion, two 4,4′-bipyridine ligands and three water molecules in a distorted N2O4 octahedral geometry. The 4,4′-bipyridine ligands bridge the NiII cations to form polymeric chains of the title complex cations, propagating along the c-axis direction. The dihedral angle between the pyridine rings of the 4,4′-bipyridine ligand is 24.9 (6)°. In the crystal, the uncoordinating 4-cyanobenzoate anions link with the complex cations via O—H⋯O hydrogen bonds into a three-dimensional supramolecular architecture. Weak C—H⋯O, C—H⋯N interactions and π–π stacking [centroid-to-centroid distances = 3.566 (4) and 3.885 (4) Å] are also observed in the crystal.