Héctor García-Ortega

Optical properties of two fluorene derived BODIPY molecular rotors as fluorescent ratiometric viscosity probes

BODIPY-derived molecular fluorescent rotors are one of the most useful families of fluorescent probes for the quantitative measurement of microviscosity. Here, we report the photophysical properties of two molecular rotors as ratiometric viscosity sensors, meso-(4-(9H-fluoren-2-yl)ethynyl)phenyl-4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (1) and meso-(5-(9H-fluoren-2-yl)ethynyl)thiophen-2-yl-4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (2) having two independent chromophores; one (fluorene) is not influenced by viscosity and is used to determine concentration properties, and the other chromophore (BODIPY) acts as a molecular rotor. The fluorescence ratiometric calibration against microviscosity for the most sensitive probe (1), was obtained in a wide linear dynamic range. The sensitivity of the spectroscopic observables for 1 and 2 towards solvent viscosity and the typical analytical interfering solvent polarity and polarizability parameters were investigated by means of two different solvent scales, namely Lippert–Mataga and Catalan, finding consistent results. Quantum chemical calculations were conducted to analyze the probe mechanism in terms of Natural Transition Orbitals (NTOs) and the spatial extent of charge transfer excitations.

Structure and Electronic Conductivity of Reduced Gd-Doped CeO2

In this work we studied the electronic conductivity of highly reduced polycrystalline Ce 0.8 Gd 0.2 O 1.9-8 at low temperatures (25-100°C). The specimens were treated at a variety of reducing conditions at high temperature and then quenched. The nonstoichiometry of the samples was estimated by thermogravimetry. We showed that a high reduction level leads to high conductivity and low activation energy. We estimated an activation energy change from 0.60 to 0.38 eV in going from slightly to heavily reduced. An X-ray diffraction study of this nonstoichiometric material showed that the reduction is accompanied by an increase of a secondary bixbyite phase. If the quenched structures studied in this work represent the high-temperature phases, then our results are in contradiction to models that consider that the fluorite structure of CeO 2 is highly tolerant to reduction remaining as a single phase.

Coumarin Derivative Directly Coordinated to Lanthanides Acts as an Excellent Antenna for UV–Vis and Near-IR Emission

A chelating coumarin-derived ligand sensitizes all emitting lanthanide ions in the solid state and gives high absolute quantum yields for ethanol solutions of complexes of Sm, Eu, Tb, and Dy, above 20% for the last two. Crystal structures of these four complexes are [Ln(Cum)3(H2O)(X)]·X where X = MeOH or EtOH.

Bis(4-nitroanilines) in interactions through a π-conjugated bridge: conformational effects and potential molecular switches

Two molecules, 2,2′-(1,4-phenylenebis(ethyne-2,1-diyl))bis(4-nitroaniline) (PNA) and 2,2′-(1,4-phenylene-bis(ethyne-2,1-diyl))bis(N,N-diethyl-4-nitroaniline) (PDNA), built up from two p-nitroaniline “push–pull” nonlinear optical (NLO) chromophores slightly conjugated through a 1,4-phenylenebis(ethyne-2,1-diyl) bridge have been synthesized and fully characterized. The crystal structure of PNA reveals that the ground (off) state conformation corresponds to the centrosymmetric anti-conformer in which the molecular hyperpolarizability (β) is equal to zero. A computational investigation reveals that, once submitted to an intense electric field (E), the two p-nitroaniline subunits are gradually aligned in the direction of the field with the appearance of a metastable (on) state (β ≠ 0, when E = 0), stabilized by conjugation. A loop of hysteresis is observed during the on off cycles leading to a form of molecular bistability. The NLO response of PNA has been investigated at different field intensities by the electric-field induced second-harmonic (EFISH) technique to provide experimental evidence for this behavior.

Crystal structure of the chalcone (E)-3-(furan-2-yl)-1-phenylprop-2-en-1-one.

The crystal packing of the compound is described by an intermolecular arrangement with the molecules as interlaced layers in a zigzag fashion, denoting interacting self-complementary dimers mainly by the localization of weak hydrogen bonds in a head-to-tail arrangement.

Structural and morphological studies of meso-ethylcarbazole F-BODIPY thin films

In this work, we describe the synthesis of meso-(9-ethyl-9H-carbazol-3-yl)-4,4-difluoro-4-bora-3a,4a-diaza-s-indacene and its incorporation as thin film by vapor deposition on indium tin oxide. The morphology of the film was analyzed by scanning electron microscopy and atomic force microscopy showing a granular and homogeneous structure, contact angle measurements revealed that this film exhibits a hydrophobic surface. Packing of the compound was simulated through molecular dynamics and Monte Carlo sampling, and the electronic features of aggregates were modeled with plane-wave DFT. A semiconductor behavior for the featured compound in aggregated state, which compares well with systems applied on electronic devices, is predicted for the featured F-BODIPY.Graphical Abstract

Design, synthesis, in vitro evaluation and preliminary SAR studies of N-(2-(heteroaryloxy)propyl)phenothiazines against Rhipicephalus microplus cattle tick.

A family of 15 N-substituted phenothiazines was designed, synthesized and their acaricidal activity against Rhipicephalus microplus was determined in vitro. The synthetic methodology is simple and can be employed in multigram scale. The rationale for the structure-based design of these compounds is the potential for azines and phenothiazine to engage in π-π interactions; these fragments, joined together by a short, flexible alkoxide linker, structurally resemble phenothiazine-based cholinesterase inhibitors, while their weak basicity implies a neutral active form, rather than a cationic one, thus facilitating penetration of the cuticle of ticks. One compound displayed excellent acaricidal activity (LD50=0.58 μg/mL). Preliminary SAR analysis suggests that the activity is influenced by the presence of a weakly basic nitrogen atom, as well as the substitution pattern within the heterocycles.

exo-1,7-Dimethyl-4-phenyl-10-oxa-4-aza­tri­cyclo­[5.2.1.02,6]dec-8-ene-3,5-dione

The title compound, C16H15NO3, consists of an oxabicycle fused to an N-phenyl-substituted pyrrolidine ring anti to the double bond, affording the exo isomer. In the oxabicycle system, the six-membered ring presents a boat conformation, while the heterocyclic rings show envelope conformations with the O atom projected out of the plane. In the crystal, adjacent molecules are linked via weak C—H⋯O hydrogen bonds, forming chains propagating along the a-axis direction. The chains are linked by C—H⋯π interactions, forming two-dimensional networks lying parallel to the ac plane.

Synthesis of Novel Pyridinium Betaine Precursors from exo-Norbornene Dicarboximides

N-heterocyclic norbornene Dicarboximides were synthesized by reacting the exo-norbornene-5,6-dicarboxylic anhydride with 2-, 3-, and 4-aminopyridine. The amides resulting from 3 and 4-aminopyridine derivatives were converted into the corresponding betaines via Menshutkin reaction using ethyl-bromoacetate. The chemical structures of the obtained products were confirmed by FT-IR and 1 H and 13 C NMR spectroscopy, EA and MS as well as by calculation of 1 H and 13 C NMR chemical shifts using the GIAO method (PW91/6-311G++ (3df, 3pd) approximation by GAUSSIAN and PW91/IGLO-III approximation by deMon2k).