Matrix isolation FTIR spectroscopic and theoretical study of 3,3-dichloro-1,1,1-trifluoropropane (HCFC-243)

The molecular structure and infrared spectrum of the atmospheric pollutant 3,3-dichloro-1,1,1-trifluoropropane (HCFC-243) were characterized experimentally and theoretically. The theoretical calculations show the existence of two conformers, with the gauche (G) and trans (T) orientation around the HCCC dihedral angle. Conformer G was calculated to be more stable than form T by more than 10 kJ mol (-1). In consonance with the large predicted relative energy of conformer T, only the G form was identified spectroscopically in cryogenic argon (10 K) and xenon (20 K) matrices prepared from room-temperature equilibrium vapor of the compound. The observed infrared spectra of the matrix-isolated HCFC-243 were interpreted with the aid of high-level density functional theory calculations and normal coordinate analysis. For experimental identification of the weakest IR absorption bands, the spectrum of HCFC-243 in the neat solid state at 145 K was obtained. This spectrum also confirmed the sole presence of the G conformer in the sample. Natural bond orbital and atomic charge analyses were carried out for the two conformers to shed light on the most important intramolecular interactions in the two conformers, in particular those responsible for their relative stability.     

N,N-Di-iso-propylcarbamato complexes of boron

N,N-di- iso-propylcarbamato derivatives of boron(III) have been synthesized from di-iso-propylamine and boron trichloride in the presence of carbon dioxide. With a large excess of amine, a single boron product was obtained, [NH2i)Pr2][B(O2CNiPr2)4], 1, while with a lower excess a mixture of 1 and of the dinuclear derivative [B2(O2CNiPr2)6], 2, was produced. By heating in vacuo at 60 degrees C, solid 1 slowly converted to 2. The transformation was reversible, 2 giving 1 back with di- iso-propylamine under carbon dioxide at atmospheric pressure. The molecular structure of both compounds was established by X-ray diffraction methods. Compound 1 is constituted by ion-pairs where the ammonium cation is hydrogen-bonded to the mononuclear anion. Compound 2 is a dinuclear species with two bridging carbamato ligands. In both derivatives, boron shows tetrahedral coordination. As IR- and 1H NMR spectra of the two species are well differentiated, it is possible to monitor the interconversion of 1 and 2 by both spectroscopic methods.     

Preclinical pharmacokinetics comparison between resveratrol 2-hydroxypropyl-β-cyclodextrin complex and resveratrol suspension after oral administration

Trans-Resveratrol (RV) is a natural polyphenol characterized by interesting pleiotropic potentials and health benefits, but its administration is hampered by a unsatisfactory pharmacokinetics. Various approaches have been identified to circumvent it: among them, 2-hydroxypropyl-β-cyclodextrins (HPβCD) are valuable strategy. Here, we compare the employment of HPβCD based formulation with a resveratrol nanosupension (obtained by diluting a RV ethanol solution with PBS, added of 0.05 % hydroxyethylcellulose) to improve RV bioavailability after oral administration to mice. The inclusion of RV in HPβCD was confirmed by differential scanning calorimetry, Fourier transformed infrared spectroscopy, and phase solubility study. The two formulations were orally administered to BALB-c mice. RV concentrations in plasma and tissues were detected at different time (0–120 min) by HPLC method. HPβCD complexation mediate a approximately fourfold increment in plasma RV C_max and  approximately twofold augment of RV AUC_0-120 in comparison with RV nanosuspension. Similar increased concentrations were observed in heart, liver, kidney and gut. In particular, HPβCD mediated a 5.5-folds increase of resveratrol concentration in the intestine, in comparison to the nanosuspension. In conclusion, based on our results, HPβCD complexation is a promising approach to increase the oral bioavailability of RV. Moreover, the achievement of high concentrations in gut suggested a potential employment of oral RV-HPβCD as anti-inflammatory/chemopreventive agent in this tissue.     

Dissociation of ground and nsigma* states of CF3Cl using multireference configuration interaction with singles and doubles and with multireference average quadratic coupled cluster extensivity corrections

Extended complete active space self-consistent field (CASSCF), multireference configuration interaction with singles and doubles (MR-CISD), and multireference average quadratic coupled cluster (MR-AQCC) calculations have been performed on the ground (S(0)) and first excited (nsigma(*),S(1)) states of the CF(3)Cl molecule. Full geometry optimizations have been carried out for S(0) as well as "relaxed" potential energy calculations for both states, along the C-Cl bond distance. Vertical excitation energies (DeltaE(vertical)), dissociation energies (DeltaE(diss)), dissociation enthalpies (DeltaH(diss)), and the oscillator strength (f) have also been computed. Basis set effects, basis set superposition error (BSSE), and spin-orbit and size-extensivity corrections have also been considered. The general agreement between theoretical and available experimental results is very good. The best results for the equilibrium geometrical parameters of S(0) (at MR-AQCCaug-cc-pVTZ+d level) are 1.762 and 1.323 A, for the C-Cl and C-F bond distances, respectively, while the corresponding experimental values are 1.751 and 1.328 A. The [angle](ClCF) and [angle](FCF) bond angles are in excellent agreement with the corresponding experimental values (110.3 degrees and 108.6 degrees ). The best calculated values for DeltaE(vertical), DeltaH(diss), and f are 7.63 eV [at the MR-AQCCaug-cc-pV(T+d)Z level], 3.59 eV[MR-AQCCaug-cc-pV(T+d)Z level+spin-orbit and BSSE corrections], and 2.74x10(-3) (MR-CISD/cc-pVTZ), in comparison with the corresponding experimental values of 7.7+/-0.1 eV, 3.68 eV, and 3.12 x 10(-3)+/-2.50 x 10(-4). The results concerning the potential energy curves for S(0) and S(1) show a tendency toward the nonoccurrence of crossing between these two states (in the intermediate region along the C-Cl coordinate), as the basis set size increases. Such tendency is accompanied by a decreasing well depth for the S(1) state. Dynamic electronic correlation (especially at the MR-AQCC level) is also an important factor toward an absence of crossing along the C-Cl coordinate. Further investigations of a possible crossing using gradient driven techniques (at CASSCF and MR-CISD levels) seem to confirm its absence.     

Electron paramagnetic resonance of Er doped in YVO4: hyperfine parameters

X-band (9.60 GHz) electron paramagnetic resonance (EPR) spectra of the Er³⁺ Kramers ion substituting for the Y³⁺ ion in yttrium vanadate (YVO₄) single crystal were recorded at liquid-helium temperatures. Fine and hyperfine EPR transitions were observed for the ¹⁶⁶Er (zero nuclear magnetic moment) and ¹⁶⁷Er (I=7/2) isotopes, respectively. The values of the elements of the anisotropic ²- and ò-tensors of the ¹⁶⁷Er³⁺ ion, and those of the ² tensor for the ¹⁶⁶Er ion, were estimated. The admixture of crystal-field wave functions in the ground-state wave function of Er³⁺ were determined using the experimental g-values.     

Single‐Walled Carbon Nanotubes in Highly Viscous Media: A Comparison between the Dispersive Agents [BMIM][BF4], L121, and Triton X‐100

Dispersions of single‐walled carbon nanotubes (SWNTs) have been prepared by using the room‐temperature ionic liquid [BMIM][BF₄] (1‐butyl‐3‐methylimidazolium tetrafluoroborate), the triblock copolymer Pluronic L121 [poly(ethylene oxide)₅‐poly(propylene oxide)₆₈‐poly(ethylene oxide)₅] and the non‐ionic surfactant Triton X‐100 (TX100) in the pure state. The size of the SWNTs aggregates and the dispersion degree in the three viscous systems depend on the sonication time, as highlighted by UV/Vis/NIR spectroscopy and optical microscopy analysis. A nonlinear increase in conductivity can be observed as a function of the SWNTs loading, as suggested by electrochemical impedance spectroscopy. The generation of a three‐dimensional network of SWNTs showing a viscoelastic gel‐like behavior above a critical percolation concentration has been found at 25 °C in all the investigated systems by oscillatory rheology measurements.