Rotational isomerization of small carboxylic acids isolated in argon matrices: Tunnelling and quantum yields for the photoinduced processes

The quantum yields for internal rotation around the C–O bond induced by excitation of the first overtone of the hydroxyl stretching mode in formic, acetic, and propionic acids isolated in solid Ar are comparatively discussed. The tunnelling kinetics for isomerization from the higher energy arrangement of the carboxylic group (cis) to the lower energy arrangement (trans) in this series of compounds is also analysed. Finally, the quantum yield for the Cα–C isomerization in propionic acid was investigated and, in contrast with the C–O isomerization, shown to be probably sensitive to the local matrix morphology

Infrared-Induced Rotamerization of Oxalic Acid Monomer in Argon Matrix

Infrared-induced conformational isomerization of oxalic acid monomer isolated in an argon matrix at 7.5 K was studied by infrared spectroscopy. For the first time, three conformational states of this molecule were identified experimentally and their vibrational spectra are assigned. In good agreement with density functional theory predictions, all the observed conformers exhibit a trans OC−CO axis, differing in the relative conformation of their O−C−O−H axes. In the most stable conformer (belonging to the C2h symmetry point group), two intramolecular OH···O hydrogen bonds are present. The second (Cs) most stable conformer shows a single OH···O bond, and the third one (C2h) does not exhibit any intramolecular hydrogen bond. Using narrowband tunable irradiation in the near-infrared region it was possible to promote very efficiently conformer interconversions, which was followed spectroscopically

Low temperature matrix-isolation and solid state vibrational spectra of tetrazole

Infrared spectra of tetrazole (CN isolated in an argon matrix (T \10 K) and in the solid state (at room 4H2) temperature) were investigated. In the crystalline phase, tetrazole exists in its 1H-tautomeric form and new assignments of the vibrational spectra (both infrared and Raman) of this phase are presented. The infrared spectrum of the matrix-isolated monomeric form of tetrazole is now reported and assigned for the Ðrst time, showing essentially the expected signature of the 2H-tetrazole tautomer. From relative intensities of the infrared bands ascribable to the two tautomers, the amount of the 1H-tautomer in the argon matrix was estimated to be ca. 10% of the most stable tautomer. Assuming that gas-phase relative populations of the two tautomers could be efficiently trapped in the argon matrix during deposition, the energy di erence between 1H- and 2H-tetrazole (*E was then obtained. The experimental value, kJ mol~1, 1Hh2H) *E1Hh2H\6.95^1.50 now determined for the Ðrst time, compares fairly well with the theoretical predictions for the molecule in vacuum (e.g., the zero point vibrational energy corrected energy di erence obtained at the B3LYP/6È31G* level of theory is 9.96 kJ mol~1)

Endoscopic treatment of bleeding gastric varices with histoacryl (N-butyl-2-cyanoacrylate): a South European single center experience

BACKGROUND: Endoscopic injection of N-butyl-2-cyanoacrylate is the current recommended treatment for gastric variceal bleeding. Despite the extensive worldwide use, there are still differences related to the technique, safety, and long term-results. We retrospectively evaluated the efficacy and safety of cyanoacrylate in patients with gastric variceal bleeding. PATIENTS AND METHODS: Between January 1998 and January 2010, 97 patients with gastric variceal bleeding underwent endoscopic treatment with a mixture of N-butyl-2-cyanoacrylate and Lipiodol(TM). Ninety-one patients had cirrhosis and 6 had non-cirrhotic portal hypertension. Child-Pugh score at presentation for cirrhotic patients was A-12.1 %; B-53.8 %; C-34.1 % and median MELD score at admission was 13 (3-26). Successful hemostasis, rebleeding rate and complications were reviewed. Median time of follow up was 19 months (0.5-126). RESULTS: A median mixture volume of 1.5 mL (0.6 to 5 mL), in 1 to 8 injections, was used, with immediate hemostasis rate of 95.9 % and early rebleeding rate of 14.4 %. One or more complications occurred in 17.5 % and were associated with the use of Sengstaken-Blakemore tube before cyanoacrylate and very early rebleeding (p < 0.05). Hospital mortality rate during initial bleeding episode was 9.3 %. Very early rebleeding was a strong and independent predictor for in-hospital mortality (p < 0.001). Long-term mortality rate was 58.8 %, in most of the cases secondary to hepatic failure. CONCLUSION: N-butyl-2-cyanoacrylate is a rapid, easy and highly effective modality for immediate hemostasis of gastric variceal bleeding with an acceptable rebleeding rate. Patients with very early rebleeding are at higher risk of death

Aggregation-induced emission of [3]cumulenes functionalized with heptagon-containing polyphenylenes

This is accepted manuscript, the final published article is available in "García Jiménez, V.; et al. Aggregation-induced emission of [3]cumulenes functionalized with heptagon-containing polyphenylenes. Chemical Communications, online (2018). DOI: http://dx.doi.org/10.1039/C8CC00386FWe report the luminiscence at room temperature by aggregate formation of [3]cumulenes functionalized with propeller-like heptagon-containing polyphenylenes. These endgroups turn on the emission of a [3]cumulene by steric protection and restriction of their intramolecular rotations in the aggregates.European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (ERC-2015 -677023).Ministerio de Economía y Competitividad (MINECO, Spain – FEDER) (CTQ2015-70283-P, CTQ2014-53598-R, RyC-2013-12943).Fundação para a Ciência e a tecnologia (Portugal, IF/00759/2013, SFRH/BPD/75782/2011,SFRH/BPD/96707/2013,UID/NAN/50024/2013)

Biocompatible hybrids based on nanographene oxide covalently linked to glycolporphyrins: synthesis, characterization and biological evaluation

The major limitation in the development of hybrids based on graphene oxide (GO) and porphyrins is their dispersibility and stability in aqueous systems due to the hydrophobic character induced by porphyrins. Most of the previous approaches reported the direct functionalization of GO with polyethylene glycol (PEG) chains followed by the self-assembly of porphyrins by π-π interactions. Here, new hybrids were prepared using porphyrins previously functionalized with different number/types of glycol branches to be covalently attached through esterification to the carboxyl groups of GO sheets of nanometric dimensions. The number of the glycol chains and its relative position in the porphyrin core showed to be fundamental to improve the hybrids dispersion and stability in aqueous solutions. The best performing hybrids were characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared, UV-Vis absorption and fluorescence spectroscopy. The in vitro biocompatibility assessment of these hybrids was conducted using human Saos-2 cells. Their effects on cell proliferation and viability, the generation of reactive oxygen species as well as the cell morphology after cell uptake were analysed. The results demonstrate the biocompatibility of these hybrid nanomaterials with human Saos-2 cells, which is very promising for future application in biomedicine namely in cancer therapy.publishe

New triazine bridged triads based on BODIPY-porphyrin systems: extended absorption, efficient energy transfer and upconverted emission

Two novel triads connecting a BODIPY to ethylenediamine substituted porphyrins via triazine linker have been synthesized and characterized. One of the triads is a linear D-A structure with one BODIPY (D) and one porphyrin (A) bridged by the triazine linker and the other one is a branched A-D4 structure with the porphyrin core linked to four BODIPY units. The triads show extended absorption in the visible region with contributions from both porphyrin (Soret band centred at 410–430 nm) and BODIPY units (strong absorption at ≈ 502 nm) in good agreement with the expected molar ratio. Both triads exhibit linear and nonlinear optical properties featuring an efficient energy transfer from the BODIPY donor to the porphyrin acceptor. The nonlinear upconverted emission properties of the triads were studied by two-photon excitation in the Near-infrared (NIR, 710–930 nm). The maximum two-photon absorption cross-section values for the triads (40–70 GM) are larger than those typically reported in this wavelength range for porphyrins and BODIPY. Both the green emission of BODIPY (≈514 nm) and the red emission of porphyrins (650–750 nm) were observed under NIR excitation at 930 nm. The distinct features of triads, namely i) an extended absorption; ii) an efficient energy transfer and iii) the nonlinear upconverted emission featuring a large separation between the excitation and emission wavelengths could be beneficial for application in sensing and imaging procedures.publishe