Enhancement of two-photon absorption cross-section and singlet-oxygen generation in porphyrins upon beta-functionalization with donor-acceptor substituents

The microwave-enhanced synthesis, comparative singlet oxygen sensitization efficiency, and nonlinear optical characterization of a new beta-functionalized porphyrin and its copper complex are described. We show that the introduction of a donor-acceptor push-pull conjugated fragment in the beta position strongly perturbs the porphyrin electronic structure leading to a remarkable one- and two-photon NIR absorption enhancement.     

Enantioselective Organocatalytic Reduction of β‐Trifluoromethyl Nitroalkenes: An Efficient Strategy for the Synthesis of Chiral β‐Trifluoromethyl Amines

An efficient organocatalytic stereoselective reduction of β‐trifluoromethyl‐substituted nitroalkenes, mediated by 3,5‐dicarboxylic ester‐dihydropyridines (Hantzsch ester type), has been successfully developed. A multifunctional thiourea‐based (S)‐valine derivative was found to be the catalyst of choice, promoting the reaction in up to 97 % ee. The methodology has been applied to a wide variety of substrates, leading to the formation of differently substituted precursors of enantiomerically enriched β‐trifluoromethyl amines. The mechanism of the reaction and the mode of action of the metal‐free catalytic species were computationally investigated; on the basis of DFT transition‐state (TS) analysis, a model of stereoselection was also proposed.     

Crystal structure of the complex between 7,7,8,8-tetracyanoquinodimethane and 1-oxide-2-phenyl-quinoline

A series of complexes between 1-oxide quinolines and 7,7,8,8-tetracyanoquinodimethane has been synthesized and one of them has been analyzed by x-ray diffraction methods. Crystals of the title compound are monoclinic (C₁₅H₁₁NO·C₁₂H₄N₄), space groupP2₁/n,a=44.525(4),b=7.326(2),c=6.531(2) Å,=90.23(3)°. The structure was solved by direct methods and refined by block-matrix least-squares to giveR=0.047 for 1865 reflections above 2(I). Molecular dimensions, interplanar distances, empirical method and IR spectra suggest a -^* interaction with very low charge-transfer in the complex.     

Monitoring the synthetic procedures of commercial drugs by 2H NMR spectroscopy: the case of ibuprofen and naproxen

We determined the D/H isotope ratios of some ibuprofen and naproxen samples by (2)H NMR spectroscopy. Some of these values were found to be useful for collecting hints on the synthetic procedures employed to prepare these drugs. Site-specific isotope ratio analysis shows great potentials in the fight against patent infringement.     

Do computed crystal structures of nonpolar molecules depend on the electrostatic interactions? The case of tetracene

We present a strategy for comparing the global properties of competing potential models. By systematically sampling the potential energy surface of crystalline tetracene, we assess how the number, energy and structure of its minima are modified by switching on (or off) the Coulombic interactions. The increased complexity of the Coulombic potential leads to a more "rugged" potential energy surface with a larger number of minima, but the effect is not large. In fact, we find a subset of minima stable only in presence of the Coulombic interactions, a smaller subset stable only in their absence, and a large majority stable in both cases. Among these, there is a very good, but not perfect, correlation between the energies and the structures computed with and without the electrostatic interactions. Although electrostatic interactions play a role even in a rigid nonpolar molecule such as tetracene, they are not as crucial as often believed, because altering the electrostatic model (or switching it off completely) leads, in most cases, to equivalent results.     

Assessment of water-soluble pi-extended squaraines as one- and two-photon singlet oxygen photosensitizers: design, synthesis, and characterization

Singlet oxygen sensitization by organic molecules is a topic of major interest in the development of both efficient photodynamic therapy (PDT) and aerobic oxidations under complete green chemistry conditions. We report on the design, synthesis, biology, and complete spectroscopic characterization (vis-NIR linear and two-photon absorption spectroscopy, singlet oxygen generation efficiencies for both one- and two-photon excitation, electrochemistry, intrinsic dark toxicity, cellular uptake, and subcellular localization) of three classes of innovative singlet oxygen sensitizers pertaining to the family of symmetric squaraine derivatives originating from pi-excessive heterocycles. The main advantage of pi-extended squaraine photosensitizers over the large number of other known photosensitizers is their exceedingly strong two-photon absorption enabling, together with sizable singlet oxygen sensitization capabilities, for their use at the clinical application relevant wavelength of 806 nm. We finally show encouraging results about the dark toxicity and cellular uptake capabilities of water-soluble squaraine photosensitizers, opening the way for clinical small animal PDT trials.     

Determination of alpha-amylase inhibitor activity of phaseolamin from kidney bean (Phaseolus vulgaris) in dietary supplements by HPAEC-PAD

Some dietary supplements, so-called 'starch-blockers', used to control overweight, are based on the protein concentrate of the kidney bean, known to contain high levels of the alpha-amylase inhibitor phaseolamin, which may hinder the digestion of complex carbohydrates, thereby promoting or supporting weight loss. Currently, methods to determine the levels of alpha-amylase inhibitor are based on the measurement of alpha-amylase activity using colorimetric methods that cannot be applied to dietary supplements because they are complex mixtures of different ingredients that may interfere with the measurement. The aim of this study was to develop an alternative method to determine the level of phaseolamin in dietary supplements, using high-performance anion-exchange chromatography coupled with pulsed amperometric detection (HPAEC-PAD) to measure the amount of maltose resulting from the action of the enzyme porcine alpha-amylase on soluble starch in the presence and absence of the inhibitor. The assay described proved sensitive and accurate for use with both dietary supplements and raw materials.