Fullerene Derivatives Embedded in Hybrid Sol-Gel Glasses: Nonlinear Optical Properties and Optical Limiting Performances

Hybrid organic-inorganic materials are investigated as suitable materials for inclusion of fullerene derivatives and for fabrication of laser protection devices. A specific synthesis has been developed in order to optimize non-linear optical performances of fullerene derivatives. 3-glicydoxypropyltrymethoxysilane has been used as an inorganic and organic network former to obtain the host material. The sol-gel synthesis consists of the hydrolysis and condensation in acidic conditions of the inorganic network. Epoxy polymerization has been achieved by using zirconium or BF₃ alkoxides precursors. Bulk and multilayer materials doped with a fullerene derivative have been fabricated. They show good optical requirements: high fullerenes concentration, high microstructural homogeneity, high laser damage threshold and high optical limiting efficiency. Optical limiting (OL) mechanisms have been investigated. The most effective in the sol-gel materials is the reverse saturable absorption (RSA) one. However, different mechanisms, like non-linear (NL) scattering and NL refraction contribute to a different extent. Open- and closed-aperture OL and z-scan measurements on sol-gel samples show the contribution of NL scattering and NL refraction at 690 nm. Laser damage threshold has been characterized as a function of the structure of the samples and of the optical configurations (f/66 and f/5).     

An alternative quinoline synthesis by via Friedländer reaction catalyzed by Yb(OTf)3

Quinolines have been synthesized in very good yields from 2-aminoarylketones and differently substituted carbonyl compounds in the presence of Yb(OTf)₃ as the catalyst. The method is applicable to both cyclic and acyclic carbonyl compounds with only slight differences in the experimental procedure.     

Ion pair recognition of quaternary ammonium and iminium salts by uranyl-salophen compounds in solution and in the solid state

Efficient ditopic receptors for quaternary ammonium and iminium salts have been obtained upon functionalization of the uranyl-salophen unit with conformationally flexible side arms bearing phenyl or beta-naphthyl substituents. Binding affinities in chloroform solution have been measured for a large number of quaternary salts comprising tetramethylammonium (TMA), tetrabutylammonium (TBA), acetylcholine (ACh), N-methylpyridinium (NMP), and N-methylisoquinolinium (NmiQ) cations. Recognition of the anion partner is ensured by coordination to the hard Lewis acidic uranyl center, whereas cation-pi/CH-pi interactions of the quaternary ions are established with the aromatic pendants. The role of the cation-anion interactions on the dynamics of exchange between the free and complexed species is discussed. Solid-state structures have been obtained for a few salt-receptor combinations. In the solid state, side-armed receptor molecules form assemblies that enclose ion pair aggregates of varying composition and structure, including AChCl dimers, two different kinds of tetrameric (TMA)Cl clusters, and unidimentional salt strips of (NMP)Br. The lack of side arms as preferential binding sites for the polar quaternary cations prevents association patterns of the kinds formed with the side-armed receptors, as shown by the crystal structure of the complex of (TMA)Cl with the parent uranyl-salophen receptor.     

Structure and stereochemistry of a new cytotoxic polychlorinated sulfolipid from Adriatic shellfish

A detailed analysis of the causative toxins contained in the hepatopancreas of toxic mussels from the northern Adriatic sea has been carried out. Along with some DSP (diarrhetic shellfish poisoning) type toxins, such as okadaic acid, yessotoxin, and their derivatives, which are involved in a number of human intoxications throughout the world, we have now isolated a new cytotoxin, a polychlorinated sulfolipid 1, whose gross structure has been elucidated by spectral analysis, including various 2D NMR techniques. The relative stereochemistry of 1 was elucidated by successful application of the J-based configuration analysis developed for acyclic compounds using carbon-proton spin-coupling constants ((2,3)J(C,H)) and proton-proton spin-coupling constants ((3)J(H,H)); its absolute stereochemistry was established by the Mosher method. Compound 1 possesses in vitro cytotoxicity against WEHI 164 and RAW 264.7 cells.     

Surface-controlled spatially heterogeneous physical properties of a supramolecular gel with homogeneous chemical composition

Controlling supramolecular self-assembly across multiple length scales to prepare gels with localised properties is challenging. Most strategies concentrate on fabricating gels with heterogeneous components, where localised properties are generated by the stimuli-responsive component. Here, as an alternative approach, we use a spiropyran-modified surface that can be patterned with light. We show that light-induced differences in surface chemistry can direct the bulk assembly of a low molecular weight gelator, 2-NapAV, meaning that mechanical gel properties can be controlled by the surface on which the gel is grown. Using grazing incidence X-ray diffraction and grazing incidence small angle X-ray scattering, we demonstrate that the origin of the different gel properties relates to differences in the architectures of the gels. This provides a new method to prepare a single domain (i.e., chemically homogeneous) hydrogel with locally controlled (i.e., mechanically heterogeneous) properties.

A mechanical pattern is created in a hydrogel film by pre-patterning the underlying surface chemistry. This allows spatial variation of the viscous component of the gel, controlling dissipative forces in the gel film without altering gel chemistry.     

Urinary Metabolomics Study of Patients with Bicuspid Aortic Valve Disease

Bicuspid aortic valve (BAV) is the most common congenital heart defect responsible for valvular and aortic complications in affected patients. Causes and mechanisms of this pathology are still elusive and thus the lack of early detection biomarkers leads to challenges in its diagnosis and prevention of associated cardiovascular anomalies. The aim of this study was to explore the potential use of urine Nuclear Magnetic Resonance (NMR) metabolomics to evaluate a molecular fingerprint of BAV. Both multivariate and univariate statistical analyses were performed to compare the urinary metabolome of 20 patients with BAV with that of 24 matched controls. Orthogonal partial least squared discriminant analysis (OPLS-DA) showed statistically significant discrimination between cases and controls, suggesting seven metabolites (3-hydroxybutyrate, alanine, betaine, creatine, glycine, hippurate, and taurine) as potential biomarkers. Among these, glycine, hippurate and taurine individually displayed medium sensitivity and specificity by receiver operating characteristic (ROC) analysis. Pathway analysis indicated two metabolic pathways likely perturbed in BAV subjects. Possible contributions of gut microbiota activity and energy imbalance are also discussed. These results constitute encouraging preliminary findings in favor of the use of urine-based metabolomics for early diagnosis of BAV.     

A simple model for the structure of fractal aggregates

Structural properties of small aggregates containing up to 100 particles have been studied through detailed Monte Carlo cluster-cluster aggregation simulations in both diffusion-limited and reaction-limited conditions. First, the radius of gyration, the radius of the smallest sphere encompassing the cluster, and the particle-particle correlation function, g(r), have been computed based on the positions of all the particles in the cluster, and their fractal scaling has been analyzed. Then, an empirical model has been developed to simulate the g(r) function for aggregates of any size and used to determine the corresponding structural properties and scattering structure factors. Finally, in order to illustrate the application of the structural properties thus computed, two experiments on diffusion-limited aggregation have been performed, and the average scattering structure factors have been measured as a function of time using a small-angle light-scattering device. The obtained average scattering structure factors have been simulated using the Smoluchowski population balance equations, using the single aggregate structural properties and scattering structure factor predicted by the developed empirical g(r) model.     

α-Oxohydrazones as imine component in the synthesis of 4-functionalized azetidinones by the Staudinger reaction

1-(Methyl-p-tolyl-amino)-3-phenoxy-2-azetidinones 4-COX and 4-R substituted (COX: X=Me, Et, Ph, NMe₂, NEt₂, OBu^t; R=Me, Et, Ph) were smoothly prepared from the corresponding α-(methyl-p-tolyl)hydrazonylated ketones, amides and esters via [2+2] cycloaddition with phenoxyketene. The reaction was generally high-yielding and diastereoselective, leading to β-lactams with a cis relationship between the PhO and the COX moieties, except for R=Ph, where an opposite stereoselectivity was instead observed. The azetidinones represent interesting intermediates which couple protection at N(1) and functionalization at position 4 of the ring. Deprotection of N(1) can be easily attained by oxidative N-N cleavage with magnesium monoperoxyphthalate.     

Uranyl-salophen based ditopic receptors for the recognition of quaternary ammonium halides

Uranyl-salophen complexes endowed with aromatic side arms behave as very efficient ditopic receptors towards tetralkylammonium halides as a result of a combination of Lewis acid-base and cation-pi interactions.