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In order to obtain useful insights on the mechanism of formation of 2(3H)-imino-1,3,4-thiadiazoles by oxidative cyclization of aldehyde thiosemicarbazones with Cu(II) or Fe(III) salts, a competitive reactivity study was performed on a suitable set of diversely substituted substrates, by means of HPLC techniques. This approach enabled to exploit Hammett's equation without performing otherwise difficult-to-run kinetic experiments. The results presented herein support the hypothesis that the formation of the thiadiazole ring is induced by the attack of the oxidizing Lewis acid metal cation onto the imine-like nitrogen atom of the thiosemicarbazone substrate. Beyond mechanistic interpretation, the paper particularly focuses onto the methodological issues implied. [ABSTRACT FROM AUTHOR]

Abstract: Several anti-6-substituted 1,3-dioxepan-5-ols were kinetically resolved using an immobilized lipase (Amano PS–C II) in toluene in the presence of vinyl acetate at 30°C. This approach provided, in some cases, the alcohol and the acetate in high enantiomeric purity, depending on the nature of the substituent (R=N3, SePh, I, OBn) and the acetal group (unsubstituted or dimethyl). The role of the size of substituents is also discussed. Enantiopure anti-6-substituted 1,3-dioxepan-5-ols are useful building blocks. [Copyright &y& Elsevier]

Abstract: Eleven β-hydroxy selenides were kinetically resolved using an immobilized lipase (Amano PS-C II) in toluene in the presence of vinyl acetate at 30°C. This approach provided, in several cases, both enantiomers in high enantiomeric excess. The role of the size of substituents and the behaviour of cyclic β-hydroxy selenides is also discussed. Enantiopure β-hydroxy selenides are useful building blocks. As an application of this chemistry, enantiopure (1S,2R)-indene oxide was obtained in one step from the proper enantiopure β-hydroxy selenide. [Copyright &y& Elsevier]

The thermodynamics of binding between native α- and β-cyclodextrin towards several p-nitro-aniline derivatives was examined, in order to gain further insights about the occurrence of different interaction modes for the two hosts. Valuable information was achieved regarding the ‘expanded hydrophobic sphere’ of α-cyclodextrin. Furthermore, very interesting and unexpected aspects of the behavior of β-cyclodextrin were enlightened, such as the crucial role played by hydrogen bond interactions. Experimental data were examined under the perspective of the ‘enthalpy–entropy compensation effect’, and some ideas about this topic are discussed. [Copyright &y& Elsevier]

Some composite materials have been prepared, constituted by a cyclodextrin-bis-urethane-based nanosponge matrix in which a reduced graphene oxide/silver nanoparticles photocatalyst has been dispersed. Different chain extenders were employed for designing the nanosponge supports, in such a way as to decorate their hyper-cross-linked structure with diverse functionalities. Moreover, two different strategies were explored to accomplish the silver loading. The obtained systems were successfully tested as catalysts for the photodegradation of emerging pollutants such as model dyes and drugs. Enhancement of the photoactive species performance (up to nine times), due to the synergistic local concentration effect exerted by the nanosponge, could be assessed. Overall, the best performances were shown by polyamine-decorated materials, which were able to promote the degradation of some particularly resistant drugs. Some methodological issues pertaining to data collection are also addressed. [ABSTRACT FROM AUTHOR]

Needing to extend the shelf-life of packaged food and the evolving consumer demands led researchers to seek innovative, eco-friendly, and biocompatible packaging solutions. Starch is among the most promising natural and renewable alternatives to non-degradable plastics. Here, we deeply study the structural features of starch films modified by adding citric acid (CA) or sodium citrate (SC) as a cross-linker and polyethylene glycol 200 (PEG200) as a plasticizer and obtained through solvent casting. The substances' influence on starch films was evaluated through Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR) and Solid-state Nuclear Magnetic Resonance (ss-NMR) spectroscopies. Films' macroscopic properties, such as swelling index, solubility, thermo-mechanical features, and moisture absorption, were also assessed to foresee potential applications. Proper amounts of CA, CS, and PEG200 improve film properties and inhibit starch chains' retrogradation and recrystallization. Besides, the chemical neighbourhood of nuclei observed through ss-NMR significantly changed alongside the polymer chains' mobility. The latter result indicates a different polymer chain structural organization that could justify the film's higher resistance to thermal degradation and elongation at the break. This methodological approach is effective in predicting the macroscopic behaviour of a polymeric material and could be helpful for the application of such products in food preservation. Starch-based films incorporating cross-linkers and plasticizers were obtained by solvent-casting of aqueous dispersions and examined to determine various micro and macroscopic features. Cross-linkers and plasticizers impart distinctive microscopic characteristics to the films, enabling a correlation and explanation of their different macroscopic properties. [Display omitted] [ABSTRACT FROM AUTHOR]

In the last years, the development of nano-formulations for cancer treatment represents one of the major challenges of the scientific research. The prodrug strategy, that combines chemotherapeutic agents with nanocarriers such as halloysite nanotubes (HNTs), is a promising strategy both to improve the biological activity of the drug molecules and to reduce the side effects of drugs. Herein we report the synthesis and characterization of a HNTs prodrug based on 1,2,3-triazole units covalently linked to HNTs external surface, bearing different positively charged moieties, which could present interesting pharmacological activities. [ABSTRACT FROM AUTHOR]

The stability and stoichiometric ratio of binary complexes among five fluorophores and β-cyclodextrin (β-CD) or heptakis-(6-amino-6-deoxy)-β-cyclodextrin (am-β-CD) were determined by means of fluorescence measurements in borate buffer at pH=8.0 and 9.0. Structure of both host and guest affected the characteristics of the binary complexes. Pyrene and anthraquinone formed a 1:2 (fluorophore: cyclodextrin) complex with both cyclodextrins. Xanthone formed 1:1 complex with β-CD and 1:2 complex with am-β-CD. A more defined behaviour was observed for crysene. In fact, both stoichiometric different complexes were detected with both hosts. Only 1:1 complexes were observed for antracene. The complex stability was affected by the pH of the solution. MM2 calculations were performed in order to gain information about the forces working on the formation of complexes. [Copyright &y& Elsevier]

Nowadays, water pollution represents a serious problem both for agriculture and human health. Find innovative strategy for a large-scale removal of pollutants from wastewaters is thus a challenge. In this context, both cyclodextrin derivatives and clay minerals have been used as low-cost nanomaterials for the sorption of pollutants because of their features. Cyclodextrin derivatives are particularly recognized for the removal of organic chemicals, drugs, and pesticides from wastewater. Hectorite (Ht), a clay mineral of smectite group, shows high cation exchange capacity and negatively charged basal surfaces that could allow the removal both of heavy metal ions and organic pollutants. Herein, the synthesis of a hybrid organic/inorganic nanomaterial based on the chemical modification of Ht by grafting modified β-cyclodextrin units is reported. In this way systems with complementary and synergistic adsorption ability for removal of both organic pollutants and heavy metal ions were developed. Two different synthetic approaches were investigated, and the obtained nanomaterials were subjected to thorough structural characterization by FT-IR and 13C solid state NMR spectroscopies, dynamic light scattering, and ζ-potential measurements and the loading of organic moieties was verified by thermogravimetric analysis. In addition, the morphology was investigated by high angle annular dark field transmission electron microscopy (HAADF/STEM) coupled with energy dispersive X-ray spectroscopy (EDX). The synthetized nanomaterial was tested as a sorbent for the removal of antibiotics, organic dyes and heavy metal ions. Finally, the simultaneous filtration of ciprofloxacin and Pb(II) ions, chosen as models, from simulated wastewater by a column filtration laboratory prototype was investigated, too. [Display omitted] • The synthesis of organic/inorganic nanomaterial based on hectorite and β-cyclodextrin is reported. • The nanomaterial was tested as a sorbent for the removal of different pollutant • Thanks to cyclodextrins the nanomaterial showed better adsorption performance than hectorite • Recycling tests showed that the nanomaterial can be reused for at least 4 cycles. • A laboratory column filtration system was set up to simultaneously remove different pollutants [ABSTRACT FROM AUTHOR]

Four mixed cyclodextrin-calixarene nanosponges were tested as possible Drug Delivery Systems, using Tetracycline antibiotic as a suitable model drug. The selected nanosponges featured a different composition ratio between the two host co-monomer components, and the possible presence of ionisable amine or carboxyl groups deriving from chemical post-modification. The pH-dependent absorption and release abilities of the materials were verified; in particular release kinetics showed the occurrence of a simple first-order profile. The antibacterial activity of nanosponge-tetracycline composites suitably prepared under sterile conditions was assayed towards both Gram-positive and Gram-negative typical bacterial strains, showing in some cases an interesting improvement of the biocidal activity. [ABSTRACT FROM AUTHOR]

Silver nanoparticles stabilized by means of poly -(6- N , N -dimethyl-propylenediamino)-(6-deoxy)-β-cyclodextrin were synthesized, characterized by different techniques (UV–vis spectroscopy, Dynamic Light Scattering, High Resolution Transmission Electron Microscopy, Fourier-transform IR Spectroscopy) and used as catalysts for the reduction of various nitrobenzene derivatives with sodium borohydride. The nanocomposites obtained appear to have an organized structure, with a metal core surrounded by a layer-structured coating shell. Kinetic data, rationalized in terms of a modified Langmuir–Hinshelwood model, evidenced a non-linear dependence of the reaction rate on the concentration of the catalyst. This was explained on the grounds of the catalytic activity of differently covered catalyst areas. Careful analysis of kinetic data, in particular the effect of the para substituent on the nitroarene structure and the trends of the induction period observed at the beginning of the reaction, provided with interesting insights on the reaction course, and brought us to critically reconsider several mechanistic ideas reported in previous literature. [ABSTRACT FROM AUTHOR]