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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.

Photoreduction of silver salts in the presence of three polyaminocyclodextrin derivatives (AmCD, Figure 1) constitutes a simple and straightforward route to obtain stable Ag nanoparticles. These systems have been suitably characterized (UV-vis, FT-IR, TEM, Figure 2) and tested for their antimicrobial activity.1 We observed that Ag photoreduction is effectively induced by irradiation with green light (513 nm); however, best performances are achieved with the use of a light source having at the same time a significant emission in the near-infrared (NIR) region. On the grounds of analytical and kinetic evidences, we hypothesized a multi-step mechanism for nanoparticle formation. In particular, green irradiation induces an electron-transfer process producing small Ag0 seeds, while the capping agent functions as sacrificial reductant, affording different species (radicals, iminium ions aldehydes). These, in turn, function as reducing agents in a secondary step stimulated by NIR irradiation, from which the final nanocomposite is ultimately obtained.

The chemical synthesis of novel chemotherapeutical leads is evolving thanks to possibility to design molecules with desired physical-chemical and, thus, biological properties. The imidazolium salts, recently proven effective to inhibit bacterial and/or cancer cell growth, posses an amphiphilic nature that is conferred by the imidazolium cation having a polar head generally coupled with aliphatic side chains. Thus, biological properties of imidazolium salts can be tuned through modifications involving the cation structure and/or the anion nature. By covalently linking two imidazolium rings, di-imidazolium salts were obtainedobtain differing in: i) kind of anions; ii) geometric isomerization of di-imidazolium anions; iii) length of the imidazolium alkyl side chains. Preliminarly, eleven di-imidazolium salts, differing for their anionic counterparts, were assayed for: i) antibacterial property, quantified as the minimal concentration inhibiting at least the 90% of bacterial growth (MIC90) using Escherichia coli and Micrococcus luteus as Gram-negative and Gram-positive tester strains; ii) antitumoral activity measured as the concentration inhibiting the 50% of cell growth (IC50) using SKBR-3 breast cancer cell line. All the assayed salts possesses biological activity showing i) 0.1-0.5 and 25-50 µg/ml as MIC90 values against of M. luteus, and E. coli; respectively, and ii) 30-55 µg/ml as IC50 values. Among the tested di-imidazolium salts, three were chosen to further investigate the relationship between biological efficacy and either length of alkyl side chains or imidazolium ring configurations. Geometric isomerization revealed few or no effect while a positive correlation between alkyl chain length and cell-growth inhibitory efficacy was shown. Although further studies have to be performed to elucidate the molecular mechanisms leading to cell growth arrest, this study provide insights on the attractive possibility of di-imidazolium salt exploitation as chemotherapeutical compounds whose activity can be tuned by modifying structural characteristics.

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.

Water contamination is one of the main problems of modern society, and scientific research is continuously involved in identifying solutions able to preserve this valuable source. In this context, we characterized novel ionogels formed by organic salts with different anions. In particular, they show self-strengthening behavior, a quite unusual property for supramolecular gels, and they also exhibit a good load-bearing capacity. These ionogels are able to remove cationic dyes from wastewater. Thanks to their properties, they can be used in different apparatuses like dialysis membranes and as loading in adsorption columns. In the latter case over 95% removal is achieved in less than 10 min. Interestingly, soft materials can be reused for at least 20 cycles, partially regenerated, and reused for further 15 cycles. Comparison with data previously reported in the literature shows that this is a prerogative of this system and this represents not only an improvement but also a warranty of low raw material production after wastewater treatment.