Search

Electrospun systems are becoming promising devices usable for topical treatments. They are eligible to deliver different therapies, from anti-inflammatory to antitumoral. In the current research, polycaprolactone electrospun membranes loaded with synthetic and commercial antitumoral active substances were produced, underlining how the matrix-filler affinity is a crucial parameter for designing drug delivery devices. Nanofibrous membranes loaded with different percentages of Dacarbazine (the drug of choice for melanoma) and a synthetic derivative of Dacarbazine were produced and compared to membranes loaded with AuM1, a highly active Au-complex with low affinity to the matrix. AFM morphologies showed that the surface profile of nanofibers loaded with affine substances is similar to one of the unloaded systems, thanks to the nature of the matrix-filler interaction. FTIR analyses proved the efficacy of the interaction between the amidic group of the Dacarbazine and the polycaprolactone. In AuM1-loaded membranes, because of the weak matrix-filler interaction, the complex is mainly aggregated in nanometric domains on the nanofiber surface, which manifests a nanometric roughness. Consequently, the release profiles follow a Fickian behavior for the Dacarbazine-based systems, whereas a two-step with a highly prominent burst effect was observed for AuM1 systems. The performed antitumoral tests evidence the high-cytotoxic activity of the electrospun systems against melanoma cell lines, proving that the synthetic substances are more active than the commercial dacarbazine.

The synthesis of propargylamines by traditional methods is limited by several drawbacks such as anhydrous conditions, low temperatures and by-products. A3-coupling reactions (aldehydes, amines, and alkynes), that involve a catalytic amount of metal complexes, have been recently recognized as a powerful alternative for the synthesis of these important scaffolds. In this paper, four new silver and gold complexes (3a, 4a, 3b and 4b), bearing N-heterocyclic carbene (NHC) ligands, were tested in A3-coupling reactions, combining the use of harmless metals as catalysts with sustainable reaction conditions (neat conditions or water as solvent). NHC silver(I) and gold(I) complexes were synthesized and characterized by 1H and 13C NMR spectroscopy, ESI-MS and elemental analysis. The molecular structure of the NHC gold(I) complex 4b was determined by single crystal X-ray diffraction. A comparison of the catalytic behavior in A3-coupling reactions among the synthesized complexes disclosed the higher efficiency of gold catalysts. Computational studies shed light on species possibly involved in the catalytic mechanism.

Owing of their accessibility and wide range of reactivities, alkynes make for fascinating building blocks. Either a selective alkyne carbon-carbon triple bond reaction or activation of the terminal alkyne C-H bond may be employed to functionalize them. Monocationic coinage metal complexes with a d10 electronic configuration are effective catalysts for alkyne activation. Silver(I) and gold(I) N-heterocyclic (NHC) systems are emerging as promising catalysts in multicomponent alkyne activation reactions; this review paper focuses on A3 (aldehyde-amine-alkyne)-coupling reaction and carbon dioxide fixation, furnishing a systematic overview of the scientific advances achieved during the last two decades. This study will carefully compare the corresponding silver and gold complexes employed in the two processes. The differences in reaction routes brought about by the catalyst ligand structure will be investigated with an emphasis on evaluating the benefits provided by the easily tuneable NHC backbone, in terms of chemo- and stereo-selectivity.

In recent years, the number of people suffering from cancer has risen rapidly and the World Health Organization and U.S. and European governments have identified this pathology as a priority issue. It is known that most bioactive anticancer molecules do not target a single protein but exert pleiotropic effects, simultaneously affecting multiple pathways. In our study, we designed and synthesized a new series of silver N-heterocyclic carbene (NHC) complexes [(NHC)

Until the year 2000, gold compounds were considered catalytically inert. Subsequently, it was found that they are able to promote the nucleophilic attack on unsaturated substrates by forming an Au–π-system. The main limitation in the use of these catalytic systems is the ease with which they decompose, which is avoided by stabilization with an ancillary ligand. N-heterocyclic carbenes (NHCs), having interesting σ-donor capacities, are able to stabilize the gold complexes (Au (I/III) NHC), favoring the exploration of their catalytic activity. This review reports the state of the art (years 2007–2022) in the nucleophilic addition of amines (hydroamination) and water (hydration) to the terminal and internal alkynes catalyzed by N-heterocyclic carbene gold (I/III) complexes. These reactions are particularly interesting both because they are environmentally sustainable and because they lead to the production of important intermediates in the chemical and pharmaceutical industry. In fact, they have an atom economy of 100%, and lead to the formation of imines and enamines, as well as the formation of ketones and enols, all important scaffolds in the synthesis of bioactive molecules, drugs, heterocycles, polymers, and bulk and fine chemicals.

In this paper is reported the synthesis of N,N′ hydroxy derivative of NHC silver (3a–4a) and gold(I) (3b–4b) complexes of general formula [M(NHC)2]+ [MX2]−. All compounds were characterized by spectroscopic and analytic techniques. The complexes turned out to be effective in both catalytic and biological applications. They catalyzed the coupling of aldehyde, piperidine, and phenylacetylene in A3-reaction to produce propargylamines and showed antimicrobial activity. In fact, minimal inhibition concentration (MIC) tests with Gram-positive and Gram-negative bacteria demonstrated that the silver compounds are selective toward E. coli, whereas the gold analogues are active against S. aureus. Moreover, the N,N′ hydroxy derivative of NHC silver complexes 3a and 4a exhibited good anticancer activity on the HeLA cancer cells (3a-IC50 = 12.2 ± 0.1 µM, 4a-IC50 = 11.9 ± 1.2 µM), whereas gold complex 4b displayed good anticancer activity towards the MCF-7 cells (IC50 = 12.2 ± 1.2 µM).

Herein, we report the synthesis and the multiple anti-tumor properties of new gold and silver carbene complexes. The chemical modifications, grounded on our previous studies, led us to identify a good lead complex, gold-based, whose biological features are very exciting and promising in the anti-cancer research and could be further developed. Indeed, the bis-[4,5-dichloro-(N-methyl-N&rsquo, (2-hydroxy-2-phenyl)ethyl-imidazole-2-ylidene)gold(I)]+[dichloro-gold]&minus, (AuL7) complex possesses the ability to interfere with at least three important and different intracellular targets, namely the human topoisomerases I and II and tubulin, which are able to modulate metabolic processes not directly correlated each other. We proved that the modifications of the ligands structure in AuL7, with respect to another already published complex, i.e., bis-[4,5-dichloro-(N-methyl-N&rsquo, (cyclopentane-2ol)-imidazole-2-ylidine)gold(I)]+[dichloro-gold]&minus, (AuL4), produce a different behavior toward tubulin-polymerization process, since AuL7 is a tubulin-polymerization inhibitor and AuL4 a stabilizer, with the final same result of hampering the tumor growth. Taken together, our outcomes designate AuL7 as a promising compound for the development of multi-targeted anti-cancer therapies.

Copolymerization of styrene (S) with p-methylstyrene (PMS) and p-chlorostyrene (PCS), catalyzed by half-titanocenes (CpCH2CH2O)TiCl2 (1) and (CpCH2CH2OCH3)TiCl3 (2) activated by methylaluminoxane (...

Silver and gold complexes bearing unsaturated N-heterocyclic carbene ligands, with unsymmetrical N-substituents and hydrogen or chlorine on backbone, have been synthetized and their efficiency tested in A3-coupling (aldehyde–alkyne–amine) reactions. Gold complexes showed higher activity than corresponding silver ones, even if the significant role of the backbone substituents should not be neglected. Indeed, complexes with chlorine substituted backbone were more efficient than hydrogen analogous. According to DFT calculations, electronic differences among complexes are able rationalize the different catalytic behavior, whereas steric properties play a minor part.

Hoveyda-Grubbs 2nd generation catalyst that has the alkylidene functionalized with pyrene (HG2pyrene) was synthesized and characterized. This catalyst can be bound to carbonaceous filler (graphite, graphene or carbon nanotubes) by &pi, stacking interaction, but, since the catalytic site become poorly accessible to the incoming monomer, its activity in the ROMP (Ring Opening Metathesis Polymerization) is reduced. This is due to the fact that the above interaction also occurs with the aryl groups of NHC ligand of the ruthenium, as demonstrated by nuclear magnetic resonance and by fluorescence analysis of a solution of the catalyst with a molecule that simulated the structure of graphene. Very interesting results were obtained using HG2pyrene as a catalyst in the ROMP of 2-norbornene and 1,5-cyclooctadiene. The activity of this catalyst was the same as that obtained with the classical commercial HG2. Obviously, the polymers obtained with catalyst HG2pyrene have a pyrene as a chain end group. This group can give a strong &pi, stacking interaction with carbonaceous filler, producing a material that is able to promote the dispersion of other materials such as graphite in the polymer matrix.