Annaluisa Mariconda

Effect of incorporation of POSS compounds and phosphorous hardeners on thermal and fire resistance of nanofilled aeronautic resins

The aim of this work is the identification of the best strategy for improving thermal, fire resistance and electrical conductivity of an epoxy resin for aeronautic applications. The effect of DodecaPhenyl POSS (DPHPOSS), Epoxycyclohexyl POSS (ECPOSS), Glycidyl POSS (GPOSS) and TriglycidylCyclohexyl POSS (TCPOSS) to act as flame retardants of the resin was evaluated. Flame retardancy tested by the limiting oxygen index (LOI) indicated that GPOSS has meaningful effects on the flame retardancy of the epoxy mixture. The incorporation of 5 wt% of GPOSS into the epoxy matrix resulted in a LOI value of 33 with respect to 27 of the pure epoxy mixture. The trend observed by LOI tests was confirmed by mass loss calorimetry measurements: a decrease from 540 kW m−2 down to 327 kW m−2 was observed in the peak of heat release rate (PHRR). LOI and PHRR values were compared with those obtained for the same resin replacing the 4,4′-diaminodiphenyl sulfone (DDS) with the bis(3-aminophenyl) phenylphosphineoxide (BAPPO) and the bis(3-aminophenyl) methyl phosphine oxide (BAMPO). BAMPO and BAPPO proved to be more effective than POSS compounds to increase LOI values. Carbon nanotubes (CNTs), embedded inside the epoxy resin to enhance electrical conductivity, are found to affect significantly fire properties of epoxy systems mainly by preventing the epoxy systems from forming intumescent charring.

The Pivotal Role of Symmetry in the Ruthenium-Catalyzed Ring-Closing Metathesis of Olefins

The synthesis of Ru-based precatalysts with N-heterocyclic carbene (NHC) ligands bearing syn- and anti-methyl groups on the NHC backbone and aryl N-substituents with differing steric bulk was carried out. The catalytic behavior of the monophospine Ru precatalysts (7a, 7b, 8a, and 8b) was compared to the corresponding family of phosphine-free catalysts (9a, 9b, 10a and 10b) in the ring-closing metathesis (RCM) of olefins. These catalysts showed high efficiency in RCM reactions and the syn-isomers 7a and 9a, in particular, proved to be among the most active catalysts in the formation of tetrasubstituted olefins through RCM. DFT studies on the entire RCM catalytic cycle of hindered olefins were performed to rationalize the different behaviors of catalysts with syn- and anti-methyl groups on the NHC backbone. Theoretical results not only disclosed how NHC symmetry influences the overall activity of the catalyst, but also gave relevant and more general indications on the crucial steps of the RCM of olefins.

Healing efficiency and dynamic mechanical properties of self-healing epoxy systems

Several systems to develop self-repairing epoxy resins have recently been formulated. In this paper the effect of matrix nature and curing cycle on the healing efficiency and dynamic mechanical properties of self-healing epoxy resins were investigated. We discuss several aspects by transferring self-healing systems from the laboratory scale to real applications in the aeronautic field, such as the possibility to choose systems with increased glass transition temperature, high storage modulus and high values in the healing functionality under real working conditions.

Healing agent for the activation of self-healing function at low temperature

The development of smart composites capable of self-repair in aeronautical structures is still at the planning stage owing to complex issues to overcome. It is critical that self-healing activity functions at low working temperatures which can reach values as low as −50 °C. Also, another problem concerns the components’ stability of the proposed composites which are compromised at the cure temperatures necessary for good performance of the composite. Here, we show a multifunctional autonomically healing composite with self-healing function capable at very low temperatures (−50 °C). The self-repair function in this self-healing system is based on the metathesis polymerization of 5-ethylidene-2-norbornene/dicyclopentadiene (ENB/DCPD) blend activated by Hoveyda-Grubbs’1st generation (HG1) catalyst, dispersed at molecular level in the matrix. The formulated material shows a self-healing efficiency of about 72%.

Synthesis, characterization and catalytic behaviour of a palladium complex bearing a hydroxy-functionalized N-heterocyclic carbene ligand

The synthesis of a new stable palladium(II) complex (3) featuring an unsymmetrical substituted N-heterocyclic carbene (NHC) ligand with a pendant hydroxy-functionalized group was successfully accomplished via transmetalation of the corresponding bis-NHC silver(I) complex (2). Solid-state structures of both 2 and 3 were determined by single-crystal X-ray diffraction. The catalytic behaviour of 3 in the direct regioselective arylation of furan and thiophene derivatives by using challenging aryl halides was studied, revealing that 3 was capable of promoting these environmentally attractive coupling reactions to afford arylated heterocycles in moderate to good yields.

Synthesis and Antitumor Activity of New Group 3 Metallocene Complexes

The quest for alternative drugs with respect to the well-known cis-platin and its derivatives, which are still used in more than 50% of the treatment regimens for patients suffering from cancer, is highly needed. In this context, organometallic compounds, which are defined as metal complexes containing at least one direct covalent metal-carbon bond, have recently been found to be promising anticancer drug candidates. A series of new metallocene complexes with scandium, yttrium, and neodymium have been prepared and characterized. Some of these compounds show a very interesting anti-proliferative activity in triple negative breast cancer cell line (MDA.MB231) and the non-hormone sensitive prostate cancer cell line (DU145). Moreover, the interaction of some of them with biological membranes, evaluated using liposomes as bio-membrane mimetic model systems, seems to be relevant. The biological activity of these compounds, particularly those based on yttrium, already effective at low concentrations on both cancer cell lines, should be taken into account with regard to new therapeutic approaches in anticancer therapy.

Novel Gold and Silver Carbene Complexes Exert Antitumor Effects Triggering the Reactive Oxygen Species Dependent Intrinsic Apoptotic Pathway

Cisplatin and other platinum‐based drugs are well‐known valid anticancer drugs. However, during chemotherapy, the presence of numerous side effects and the onset of frequent phenomena of resistance has pushed many research groups to devise new metal‐based compounds holding improved anticancer properties and fewer undesired effects. Amongst the variety of synthesized compounds, significant antiproliferative effects have been obtained by employing organometallic compounds, particularly those based on silver and gold. With this in mind, we synthesized four compounds, two silver complexes and two gold complexes, with good inhibitory effects on the in vitro proliferation of breast and ovarian cancer‐cell models. The antitumor activity of the most active compound, that is, AuL4, was found to be ninefold higher than that of cisplatin, and this compound induced dramatic morphological changes in HeLa cells. AuL4 induced PARP‐1 cleavage, caspases 3/7 and 9 activation, mitochondria disruption, cytochrome c release in cancer‐cell cytoplasm, and the intracellular production of reactive oxygen species. Thus, AuL4 treatment caused cancer‐cell death by the intrinsic apoptotic pathway, whereas no cytotoxic effects were recorded upon treating non‐tumor cell lines. The reported outcomes may be an important contribution to the expanding knowledge of medicinal bio‐organometallic chemistry and enlarge the available anticancer toolbox, offering improved features, such as higher activity and/or selectivity, and opening the way to new discoveries and applications.

FT‐IR Investigation of Hoveyda‐Grubbs’2nd Generation Catalyst in Self‐Healing Epoxy Mixtures

The development of smart composites capable of self‐repair on aeronautical structures is still at the planning stage owing to complex issues to overcome. A very important issue to solve concerns the components’ stability of the proposed composites which are compromised at the cure temperatures necessary for good performance of the composite. In this work we analyzed the possibility to apply Hoveyda Grubbs’ second generation catalyst (HG2) to develop self‐healing systems. Our experimental results have shown critical issues in the use of epoxy precursors in conjunction with Hoveyda‐Grubbs II metathesis catalyst. However, an appropriate curing cycle of the self‐healing mixture permits to overcome the critical issues making possible high temperatures for the curing process without deactivating self‐repair activity.

Inhibition of human Topoisomerase II by new N,N,N-trimethylethanammonium iodide alkylcarbazole derivatives

Chemotherapy is used for the treatment of all stages of breast cancer, including the metastatic stage of the disease. Treatment regimens are generally tailored for each patient′s particular situation. However, chemotherapeutic agents are the leading cause of serious drug‐related adverse effects; moreover, drug resistance often occurs. In this study, we designed and synthesized a new series of N‐alkylcarbazoles derived from ellipticine, an alkaloid with a carbazole skeleton initially used in the treatment of metastatic breast cancer and later dismissed because of poor aqueous solubility and severe side effects. After evaluating the binding modes of our class of newly synthesized compounds with human topoisomerase II (hTopo II), we performed hTopo II decatenation assays, identifying compound 4 f (2‐(4‐((3‐chloro‐9H‐carbazol‐9‐yl)pentyl)piperazin‐1‐yl)‐N,N,N‐trimethylethanammonium iodide) as a good inhibitor. Moreover, 4 f and 4 g (2‐(4‐((3‐chloro‐9H‐carbazol‐9‐yl)hexyl)piperazin‐1‐yl)‐N,N,N‐trimethylethanammonium iodide) showed a good anti‐proliferative activity toward breast cancer cells, causing apoptosis by activation of the caspase pathway. Interestingly, the activity of these two compounds on triple‐negative MDA‐MB‐231 cells, which tend to be highly metastatic and aggressive, is strictly connected to the observed inhibition of hTopo II.

Use of graphene oxide functionalized with Grubbs and Hoveyda Grubbs catalyst to activate metathesis reaction in epoxy mixtures

In this paper we discuss the possibility to use graphite oxide functionalized with Grubbs and Hoveyda Grubbs catalysts to activate metathesis reactions in epoxy mixtures.