Paolo Sgarbossa

Supramolecular control on chemo- and regioselectivity via encapsulation of (NHC)-Au catalyst within a hexameric self-assembled host

The encapsulation of a Au(I) catalyst within a self-assembled, hydrogen bonded, hexameric capsule dramatically changes its catalytic activity, leading to unusual products due to the steric requirements of the hosts cavity.

Catalytic Asymmetric Baeyer–Villiger Oxidation in Water by Using PtII Catalysts and Hydrogen Peroxide: Supramolecular Control of Enantioselectivity

The enantioselective Baeyer-Villiger oxidation of cyclic ketones is a challenging reaction, especially when using environmentally friendly oxidants. The reaction was carried out in water by using soft Lewis acid Pt(II) complexes that have chiral diphosphines as well as monophosphines. Addition of a surfactant is crucial, which leads to the formation of micelles that act as nanoreactors in which the substrate and catalyst encounter each other in an ordered medium that in several cases positively influences both the conversion and the selectivity of the reactions. This is due to the combination of the hydrophobic effect (which confines the components of the reaction in the micelles), together with supramolecular interactions between the partners within the ordered palisade provided by the alkyl chains of the surfactant. For the oxidation of meso-cyclobutanones, addition of surfactant allowed the reaction to proceed in high yields and the enantiometic excess (ee; 56%) was higher than in organic solvents. Subsequent extension to meso-cyclohexanones resulted in a general decrease in yields but an enhancement of enantioselectivity (ee up to 92%) moving from organic to water-surfactant media, regardless of the substrate or the catalyst employed. Different behaviour was observed with chiral cyclobutanones 7 and 10: with 7 the best catalyst was 1 g, whereas with the larger substrate, 10, complexes 1 a-b performed better in terms of enantioselectivity. Each combination of substrate, catalyst and surfactant is a new system and supramolecular reciprocal interactions together with the hydrophobic character of the counterparts play crucial roles. The asymmetric Baeyer-Villiger oxidation in water catalyzed by 1 a-h in the presence of micelles is a viable reaction that often benefits from the hydrophobic effect, leading to substantial increases in enantioselectivity.

Chemistry and biological activity of platinum amidine complexes.

Platinum amidine complexes represent a new class of potential antitumor drugs that contain the imino moiety HNC(sp2) bonded to the platinum center. They can be related to the iminoether derivatives, which were recently shown to be the first PtII compounds with a trans configuration endowed with anticancer activity. The chemical and biological properties of platinum amidine complexes, and more generally of platinum imino derivatives, can be rationally modified through suitable synthetic procedures with the aim of improving their cytotoxicity and antitumor activity. The addition of protic nucleophiles to nitriles coordinated to platinum in various oxidation states can offer a wide variety of complexes with chemical, structural, and physical properties specifically tuned for a more efficacious biological response.

Transition metal coordination and reactivity of 2-(azidomethyl)-, 2-(chloromethyl)- and 2-(iodomethyl)phenyl isocyanides

Abstract 2-(Azidomethyl)phenyl isocyanide, 2-(CH 2 N 3 )C 6 H 4 NC (AziNC), coordinates to {M(CO) 5 } (M=W, Cr) fragments to afford the corresponding isocyanide complexes [M(CO) 5 (AziNC)] (M=W ( 1 ), Cr ( 2 )). AziNC coordinates also to some Au(I) species such as [AuCl(AziNC)] ( 3 ), derived from the reaction of [AuCl(Me 2 S)] with AziNC, and [Au(AziNC) 2 ][BF 4 ] ( 4 ), obtained from the reaction of 3 with AgBF 4 , followed by treatment with AziNC. Complexes 1 and 2 undergo the Staudinger reaction with PPh 3 affording the phosphinimine-isocyanide derivatives [M(CO) 5 {CNC 6 H 4 -2-(CH 2 NPPh 3 )}] (M=W ( 5 ), Cr ( 6 )). Complex 6 reacts with H 2 O affording a mixture of the amino–isocyanide [Cr(CO) 5 {CNC 6 H 4 -2-(CH 2 NH 2 )}] ( 7 ) and the carbene [Cr(CO) 5 { CN(H)C 6 H 4 -2-CH 2 N (H)}] ( 8 ) species. Complexes 3 and 4 react with 1 or 2 equiv. of PPh 3 displacing the isocyanide with the formation of the complexes [AuCl(PPh 3 )] ( 9 ) and [Au(PPh 3 ) 2 ][BF 4 ] ( 10 ), respectively. The halogeno–isocyanide complexes [W(CO) 5 (CNC 6 H 4 -2-CH 2 Cl)] ( 11 ) and [W(CO) 5 (CNC 6 H 4 -2-CH 2 I)] ( 12 ) show different reactivity towards amines so that only 12 reacts with MeNH 2 to afford in low yield the N -heterocyclic carbene species [W(CO) 5 { CN(H)C 6 H 4 -2-CH 2 N (Me)}] ( 13 ).

Optimal inductor design for nanofluid heating characterisation

Purpose – Magnetic fluid hyperthermia experiment requires a uniform magnetic field in order to control the heating rate of a magnetic nanoparticle fluid for laboratory tests. The automated optimal design of a real-life device able to generate a uniform magnetic field suitable to heat cells in a Petri dish is presented. The paper aims to discuss these issues. Design/methodology/approach – The inductor for tests has been designed using finite element analysis and evolutionary computing coupled to design of experiments technique in order to take into account sensitivity of solutions. Findings – The geometry of the inductor has been designed and a laboratory prototype has been built. Results of preliminary tests, using a previously synthesized and characterized magneto fluid, are presented. Originality/value – Design of experiment approach combined with evolutionary computing has been used to compute the solution sensitivity and approximate a 3D Pareto front. The designed inductor has been tested in an experi...

Low toxicity and unprecedented anti-osteoclast activity of a simple sulfur-containing gem-bisphosphonate: A comparative study

Bisphosphonates (BPs) are key drugs for the treatment of bone resorption diseases like osteoporosis, Pagets disease and some forms of tumors. Recent findings underlined the importance of lipophilic N-containing BPs to ensure high biological activity. Herein we present some unprecedented results concerning the low toxicity and good anti-osteoclast activity of low molecular weight hydrophilic S-containing BPs. A series of S and N-containing BPs bearing aromatic and aliphatic substitution were prepared through Michael addition reaction between vinylidenebisphosphonate tetraethyl ester and the proper nucleophile under basic catalysis. S-containing BPs showed a generally low toxicity, determined with the neutral-red assay using the L929 cell line, and, in particular for an aliphatic one, a good biological activity assessed on primary cultures of human osteoclasts.

Synthesis and transition metal coordination of 2-(azidomethyl) phenyl isocyanide

Abstract The reaction of 2-(chloromethyl)phenyl formamide, 2-(CH2Cl)C6H4NHCHO, with NaN3 in DMSO at room temperature affords 2-(azidomethyl)phenyl formamide, 2-(CH2N3)C6H4NHCHO (1), which is then dehydrated to 2-(azidomethyl)phenyl isocyanide, 2-(CH2N3)C6H4NC, (2) upon reaction with SOCl2 in DMF at low temperature. The coordination ability of the isocyanide 2 has been tested towards some Pt(II), Pd(II) and W(0) metal complexes to yield derivatives of the type [PtCl2(CNC6H4-2-CH2N3)2], [PdCl2(CNC6H4-2-CH2N3)(PPh3)] and [W(CO)5(CNC6H4-2-CH2N3)], respectively.

Metal complexes with di(N-heterocyclic carbene) ligands bearing a rigid ortho-, meta or para-phenylene bridge

Three novel dinuclear bis-dicarbene silver(i) complexes of general formula [Ag2(MeIm-phenylene-MeIm)2](PF6)2 (Im = imidazol-2-ylidene) were synthesized. The corresponding copper(i) and gold(i) complexes were obtained by transmetalation of the di(N-heterocyclic carbene) ligand from the silver(i) species, and both coordination geometry and stoichiometry are maintained for all three group 11 metals as expected. The photophysical properties of the Ag(i) and Au(i) complexes were also investigated and discussed; in particular the most strongly emitting complex was also studied via DFT calculations. In addition, the ruthenium(ii) and iridium(iii) complexes [RuCl(MeIm-(o-phenylene)-MeIm)(p-cym)](PF6) and [IrClCp*(MeIm-(o-phenylene)-MeIm)](PF6) were prepared and shown to present in these cases a chelating coordination of the di(N-heterocyclic carbene) ligand.

Green Catalytic Baeyer–Villiger Oxidation with Hydrogen Peroxide in Water Mediated by PtII Catalysts

Baeyer–Villiger oxidation of cyclic ketones with 35 % hydrogen peroxide as a green oxidant mediated by monomeric PtII complexes bearing alkyl diphosphines greatly benefits from the employment of water with anionic surfactants as reaction medium. Under such conditions, the reaction shows enhanced catalytic activity compared to that with organic solvents. For more acid sensitive substrates, hydrolysis of the lactone product to the corresponding hydroxy acid occurs. Mild experimental conditions, such as moderate temperature and low catalyst loading (≤2 % mol), enabled moderate to good yields.

Synthesis, crystal structure, DNA and protein binding studies of novel binuclear Pd(II) complex of 6-methoxy-2-oxo-1,2-dihydroquinoline-3-carbaldehyde-4(N,N)-dimethylthiosemicarbazone

A novel binuclear palladium(II) complex [(AsPh3)2ClPd(L)PdCl] (LPd2) has been synthesized by reacting 2-oxo-1,2-dihydroquinoline-3-carbaldehyde-4(N,N)-dimethylthiosemicarbazone (HL) with [PdCl2(AsPh3)2], and the molecular structure was confirmed by single crystal X-ray diffraction studies. The DNA interactions of the free ligand and of the complex have been evaluated by absorption and ethidium bromide (EB) competitive studies which revealed that the complex could interact with calf thymus DNA (CT-DNA) through intercalation. In addition, the interactions with bovine serum albumin (BSA) were also studied showing that the new binuclear palladium complex had a strong binding affinity with BSA.