Massimiliano Arca

[Au2(phen2Me)2(μ-O)2](PF6)2, a Novel Dinuclear Gold(III) Complex Showing Excellent Antiproliferative Properties

A novel dioxo-bridged dinuclear gold(III) complex with two 2,9-dimethylphenanthroline ligands was synthesized and thoroughly characterized. Its crystal structure was solved, and its solution behavior assessed. Remarkably, this compound revealed excellent antiproliferative properties in vitro against a wide panel of 36 cancer cell lines, combining a high cytotoxic potency to pronounced tumor selectivity. Very likely, these properties arise from an innovative mode of action (possibly involving histone deacetylase inhibition), as suggested by COMPARE analysis. In turn, electrospray ionization-mass spectrometry studies provided valuable insight into its molecular mechanisms of activation and of interaction with protein targets. Gold(III) reduction, dioxo bridge disruption, coordinative gold(I) binding to the protein, and concomitant release of the phenanthroline ligand were proposed to occur upon interaction with superoxide dismutase, used here as a model protein. Because of the reported results, this new gold(III) compound qualifies itself as an optimal candidate for further pharmacological testing.

CHARGE-TRANSFER ADDUCTS BETWEEN DONORS CONTAINING CHALCOGENS (S AND SE) AND DI-IODINE : SOLUTION STUDIES

Abstract The solution equilibria related to the 1:1 charge-transfer adduct formation between molecular iodine and several substrates containing sulfur and selenium donor atoms have been reviewed and the corresponding thermodynamic parameters ( K and Δ H °) reported for a series of thiones, selones, sulfides and selenides. A survey of the several calculation methods, based on UV–vis and in some cases 13 C-NMR spectroscopies, is also reported. Although the methods and techniques employed are very different, some correlations between the thermodynamic parameters and other experimental data, such as ν (II) Raman frequencies or UPS-binding energies, are reviewed and general conclusions drawn.

Photoinduced conductivity and nonlinear optical properties of [M(R,R′timdt)2] dithiolenes (M=Ni, Pd, Pt; R,R′timdt=monoreduced imidazolidine-2,4,5-trithione) as materials for optically driven switches and photodetectors

Abstract The unusual NIR-photoconducting properties of [M(Et,Pent-timdt)2] neutral dithiolenes (M=Ni, Pd, Pt; Et,Pent-timdt=monoreduced N-ethyl,N′-pentylimidazolidine-2,4,5-trithione) have been investigated with the aim of developing wavelength-selective air-stable photodetectors. In addition, the ps time-resolved dynamics of the absorption saturation has been studied on the Pd-complex by means of pump–probe experiments.

New perspectives in phosphonodithioate coordination chemistry. Synthesis and X-ray crystal structure of trans-bis-[O-ethyl-(4-methoxyphenyl)phosphonodithioato] nickel(II)

Abstract Attempts to optimise the synthesis of a new class of nickel(II) dithiolene complexes starting from 1,3-dialkylimidazolidine-2-thione-4,5-dione (1) and Lawessons reagent (2) have afforded a new and easy one-step synthesis of phosphonodithioate nickel(II) complexes. This consists of the direct reaction between NiCl2 and Lawessons reagent in the appropriate alcohol R′OH (R=Me, Et, i-Pr, Bu, Bz) as solvent, to give the bis-[O-alkyl/aryl-(4-methoxyphenyl)phosphonodithioato] nickel(II) complexes (5a–e) with high yields (64–91%). Among them, trans-bis-[O-ethyl-(4-methoxyphenyl)phosphonodithioato] nickel(II) (5b) was characterised by means of X-ray diffraction measurements on a single crystal. The compound crystallises in the triclinic, P 1 space group with a=6.4840(7), b=7.6032(9), c=13.055(2) A, α=99.481(9), β=99.43(1), γ=104.487(9)° and Z=1. The compound is centrosymmetric and exhibits discrete monomeric units with the ligand acting as S,S-bidentate. To explain the reactivity of Lawessons reagent, the formation of 4-methoxyphenyldithiophosphorane (6) as intermediate has been suggested. The reaction was also tested for Pd(II) and Pt(II), but in these cases the yields were not as satisfactory as for Ni(II).

Marked Increase in PROP Taste Responsiveness Following Oral Supplementation with Selected Salivary Proteins or Their Related Free Amino Acids

The genetic predisposition to taste 6-n-propylthiouracil (PROP) varies among individuals and is associated with salivary levels of Ps-1 and II-2 peptides, belonging to the basic proline-rich protein family (bPRP). We evaluated the role of these proteins and free amino acids that selectively interact with the PROP molecule, in modulating bitter taste responsiveness. Subjects were classified by their PROP taster status based on ratings of perceived taste intensity for PROP and NaCl solutions. Quantitative and qualitative determinations of Ps-1 and II-2 proteins in unstimulated saliva were performed by HPLC-ESI-MS analysis. Subjects rated PROP bitterness after supplementation with Ps-1 and II-2, and two amino acids (L-Arg and L-Lys) whose interaction with PROP was demonstrated by 1H-NMR spectroscopy. ANOVA showed that salivary levels of II-2 and Ps-1 proteins were higher in unstimulated saliva of PROP super-tasters and medium tasters than in non-tasters. Supplementation of Ps-1 protein in individuals lacking it in saliva enhanced their PROP bitter taste responsiveness, and this effect was specific to the non-taster group.1H-NMR results showed that the interaction between PROP and L-Arg is stronger than that involving L-Lys, and taste experiments confirmed that oral supplementation with these two amino acids increased PROP bitterness intensity, more for L-Arg than for L-Lys. These data suggest that Ps-1 protein facilitates PROP bitter taste perception and identifies a role for free L-Arg and L-Lys in PROP tasting.

Simultaneous decomposition of several spectra into the constituent Gaussian peaks

A computer program is proposed for the decomposition of spectra into their constituent Gaussian peaks. A new feature of this program is the possibility of operating on different spectra from two or more components of variable concentration at the same time, by optimising the wavelengths of the maxima and the halfbandwidths of all the spectra while the height of each peak is optimized in each single spectrum. This distinct treatment is possible due to the fact that the Gaussian functions are linear with respect to the heights and non-linear with respect to the remaining parameters. A linear and non-linear least-squares analysis, respectively, is therefore possible. Besides its intrinsic utility in handling spectral data of different origin this procedure proves more useful than the single spectrum decomposition both in increasing the reliability of the parameters and in improving the convergence properties of the procedure.

Colorimetric response to anions by a "robust" copper(II) complex of a [9]aneN3 pendant arm derivative: CN- and I- selective sensing.

The 1 : 1 complex [Cu(L)](BF(4))(2)·MeCN (1) of the tetradentate ligand 1-(2-quinolinylmethyl)-1,4,7-triazacyclononane (L) selectively changes its colour in the presence of CN(-) in H(2)O and MeCN (without undergoing decomplexation from the macrocyclic ligand). The same complex in MeCN assumes different colours in the presence of CN(-) or I(-).

From mono- to poly-substituted frameworks: a way of tuning the acidic character of C(c)-H in o-carborane derivatives.

The incorporation of iodine atoms onto the boron vertices of the o-carborane framework causes, according to spectroscopic data, a uniform increase in the acidic character of the C(c)-H (C(c)= cluster carbon) vertices, whereas the incorporation of methyl groups onto the boron vertices of the o-carborane framework reduces their acidity. Methyl groups when attached to boron are electron-withdrawing in boron clusters, whereas iodine atoms bonded to boron act as electron donors. This has been proven on B-methyl and B-iodinated o-carboranes with NMR spectroscopy measurements and DFT calculations of natural bond orbital (NBO) charges, which show a cumulative buildup of positive cluster-only total charge (CTC) on B-methyl o-carboranes and a cumulative buildup of negative cluster-only total charge for B-iodinated o-carboranes.

Ring-Opening of Lawesson’s Reagent: New Syntheses of Phosphono- and Amidophosphono-Dithioato Complexes − Structural and CP-MAS31P-NMR Characterization of [p-CH3OPh(X)PS2]2M (X = MeO,iPrNH; M = NiII, PdII, and PtII)

The opening of the P2S2 tetraatomic ring of Lawesson’s reagent (4) has proved versatile in synthesizing phosphono- and amidophosphono-dithioato mononuclear complexes [p-CH3OPh(X)PS2]2M [X = CH3O, iPrNH; M = NiII, PdII, PtII]. A one-step reaction of 4 with the appropriate metal salt in CH3OH, or in the presence of a stoichiometric amount of iPrNH2 in CHCl3, is used in the direct synthesis of the NiII and PdII complexes, but does not work in the PtII complexes. Alternatively, these syntheses can be carried out: i) by preparation and isolation of O-methyl(4-methoxyphenyl)phosphonodithioate (6) salts or isopropylamido(4-methoxyphenyl)- phosphonodithioate (7) salts by treating 4 with CH3O− in CH3OH or with iPrNH2, respectively; ii) by reaction of 6 or 7 with MCl2 or K2MCl4 [M = NiII, PdII, PtII] to give trans-bis[O-methyl(4-methoxyphenyl)phosphonodithioato]M and trans-bis[isopropylamido(4-methoxyphenyl)phosphonodithioato]M complexes. Following these routes, trans-bis[O-methyl(4-methoxyphenyl)phosphonodithioato]M [M = Ni (8a), Pd (8b), and Pt (8c)] and trans-bis[isopropylamido(4-methoxyphenyl)phosphonodithioato]M [M = Ni (9a), Pd (9b), and Pt (9c)] complexes have been synthesized and fully characterized by FAB mass, FT-IR, FT-Raman, UV/Vis, and CP-MAS 31P-NMR spectroscopy; the crystal structures of 7, 8b, 8c, and 9a are also reported.

Interaction of Methimazole with I2: X-ray Crystal Structure of the Charge Transfer Complex Methimazole−I2. Implications for the Mechanism of Action of Methimazole-Based Antithyroid Drugs

The antithyroid drug methimazole (MMI) reacts with molecular iodine to form, in a multistep process, 1-methylimidazole as final product. In this process, the charge transfer complex MMI-I 2 and the ionic disulfide [(C 4H 6N 2S-) 2] (2+) ( 1, dication MMI disulfide) have been isolated and their X-ray crystal structures solved. Dication MMI disulfide perchlorate acts effectively both in reducing I 2 to I (-) ions and in showing antioxidant properties in inactivating the enzyme lactoperoxidase compound I.