Alkynyldiphenylphosphine d8 (Pt, Rh, Ir) complexes: contrasting behavior toward cis-[Pt(C6F5)2(THF)2

The synthesis and characterization of a series of mononuclear d(8) complexes with at least two P-coordinated alkynylphosphine ligands and their reactivity toward cis-[Pt(C(6)F(5))(2)(THF)(2)] are reported. The cationic [Pt(C(6)F(5))(PPh(2)C triple-bond CPh)(3)](CF(3)SO(3)), 1, [M(COD)(PPh(2)C triple-bond CPh)(2)](ClO(4)) (M = Rh, 2, and Ir, 3), and neutral [Pt(o-C(6)H(4)E(2))(PPh(2)C triple-bond CPh)(2)] (E = O, 6, and S, 7) complexes have been prepared, and the crystal structures of 1, 2, and 7.CH(3)COCH(3) have been determined by X-ray crystallography. The course of the reactions of the mononuclear complexes 1-3, 6, and 7 with cis-[Pt(C(6)F(5))(2)(THF)(2)] is strongly influenced by the metal and the ligands. Thus, treatment of 1 with 1 equiv of cis-[Pt(C(6)F(5))(2)(THF)(2)] gives the double inserted cationic product [Pt(C(6)F(5))(S)mu-(C(Ph)=C(PPh(2))C(PPh(2))=C(Ph)(C(6)F(5)))Pt(C(6)F(5))(PPh(2)C triple-bond CPh)](CF(3)SO(3)) (S = THF, H(2)O), 8 (S = H(2)O, X-ray), which evolves in solution to the mononuclear complex [(C(6)F(5))(PPh(2)C triple-bond CPh)Pt(C(10)H(4)-1-C(6)F(5)-4-Ph-2,3-kappaPP'(PPh(2))(2))](CF(3) SO(3)), 9 (X-ray), containing a 1-pentafluorophenyl-2,3-bis(diphenylphosphine)-4-phenylnaphthalene ligand, formed by annulation of a phenyl group and loss of the Pt(C(6)F(5)) unit. However, analogous reactions using 2 or 3 as precursors afford mixtures of complexes, from which we have characterized by X-ray crystallography the alkynylphosphine oxide compound [(C(6)F(5))(2)Pt(mu-kappaO:eta(2)-PPh(2)(O)C triple-bond CPh)](2), 10, in the reaction with the iridium complex (3). Complexes 6 and 7, which contain additional potential bridging donor atoms (O, S), react with cis-[Pt(C(6)F(5))(2)(THF)(2)] in the appropriate molar ratio (1:1 or 1:2) to give homo- bi- or trinuclear [Pt(PPh(2)C triple-bond CPh)(mu-kappaE-o-C(6)H(4)E(2))(mu-kappaP:eta(2)-PPh(2)C triple-bond CPh)Pt(C(6)F(5))(2)] (E = O, 11, and S, 12) and [(Pt(mu(3)-kappa(2)EE'-o-C(6)H(4)E(2))(mu-kappaP:eta(2)-PPh(2)C triple-bond CPh)(2))(Pt(C(6)F(5))(2))(2)] (E = O, 13, and S, 14) complexes. The molecular structure of 14 has been confirmed by X-ray diffraction, and the cyclic voltammetric behavior of precursor complexes 6 and 7 and polymetallic derivatives 11-14 has been examined.     

HERPES VIRUS PRODUCTION IN MONKEY KIDNEY AND HUMAN SKIN CELLS TREATED WITH ANGELICIN OR 8-METHOXYPSORALEN PLUS 365 nm LIGHT

Abstract—At an cquimolar concentration of 50 μM the bifunctional furocoumarin, 8-methoxypsoralen (8-MOP), is about 36 times more efficient in inhibiting the colony forming ability of CV-I monkey kidney cells than the monofunctional furocoumarin angelicin. In contrast 8-MOP is only 7.5 times more efficient than angelicin for the inhibition of herpes simplex virus (HSV) production in CV-1 cells. This latter factor seems to reflect differences in photoreactivity of the two compounds with host cell DNA.
A substantial recovery of HSV production was seen when cells were infected at different time intervals after treatment with angelicin-plus-light, whereas recovery was very limited after 8-MOP plus light treatment. The recovery process was slow as compared to that observed after UV (254 nm)-irradiation.
The repair capacities of treated normal and xeroderma pigmentosum (group A) skin fibroblasts were estimated by measuring HSV production and unscheduled DNA synthesis. XP-A cells repaired angelicin induced damage less efficiently than did normal cells. Neither cell type showed any repair activity after 8-MOP plus light treatment.     

Organo-Polyoxometalate-Based Hydrogen-Bond Catalysis

Several urea-inserted organo-polyoxometalates (POMs) derived from polyoxotungstovanadate [P₂V₃W₁₅O₆₁]⁹⁻ were prepared. The insertion of the carbonyl into the polyoxometallic framework activates the urea toward Hydrogen-bond catalysis. This was shown on the Friedel-Crafts arylation of trans-β-nitrostyrene. Modelling shows that the most stable form of the organo-POMs features a cis-trans arrangement of the two N−H bonds, but that the likely catalytically active trans-trans form is accessible at room temperature. Finally, it is possible that the oxo substituents next to the vanadium atoms may help the approach of the nucleophile via H-bonding.     

Synthesis and characterization of TiO2/Rh3+ nanoparticulate sols, xerogels and cryogels for photocatalytic applications

Nanoparticulate TiO₂/Rh³⁺ sols have been synthesized by the colloidal sol?Cgel route. The combination of the data measured with optical techniques such as laser diffraction, dynamic light scattering and multiple light scattering with a near-infrared light allows us to follow up the evolution of the peptization process and to establish the effect of the presence of Rh³⁺ on it. It is observed that the presence of rhodium ions retards the peptization step (t₂) and decreases both the average particle size of the nanoparticles and the viscosity of the nanoparticulate sols. In addition, when Rh³⁺ is present the isoelectric point shifts up to higher pH, which suggests that chemical adsorption of the rhodium (III) cations onto the surface of the TiO₂ nanoparticles is produced. The xerogels and cryogels obtained from the sols are constituted by anatase as major phase and traces of brookite. The phase transition is observed at lower temperatures for the xerogels containing rhodium (III) and at higher temperatures in the case of the cryogels. Finally, photocatalytic activity is higher in the case of the TiO₂/Rh³⁺ sols due to the rhodium (III) effect on the electronic transitions from the valence band to the conduction band.     

Thermal study of l-alanine, l-threonine, and taurine crystals related to hydrogen bonding

In this study l-alanine, l-threonine, and taurine crystals were characterized through dilatometric technique and thermogravimetric and differential thermal analysis. The dilatometric analysis shows that the thermal expansion of the crystals is correlated with the strengths of local hydrogen bonding in the amino acid structures at room temperature. Thermogravimetric analysis and differential thermal analysis of the l-alanine, taurine, and l-threonine crystals have been performed at high temperatures. No clear correlation between the hydrogen bonding strengths and endothermic peak positions was observed.     

Preparation and evaluation of carbon-supported catalysts for ethanol oxidation

Supported PtSnIr/C, PtSn/C, and IrSn/C catalysts with potential application in a direct alcohol fuel cell were prepared by chemical reduction employing Pechini methodology. The catalyst particles were characterized by high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy (XPS). Linear sweep voltammetry (LV), chronoamperometry, and electrochemical impedance spectroscopy (EIS) measurements were performed by using a glassy carbon working electrode covered with the catalyst in a 1 M ethanol?+?0.5 M H₂SO₄ solution at 60 °C. It was demonstrated through XPS that PtSnIr/C and IrSn/C contain both IrO₂ and SnO₂. LV and chronoamperometry show a better catalytic behavior for ethanol oxidation on PtSnIr/C in the low-potential region and the improvement is attributed to the presence of both Sn and Ir oxides. The EIS accurately established that PtSnIr/C improved ethanol oxidation at lower potentials than PtSn/C.