Raphael G. Raptis

A FeIII/Oxo Cubane Contained in an Octanuclear Complex of T Symmetry That Is Stable Over Five Oxidation States

Encapsulated in a protective [{Fe(pz)3 }4 ] outer layer, which provides the complex with structural stability, the octanuclear complex [Fe8 (μ4 -O)4 (μ-pz)12 Cl4 ] contains a Fe4 O4 core (see drawing) that withstands four consecutive reversible one-electron reductions. Iron-oxygen clusters are shown to possess redox properties which rival those of their better studied iron-sulfur analogues. pz=pyrazolate anion.

Bipinnatins K–Q, Minor Cembrane-Type Diterpenes from the West Indian Gorgonian Pseudopterogorgia kallos: Isolation, Structure Assignment, and Evaluation of Biological Activities⊥

An extensive chemical study of the secondary metabolites found in the crude organic extract of the gorgonian octocoral Pseudopterogorgia kallos has led to the isolation of seven new cembranolides, bipinnatins K-Q ( 2- 8), and one known compound, bipinnatin E ( 9). The molecular structures of compounds 2- 8, many of which contain unusual structural features, were assigned mainly by 2D NMR spectroscopic methods and X-ray crystallographic analysis. The discovery of compounds 2- 8 may lend support to previously proposed mechanisms for the biosynthesis of recently isolated bioactive natural products from the same gorgonian specimen. The in vitro cytotoxicity of bipinnatins 4, 6, and 7 against the NCI tumor cells MCF breast cancer, NCI-H460 non-small cell lung cancer, and SF-268 CNS cancer was evaluated. However, only bipinnatin Q ( 6) displayed significant cytotoxic activity. Some of the compounds isolated proved to be inhibitors of acetylcholine receptors.

Solution identification and solid state characterisation of a heterometallic polyoxometalate {Mo11V7}: (Mo11V5V)-V-VI (V2O52)-O-IV(mu(9)-SO3) (7-)

A polyoxomolybdenum/vanadium-sulfite {M(18)} cluster-based compound, [Mo(VI)(11)V(V)(5)V(IV)(2)O(52)(mu(9)-SO(3))](7-), is reported that exhibits a unique structural motif, arising from the incorporation of five V(V) and two V(IV) ions into a {M(18)} cluster framework templated by SO(3)(2-); this cluster compostion was first identified using cryospray mass spectrometry.

Tuning of the [Cu3(μ-O)]4+/5+ Redox Couple: Spectroscopic Evidence of Charge Delocalization in the Mixed-Valent [Cu3(μ-O)]5+ Species

Trinuclear Cu (II)-complexes of formula [Cu (II) 3(mu 3-E)(mu-4-R-pz) 3X 3] (+/- n ), E = O and OH; R = H, Cl, Br, CH(O) and NO 2; X = Cl, NCS, CH 3COO, and py, have been synthesized and characterized and the effect of substitution of terminal ligands, as well as 4-R-groups, in the one-electron oxidation process has been investigated by cyclic voltammetry. In situ UV-vis-NIR spectroelectrochemical characterization of the mixed valence Cu 3 (7+)-complex [Cu 3(mu 3-O)(mu-pz) 3Cl 3] (-) revealed an intervalence charge transfer band at 9550 cm (-1) (epsilon = 2600 cm (-1) M (-1)), whose analysis identifies this species as a delocalized, Robin-Day class-III system, with an electronic coupling factor, H ab, of 4775 cm (-1).

Metal tetraphosphonate "wires" and their corrosion inhibiting passive films.

Herein, we describe the preparation and characterization of five new divalent metal tetraphosphonates, M-HDTMP [M = Mg(2+), Ca(2+), Sr(2+), Ba(2+), and Cu(2+); HDTMP = hexamethylenediaminetetrakis(methylenephosphonate) dianion]. Materials {Sr[(HDTMP)(H(2)O)(6)] x 2 H(2)O}(n) (1), {Ba[(HDTMP)(H(2)O)(6)] x 2 H(2)O}(n) (2), and {Cu[(HDTMP)(H(2)O)(4)] x 6 H(2)O}(n) (3), as well as (en)(HDTMP) x 2 H(2)O (en = ethylenediammonium cation) have been structurally characterized. Structures depend on the coordination requirements of the M(2+) center and waters of crystallization content. The formation and characterization of effective anticorrosion passive films of M-HDTMP (M = Sr(2+) and Ba(2+)) are also reported.

Dolabellane-Type Diterpenoids with Antiprotozoan Activity from a Southwestern Caribbean Gorgonian Octocoral of the Genus Eunicea

Ten new diterpenes, 1-10, having a dolabellane skeleton were isolated from a Colombian gorgonian coral of the genus Eunicea. Their structures, as well as those of known compounds 11-18, were determined on the basis of spectroscopic analysis and, in some instances, by chemical conversion and X-ray crystallographic analysis. The absolute structure of 7 was established by chemical conversion from 11, a co-occurring dolabellane congener of known absolute structure. Most of these diterpenoids showed antimalarial activity against the protozoan parasite Plasmodium falciparum.

Synthesis and Characterization of Palladium and Palladium–Cobalt Nanoparticles on Vulcan XC-72R for the Oxygen Reduction Reaction

A single-source approach was used to synthesize bimetallic nanoparticles on a high-surface-area carbon-support surface. The synthesis of palladium and palladium-cobalt nanoparticles on carbon black (Vulcan XC-72R) by chemical and thermal reduction using organometallic complexes as precursors is described. The electrocatalysts studied were Pd/C, Pd2Co/C, and PdCo2/C. The nanoparticles composition and morphology were characterized using inductively coupled plasma mass spectrophotometer (ICP-MS), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray fluorescence spectroscopy (EDS), X-ray diffraction (XRD), and transmission electron microscopy (TEM) techniques. Electrocatalytic activity towards the oxygen reduction reaction (ORR) and methanol tolerance in oxygen-saturated acid solution were determined. The bimetallic catalyst on carbon support synthetized by thermal reduction of the Pd2Co precursor has ORR electrocatalytic activity and a higher methanol tolerance than a Pt/C catalyst.

A Mixed-Valence Octanuclear Iron-Oxo Pyrazolate : Assessment of Electronic Delocalization by Structural and Spectroscopic Analysis

A formally Fe(III)(7)Fe(II) complex, containing an inner Fe(4)O(4)-cubane and four peripheral Fe centers, is derived from the one-electron reduction of its Fe(III)(8) precursor. Spectroscopic analysis of the former reveals that the redox activity of this Fe(8) system is confined within its cubane core. The resulting (Fe(4)O(4))(3+)-cubane, which is valence-delocalized in the NMR, Mössbauer, and IR spectroscopy time scales but valence-trapped in the X-ray photoelectron spectroscopy (XPS) time scale, is better described as a Robin-Day class-II system by the analysis of its near-infrared (NIR) intervalence charge transfer (IVCT) band profile.

A novel polyoxo(thio)molybdenum(V) sulfite compound: Synthesis and crystal structure of {[Mo2V(μ-S)2O2]6(μ3-SO3)4(μ-SO3)12}20− anion

The non-cyclic polyoxo(thio)molybdate(V)-sulfite K6(NH4)14{[Mo2V(μ-S)2O2]6(μ3-SO3)4(μ-SO3)12}·7H2O 1 was prepared by self-condensation of [Mo2V(μ-S)2O2]2+ building block in the presence of (NH4)2SO3. Compound 1 was characterized by X-ray structure analysis as well as IR, UV-vis spectroscopies and thermogravimetric analysis.

Structure of [3,5-(C6H5)2C3H2N2]4. A 3,5-diphenylpyrazole tetramer linked by hydrogen bonds

3,5-Diphenylpyrazole, C 15 H 12 N 2 , M r =220.1, monoclinic, C2/c (No. 15), a=16.948 (4) A, b=17.163 (4) A, c=17.677 (6) A, β=109.59 (2) o . V=4844 (2) A 3 , Z=32, D x =1.21 Mg m -3 . λ(Mo Kα)=0.71069 A, μ=0.07 mm -1 , F(000)=1861.6, T=298 K, final R=0.056 and wR=0.058 for 259 variable parameters and 2073 reflections with F 0 2 >3σ(F 0 2 ). The asymmetric unit consists of a hydrogen-bonded dimer of 3,5-diphenylpyrazole which is further hydrogen bonded to form four discrete tetrameric aggregates per unit cell