Eudesmanolides from Dimerostemma vestitum

A leaf rinse extract with dichloromethane from Dimerostemma vestitum afforded five new eudesmanolides (1-5) along with the known flavone eupafolin. Compounds 1-5 were isolated by chromatographic methods, and their structures were elucidated by spectral analyses. Eudesmanolides 1-4 show a functional group substitution pattern so far unreported in the subtribe Verbesininae (tribe Heliantheae) of the family Asteraceae.66340140

Synthesis, properties and gas phase collision-induced dissociation of the heptanuclear doubly bridged complex [Ru(bpy)(2)(BPE)(2){Ru3O(CH3COO)(6)(py)(2)}(2)](PF6)(4)

The [Ru(bpy)(2)(BPE)(2){Ru3O(CH3COO)(6)(py)(2)}(2)](PF6)(4) complex, in which bpy = 2,2'-bipyridine, BPE = trans-1,2-bis(4-pyridyl)ethylene and py = pyridine, provides an interesting case of a heptanuclear mixed compound containing two triangular [Ru3O] clusters attached to a ruthenium polypyridine center. The composition and structural properties of this doubly bridged complex were investigated by means of electrospray mass (ESI-MS) and tandem mass (ESI-MS/MS) spectrometric experiments and NMR spectroscopy (H-1 and C-13). The characteristic multi-isotopic distribution, 1/4 m/z peak separation and dissociation chemistry of the isotopologue [Ru(bpy)(2)(BPE)(2){Ru3O(CH3COO)(6)(py)(2)}(2)](4+) cation provided detailed and unequivocal MS characterization of the complex. In the electronic spectra of the heptanuclear complex broad bands were observed at 427 and 696 nm, and ascribed, respectively, to [Ru(bpy)(2)(BPE)(2)] metal-to-ligand charge-transfer and to [Ru3O] internal cluster transitions. The characteristic waves associated with the [Ru3O](1-/0/1+/2+/3+) redox couples were found at -1.02, 0.16, 1.20, 2.11 V (versus SHE) in the cyclic voltammograms. Another broad wave was observed at -1.22 V, involving superimposed bpy(0/-) and BPE0/1- redox processes, and a peculiar wave at 1.48 V. exhibiting only a half of the relative intensity, was assigned to the central Ru3+/2+ redox pair. Despite the two conjugated BPE bridges, the electrochemical and spectroelectrochemical data indicated only a weak coupling through the TU-system in the heptanuclear complex. (c) 2005 Elsevier Ltd. All rights reserved.24673173

Keto-enolic equilibria of an isatin-Schiff base copper(II) complex and its reactivity toward carbohydrate oxidation

An interesting isatin-Schiff base copper(II) complex, [Cu(isapn)](ClO(4))(2) where isapn N,N'-[bis-(3,3'-indolin-2-one)]-1,3-diiminepropane, was prepared and characterized by different techniques, both in the solid state and in solution, and its reactivity toward carbohydrate oxidation was verified. The positive ion electrospray mass spectrum detects the complex as an isotopologue cluster of singly charged intact isatin-copper(I) ions of m/z 395 (for 65 Cu) with an isotopic pattern identical to that calculated for C(19)H(16)CuN(4)O(2)(+). Tandem mass spectrometry reveals an interesting and structurally diagnostic collision-induced dissociation behavior for this ionized complex, which is dominated by the cleavage of the N-(CH(2))(3)-AN propylene bridge. In aqueous solution, this complex undergoes a peculiar keto-enolic equilibrium, verified at different pH's by spectroscopic methods (u.v.-vis. and e.p.r.), with a corresponding pK(a) determined as 9.5. The e.p.r. parameter ratio g(parallel to)/A(parallel to) for this complex, in frozen MeOH/H(2)O (4: 1, v/v) solution at 77 K, changes from 188 cm in acidic medium (pH 2.5-3.0) to 118 cm in basic medium (pH 11), indicating a significant structural change from a distorted tetrahedral to a more tetragonal geometry around the copper ion. This compound was shown to catalyze the oxidation of hexoses ( glucose, fructose and galactose), in alkaline media, via reactive oxygen species, which were detected by using specific enzymes, and by e.p.r. spin trapping. The reaction was monitored at (25.0 +/- 0.1)degreesC by the consumption of oxygen, and showed first-order dependence on catalyst, followed by a saturation effect. First-order kinetics with respect to [OH(-)] concentration was also observed, indicating that enolization of the substrate as well as the metal-catalyzed enediol oxidation are the rate-determining steps.29549550

Cyclization reactions of acylium and thioacylium ions with isocyanates and isothiocyanates: Gas phase synthesis of 3,4-dihydro-2,4-dioxo-2H-1,3,5-oxadiazinium ions

Gas-phase reactions of several acylium and thioacylium ions, that is H2C=N-C+=O, H2C=N-C+=S, O=C=N-C+=O, S=C=N-C+=O, H3C-C+=O, and (CH3)(2)N-C+=O, with both a model isocyanate and isothiocyanate, that is, C2H5-N=C=O and C2H5-N=C=S, were investigated using tandem-in-space pentaquadrupole mass spectrometry. In these reactions, the formation of mono- and double-addition products is observed concurrently with proton transfer products. The double-addition products are far more favored in reactions with ethyl isocyanate, whereas the reactions with ethyl isothiocyanate form, preferentially, either the mono-addition product or proton transfer products, or both. Retro-addition dominates the low-energy collision-induced dissociation of the mono- and double-addition products with reformation of the corresponding reactant ions. Ab initio calculations at Becke3LYP//6-311 + G(d,p) level indicate that cyclization is favored for the double-addition products and that products equivalent to those synthesized in solution, that is, of 3,4-dihydro-2,4-dioxo-2H-1,3,5-oxadiazinium. ions and sulfur analogs, are formed.16101602160

New iridium(I) complexes with labile ligands: reactivity and structural characterization by atmospheric pressure mass and tandem mass spectrometry

Reaction of diphosphine complexes [IrCl{(C6F5)(2)P(CH2)(2)P(C6F5)(2) }](2) (I) and [IrCl(dppe)](2) (II) with coordinating solvents (acetonitrile, acetone, DMSO) leads to several square-planar complexes of the type [IrCl(diphosphine)(solvent)] which are stable only in solution ([IrCl{(C6F5)(2)P(CH2)(2)P(C6F5)(2)}(NCCH3)] (III) and [IrCl{(C6F5)(2)P(CH2)(2)P(C6F5)(2)} (acetone)], IV) and/or can be detected only under APCI-MS/MS conditions ([IrCl(dppe)(solvent)]). When III is allowed to react with CO for at least 30 min, the unusual five coordinated trans-dicarbonyl complex [IrCl{(C6F5)(2)P(CH2)(2)P(C6F5)(2)}(CO)(2)] (Vb) is formed, as characterized by H-1 and P-31 NMR, FT-IR, TGA and APCI-MS/MS. A new and stable square-planar complex [Ir(OCH3)(cod)(PClPh2)] (IX) was also synthesized. Its APCI-MS/MS spectrum is simple and unique as it shows exclusively the loss of a neutral C3H2 species. Along with the APCI-MS and APCI-MS/MS analyses, whenever it was possible all complexes were also characterized by H-1 and P-31 NMR spectroscopy. (C) 2003 Elsevier B.V. All rights reserved.35772100210

Mannich-type reactions in the gas-phase: The addition of enol silanes to cyclic N-acyliminium ions

The intrinsic gas-phase reactivity of cyclic N-acyliminium ions in Mannich-type reactions with the parent enol silane, vinyloxytrimethylsilane, has been investigated by double- and triple-stage pentaquadrupole mass spectrometric experiments. Remarkably distinct reactivities are observed for cyclic N-acyliminium ions bearing either endocyclic or exocyclic carbonyl groups. NH-Acyliminium ions with endocyclic carbonyl groups locked in s-trans forms participate in a novel tandem N-acyliminium ion reaction: the nascent adduct formed by simple addition is unstable and rearranges by intramolecular trimethylsilyl cation shift to the ring nitrogen, and an acetaldehyde enol molecule is eliminated. An NSi(CH3)(3)-acyliminium ion is formed, and this intermediate ion reacts with a second molecule of vinyloxytrimethylsilane by simple addition to form a stable acyclic adduct. N-Acyl and NN-diacyliminium ions with endocyclic carbonyl groups, for which the s-cis conformation is favored, react distinctively by mono polar [4(+) + 2] cycloaddition yielding stable, ressonance-stabilized cycloadducts. Product ions were isolated via mass-selection and structurally characterized by triple-stage mass spectrometric experiments. B3LYP/6-311G(d,p) calculations corroborate the proposed reaction mechanisms.67144652465

Synthesis, spectroscopy, tandem mass spectrometry, and electrochemistry of the linearly bridged mu-{trans-1,4-bis[2(4-pyridyl)ethenyl]-benzene}-{Ru3O(CH3COO)(6)(py)(2)}(2) cluster

The novel polynuclear [{Ru3O(CH3COO)(6)(py)(2)}(2)(BPEB)](PF6)(2) species containing the linear bridging trans-1,4-bis[2-(4-pyridyl)ethenyl]-benzene ligand (BPEB) was synthesized and its structural characterization carried out by means of positive ion electrospray (ESI-MS) and tandem mass (ESI-MS/MS) spectrometry, as well as by H-1 NMR spectroscopy. The doubly charged cation [{Ru3O(CH3COO)(6)(py)(2))(2)(BPEB)](2+) was detected in the ESI-MS mass spectrum as a multiple-component isotopomeric ionic cluster centered at m/z 974, which ion abundance and m/z distribution matched perfectly the isotopic pattern calculated for this multiple isotope Ru-3-containing ion. The tandem mass spectrum of [ Ru3O(CH3COO)(6)(py)(2)}(2)(BPEB)](2+) provided a structural diagnostic dissociation behavior, on the basis of the characteristic charge splitting and sequential ligand loss steps. The cyclic voltammograms of the complex exhibited a quasi-reversible multistep redox behavior, displaying three waves at 1.14, 0.08, and -1.21 V ascribed to the [Ru3O](2+/1+/0/1-) processes and two waves at -1.56 and -1.78 V ascribed to the BPEBO0/1-/2- redox processes which are also observed in the free ligand, at -1.48 and 1.61 V, respectively. In spite of the conducting nature of the bridging ligand, the electrochemical and spectroelectrochemical results indicated a weak electronic coupling between the triangular cluster centers. (C) 2004 Published by Elsevier B.V.35782253226

{trans,-1,4-bis[(4-pyridyl)ethenyl]benzene}(2,2 '-bipyridine)ruthenium(II) complexes and their supramolecular assemblies with beta-cyclodextrin

Two novel ruthenium polypyridine complexes, [Ru(bpy)(2)Cl(BPEB)](PF6) and {[Ru(bpy)(2)Cl](2)(BPEB)}(PF6)(2) (BPEB = trans- 1,4-bis[2-(4-pyridyl)ethenyl]benzene), were synthesized and their characterization carried out by means of elemental analysis, UV-visible spectroscopy, positive ion electrospray (ESI-MS), and tandem mass (ESI-MS/MS) spectrometry, as well as by NMR spectroscopy and cyclic voltammetry. Cyclic and differential pulse voltammetry for the mononuclear complex showed three set of waves around 1.2 V (Ru2+/3+), -1.0 V (BPEB0/-), and -1.15 (BPEB-/2-). This complex exhibited aggregation phenomena in aqueous solution, involving pi-pi stacking of the planar, hydrophobic BPEB ligands. According to NMR measurements and variable-temperature experiments, the addition of beta-cyclodextrin (betaCD) to [Ru(bpy)(2)Cl(BPEB)](+) leads to an inclusion complex, breaking down the aggregated array.43113521352

On the identification of ionic species of neutral halogen dimers, monomers and pincer type palladacycles in solution by electrospray mass and tandem mass spectrometry

Electrospray (ESI) mass spectra analysis of acetonitrile solutions of a series of neutral chloro dimers, pincer type, and monomeric palladacycles has enabled the detection of several of their derived ionic species. The monometallic cationic complexes Pd[kappa(1) -C,kappa(1)-N, kappa(1)-S-C=(CH(3)S-2-C(6)H(4))C(Cl)CH(2)N(CH(3))(2)](+) (1a) and [Pd[kappa(1)-C,kappa(1)-N,kappa(1)-S-C=(CH(3)S-2-C(6)H(4))C(Cl)CH(2)N(CH(3))(2)](CH(3)CN)](+) (1b) and the bimetallic cationic complex [kappa(1)-C,kappa(1)-N,kappa(1)-S-C=(CH(3)S-2-C(6)H(4))C(Cl)CH(2)N(CH(3))(2)]Pd-Cl-Pd[kappa(1)-C,kappa(1)-N,kappa(1)-S-C=(CH(3)S2-C(6)H(4))C(Cl)CH(2)N(CH(3))(2)](+) (1c) were detected from an acetonitrile solution of the pincer palladacycles Pd[kappa(1)-C,kappa(1)-N,kappa(1)-S-C=(CH(3)S-2-C(6)H(4))C(Cl)CH(2)N(CH(3))(2)](Cl) 1. For the dimeric compounds {Pd[kappa(1)-C,kappa(1)-N-C=(Y-2-C(6)H(4))C(Cl)CH(2)N(CH(3))(2)](mu-Cl)}(2) (2, Y = H and 3, CF(3)), highly electronically unsaturated palladacycles [Pd[kappa(1)-C,kappa(1)-N-C=(Y-2-C(6)H(4))C(Cl)CH(2)N(CH(3))(2)](+) (2d, 3d) and their mono and di-acetonitrile adducts, namely, [Pd[kappa(1)-C,kappa(1)-N-C=(Y-2-C(6)H(4))C(Cl)CH(2)N(CH(3))(2)](CH(3)CN)](+) (2e, 3e) and [Pd[kappa(1)-C,kappa(1)-N-C=(Y-2-C(6)H(4))C(Cl)CH(2)N(CH(3))(2)](CH(3)CN)(2)](+) (2f and 3f) were detected together with the bimetallic complex [Pd[kappa(1)-C,kappa(1)-N-C=(Y-2-C(6)H(4))C(Cl)CH(2)N(CH(3))(2)]-Cl-Pd[kappa(1)-C,kappa(1)-N-C=(Y-2-C(6)H(4))C(Cl)CH(2)N](CH(3))(2)](+) (2a, 3a) and its acetonitrile adducts [kappa(1)-C,kappa(1)-N-C=(Y-2-C(6)H(4))C(Cl)CH(2)N(CH(3))(2)](CH(3)CN)Pd-Cl-Pd[kappa(1)-C,kappa(1)-N-C=(Y-2-C(6)H(4))C(Cl)CH(2)N(CH(3))(2)](+) (2b, 3b) and [kappa(1)-C,kappa(1)-N-C=(Y-2-C(6)H(4))C(Cl)CH(2)N(CH(3))(2)](CH(3)CN)Pd-Cl-Pd[kappa(1)-C,kappa(1)-N-C=(Y-2-C(6)H(4))C(Cl)CH(2)N(CH(3))(2)(CH(3)CN)](+) (2c, 3c). The dimeric palladacycle {Pd[kappa(1)-C,kappa(1)-N-C=(CH(3)O-2-C(6)H(4))C(Cl)CH(2)N(CH(3))(2)](mu-Cl)}(2) (4) is unique as it behaves as a pincer type compound with the OCH(3) substituent acting as an intramolecular coordinating group which prevents acetonitrile full coordination, thus forming the cationic complexes [(C(6)H(4)(o-CH(3))C=C(Cl)CH(2)N(CH(3))(2)-kappaO,kappaC,kappaN)Pd](+) (4b), [(C(6)H(4)(o-CH(3)O)C=C(Cl)CH(2)N(CH(3))(2)-kappaO,kappaC,kappaN)Pd(CH(3)CN)](+) (4c) and [(C(6)H(4) (o-MeO)C=C(Cl)CH(2)N(CH(3))(2)-kappaO,kappaC,kappaN)Pd-Cl-Pd(C(6)H(4)(o-CH(3)O)C=C(Cl)CH(2)N(CH(3))(2)-kappaO,kappaC,kappaN)](+) (4a). ESI-MS spectra analysis of acetonitrile solutions of the monomeric palladacycles Pd[kappa(1)-C,kappa(1)-N-C=(Y-2-C(6)H(4))C(Cl)CH(2)N(CH(3))(2)](Cl)(PY) (5, Y = H and 6, Y = CF(3)) allows the detection of some of the same species observed in the spectra of the dimeric palladacycles, i.e., monometallic cationic 2d-3d, 2e-3e and {Pd[kappa(1)-C,kappa(1)-N-C=(Y-2-C(6)H(4))C(Cl)CH(3)N(CH(3))(2)](PY)}(+) (5a, 6a) and {Pd[kappa(1)-C,kappa(1)-N-C=(Y-2-C(6)H(4))C(Cl)CH(2)N(CH(3))(2)](CH(3)CN)(PY)}(+) (5b, 6b) and the bimetallic 2a, 3a, 2b, 3b, 2c and 3c. In all cationic complexes detected by ESI-MS, the cyclometallated moiety was intact indicating the high stability of the four or six electron anionic chelate ligands. The anionic (chloride) or neutral (pyridine) ligands are, however, easily replaced by the acetonitrile solvent. (C) 2004 Elsevier B.V. All rights reserved.35782349235

Fiber introduction mass spectrometry: Fully direct coupling of solid-phase microextraction with mass spectrometry

This work describes the first fully direct coupling of solid-phase microextraction (SPME) with mass spectrometry. An inlet system using a septum as the only interface between the ambient and the high-vacuum mass spectrometer was constructed to allow the introduction of the SPME needle directly into the ionization region of a mass spectrometer. The PDMS-coated fiber was then placed and exposed exactly between the two ionization filaments. Uniform heating of the fiber, efficient thermal desorption, and electron ionization of the analytes were achieved. Using this new analytical technique, here termed fiber introduction mass spectrometry (FIMS), we have been able to detect and quantitate several volatile (VOC) and semivolatile (SVOC) organic chemicals (carbon tetrachloride, benzene, toluene, xylenes, gamma-terpinene, diisoamyl ether, chlorobenzene, and many PAHs) and two herbicides (Sylvex and its methyl ether) from aqueous solutions at low-ppb to ppt levels using either SPME headspace or solution extraction. FIMS shows high sensitivity (ng/L), good reproducibility, and accuracy, providing therefore a simple and effective approach to rapid analysis of VOC and SVOC in various matrixes.74215688569