Localization of cyclopropyl groups and alkenes within glycerophospholipids using gas-phase ion/ion chemistry

Shotgun lipid analysis using electrospray ionization tandem mass spectrometry (ESI-MS/MS) is a common approach for the identification and characterization of glycerophohspholipids GPs. ESI-MS/MS, with the aid of collision-induced dissociation (CID), enables the characterization of GP species at the headgroup and fatty acyl sum compositional levels. However, important structural features that are often present, such as carbon–carbon double bond(s) and cyclopropane ring(s), can be difficult to determine. Here, we report the use of gas-phase charge inversion reactions that, in combination with CID, allow for more detailed structural elucidation of GPs. CID of a singly deprotonated GP, [GP − H]⁻, generates FA anions, [FA − H]⁻. The fatty acid anions can then react with doubly charged cationic magnesium tris-phenanthroline complex, [Mg(Phen)₃]²⁺, to form charge inverted complex cations of the form [FA − H + MgPhen₂]⁺. CID of the complex generates product ion spectral patterns that allow for the identification of carbon–carbon double bond position(s) as well as the sites of cyclopropyl position(s) in unsaturated lipids. This approach to determining both double bond and cyclopropane positions is demonstrated with GPs for the first time using standards and is applied to lipids extracted from Escherichia coli.     

Fragmentation of the tryptophan cluster [Trp9-2H]2- induced by different activation methods

Electrospray ionization (ESI) of tryptophan gives rise to multiply charged, non‐covalent tryptophan cluster anions, [Trp_n–xH]^x?, in a linear ion trap mass spectrometer, as confirmed by high‐resolution experiments performed on a Fourier transform ion cyclotron resonance (FT‐ICR) mass spectrometer. The smallest multiply charged clusters that can be formed in the linear ion trap as a function of charge state are: x = 2, n = 7; x = 3, n = 16; x = 4, n = 31. The fragmentation of the dianionic cluster [Trp₉–2H]^2? was examined via low‐energy collision‐induced dissociation (CID), ultraviolet photodissociation (UVPD) at 266 nm and electron‐induced dissociation (EID) at electron energies ranging from >0 to 30 eV. CID proceeds mostly via charge separation and evaporation of neutral tryptophan. The smallest doubly charged cluster that can be formed via evaporation of neutral tryptophans is [Trp₇–2H]^2?, consistent with the observation of this cluster in the ESI mass spectrum. UVPD gives singly charged tryptophan clusters ranging from n = 2 to n = 9. The latter ion arises from ejection of an electron to give the radical anion cluster, [Trp₉–2H]^?.. The types of gas‐phase EID reactions observed are dependent on the energy of the electrons. Loss of neutral tryptophan is an important channel at lower energies, with the smallest doubly charged ion, [Trp₇–2H]^2?, being observed at 19.8 eV. Coulomb explosion starts to occur at 19.8 eV to form the singly charged cluster ions [Trp_x–H]^? (x = 1–8) via highly asymmetric fission. At 21.8 eV a small amount of [Trp₂–H–NH₃]^? is observed. Thus CID, UVPD and EID are complementary techniques for the study of the fragmentation reactions of cluster ions. Copyright © 2010 John Wiley & Sons, Ltd.     

Study of Cluster Anions Generated by Laser Ablation of Titanium Oxides: A High Resolution Approach Based on Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

Laser ablation of titanium oxides at 355 nm and ion–molecule reactions between [(TiO₂)_x]^–• cluster anions and H₂O or O₂ were investigated by Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS) with an external ion source. The detected anions correspond to [(TiO₂)_x(H₂O)_yOH]^– and [(TiO₂)_x(H₂O)_yO₂]^–• oxy-hydroxide species with x = 1 to 25 and y = 1, 2, or 3 and were formed by a two step process: (1) laser ablation, which leads to the formation of [(TiO₂)_x]^–• cluster anions as was previously reported, and (2) ion–molecule reactions during ion storage. Reactions of some [(TiO₂)_x]^–• cluster anions with water and dioxygen conducted in the FTICR cell confirm this assessment. Tandem mass spectrometry experiments were also performed in sustained off-resonance irradiation collision-induced dissociation (SORI-CID) mode. Three fragmentation pathways were observed: (1) elimination of water molecules, (2) O₂ loss for radical anions, and (3) fission of the cluster. Density functional theory (DFT) calculations were performed to explain the experimental data.     

Reactivity Control of C?H Bond Activation over Vanadium–Silver Bimetallic Oxide Cluster Cations

Vanadium–silver bimetallic oxide cluster ions (V_xAg_yO_z⁺; x=1–4, y=1–4, z=3–11) are produced by laser ablation and reacted with ethane in a fast‐flow reactor. A reflectron time of flight (Re‐TOF) mass spectrometer is used to detect the cluster distribution before and after the reactions. Hydrogen atom abstraction (HAA) reactions are identified over VAgO₃⁺, V₂Ag₂O₆⁺, V₂Ag₄O₇⁺, V₃AgO₈⁺, V₃Ag₃O₉⁺, and V₄Ag₂O₁₁⁺ ions, in which the oxygen‐centered radicals terminally bonded on V atoms are active sites for the facile HAA reactions. DFT calculations are performed to study the structures, bonding, and reactivity. The reaction mechanisms of V₂Ag₂O₆⁺+C₂H₆ are also given. The doped Ag atoms with a valence state of +1 are highly dispersed at the periphery of the V_xAg_yO_z⁺ cluster ions. The reactivity can be well‐tuned gradually by controlling the number of Ag atoms. The steric protection due to the peripherally bonded Ag atoms greatly enhances the selectivity of the V–Ag bimetallic oxide clusters with respect to the corresponding pure vanadium oxide systems.     

Diagnostic di‐ and triphosphate cyclisation in the negative ion electrospray mass spectra of phosphoSer peptides

It has been shown previously that [M–H]^– anions of small peptides containing two phosphate residues undergo cyclisation of the phosphate groups, following collision‐induced dissociation (CID), to form a characteristic singly charged anion A (H₃P₂O₇^–, m/z 177). In the present study it is shown that the precursor anions derived from the diphosphopeptides of caerin 1.1 [GLLSVLGSVAKHVLPHVVPVIAEHL(NH₂)] and frenatin 3 [GLMSVLGHAVGNVLGGLFKPKS(OH)] also form the characteristic product anion A (m/z 177). Both of the precursor peptides show random structures in water, but partial helices in membrane‐mimicking solvents [e.g. in d₃‐trifluoroethanol/water (1:1)]. In both cases the diphosphopeptide precursor anions must have flexible conformations in order to allow approach of the phosphate groups with consequent formation of A: for example, the two pSer groups of 4,22‐diphosphofrenatin 3 are seventeen residues apart. Finally, CID tandem mass spectrometric (MS/MS) data from the [M–H]^– anion of the model triphosphoSer‐containing peptide GpSGLGpSGLGpSGL(OH) show the presence of both product anions A (m/z 177) and D (m/z 257, H₄P₃O₁₀^–). Ab initio calculations at the HF/6‐31+G(d)//AM1 level of theory suggest that cyclisation of the three phosphate groups occurs by a stepwise cascade mechanism in an energetically favourable reaction (ΔG = ?245 kJ mol^–1) with a maximum barrier of +123 kJ mol^–1. Copyright © 2011 John Wiley & Sons, Ltd.     

Vanadium oxide anion cluster reactions with methyl isobutyrate and methyl methacrylate monomer and dimer: a study by FT/ICR mass spectrometry

Laser ablation of vanadium pentoxide (V₂O₅) powder produces VO₃⁻, V₂O₅⁻, V₃O₇⁻, V₃O₈⁻, and V₄O₁₀⁻ cluster ions which have subsequently been reacted with methyl isobutyrate, methyl methacrylate monomer and its dimer in the ion cell region of a Fourier transform ion cyclotron resonance mass spectrometer. Gas phase ion/molecule chemistry has revealed that reactivity decreases with increased mass of the vanadium oxide cluster anions. VO₃⁻, V₂O₅⁻, and V₃O₇⁻ ions react with the three reagents, methyl isobutyrate, methyl methacrylate and its dimer, respectively, either by addition of a whole reagent molecule or an associated fragment. All products formed are a result of parallel processes. V₄O₁₀⁻ undergoes no reaction for reaction times of up to 500 s, while V₃O₈⁻ adds a water molecule. Although the ions possess a net negative charge, the reactive site toward electron rich reagents such as methyl isobutyrate, methyl methacrylate and its dimer is the under-coordinated vanadium atom. This observation is supported by the lack of reactivity toward the studied reagents by those anions (V₃O₈⁻ and V₄O₁₀⁻) whose most likely stable structures contain fully coordinated vanadium atoms.     

Gas‐Phase Reaction of CeV2O7+ with C2H4: Activation of CC and CH Bonds

The reactivity of metal oxide clusters toward hydrocarbon molecules can be changed, tuned, or controlled by doping. Cerium‐doped vanadium cluster cations CeV₂O₇⁺ are generated by laser ablation, mass‐selected by a quadrupole mass filter, and then reacted with C₂H₄ in a linear ion trap reactor. The reaction is characterized by a reflectron time‐of‐flight mass spectrometer. Three types of reaction channels are observed: 1) single oxygen‐atom transfer , 2) double oxygen‐atom transfer , and 3) C?C bond cleavage. This study provides the first bimetallic oxide cluster ion, CeV₂O₇⁺, which gives rise to C?C bond cleavage of ethene. Neither Ce_xO_y^± nor V_xO_y^± alone possess the necessary topological and electronic properties to bring about such a reaction.     

Phase formation in the system Zn(VO<Subscript>3</Subscript>)<Subscript>2</Subscript>–HCl–VOCl<Subscript>2</Subscript>–H<Subscript>2</Subscript>O

The phase and chemical compositions of precipitates formed in the system Zn(VO₃)₂–HCl–VOCl₂–H₂O at pH 1?3, molar ratio V⁴⁺: V⁵⁺ = 0.1?9, and 80°C were studied. It was shown that, within the range 0.4 ≤ V⁴⁺: V⁵⁺ ≤ 9, zinc vanadate with vanadium in a mixed oxidation state forms with the general formula Zn_xV⁴⁺ _yV⁵⁺ _2-yO₅ ? nH₂O (0.005 ≤ x ≤ 0.1, 0.05 ≤ y ≤ 0.3, n = 0.5?1.2). Vanadate Zn_xV₂O₅ ? nH₂O with the maximum tetravalent vanadium content (y = 0.30) was produced within the ratio range V⁴⁺: V⁵⁺ = 1.5?9.0. Investigation of the kinetics of the formation of Zn_xV₂O₅ ? nH₂O at pH 3 determined that tetravalent vanadium ions VO2+ activate the formation of zinc vanadate, and its precipitation is described by a second-order reaction. It was demonstrated that, under hydrothermal conditions at pH 3 and 180°C, zinc decavanadate in the presence of VOCl₂ can be used as a precursor for producing V₃O₇ ? H₂O nanorods 50–100 nm in diameter.     

C−−H activation on aluminum-vanadium bimetallic oxide cluster anions

Aluminum–vanadium bimetallic oxide cluster anions (BMOCAs) have been prepared by laser ablation and reacted with ethane and n‐butane in a fast‐flow reactor. A time‐of‐flight mass spectrometer was used to detect the cluster distribution before and after the reactions. The observation of hydrogen‐containing products AlVO₅H^? and Al_xV_4?xO_11?xH^? (x=1–3) strongly suggests that AlVO₅^? and Al_xV_4?xO_11?x^? (x=1–3) can react with ethane and n‐butane by means of an oxidative dehydrogenation process at room temperature. Density functional theory studies have been carried out to investigate the structural, bonding, electronic, and reactive properties of these BMOCAs. Terminal‐oxygen‐centered radicals (O_t^.) were found in all of the reactive clusters, and the O_t^. atoms, which prefer to be bonded with Al rather than V atoms, are the active sites of these clusters. All the hydrogen‐abstraction reactions are favorable both thermodynamically and kinetically. To the best of our knowledge, this is the first example of hydrogen‐atom abstraction by BMOCAs and may shed light on understanding the mechanisms of C? H activation on the surface of alumina‐supported vanadia catalysts.     

Electrospray mass and tandem mass spectrometry of homologous and isomeric singly, doubly, triply and quadruply charged cationic ruthenated meso-(phenyl)m-(meta- and para-pyridyl)n (m + n = 4) macrocyclic porphyrin complexes

Ten homologous or isomeric singly, doubly, triply and quadruply charged cationic macrocyclic complexes I-Va, bn+ (n = 1-4) formed by the coordination of [Ru(bipy)2Cl]+ to the pyridyl N-atoms of a series of meso-(phenyl)m-(meta or para-pyridyl)n-porphyrins (m + n = 4) were transferred to the gas phase and structurally characterized by electrospray ionization (ESI) mass (MS) and tandem mass (MS/MS) spectrometry. Previously known to be stable in solution and in the solid state, I-Va, bn+ are found to constitute also a new class of stable, long-lived multiply charged gas-phase ions with spatially separated charge sites. Increasing intramolecular electrostatic repulsion from Ia, b+ to IVa, b3+ facilitates in-source and tandem collision-induced dissociation (CID). However, for the quadruply charged ions Va, b4+, electrostatic repulsion is alleviated mainly by ion pairing with the CF3SO3- counterion forming the salt clusters [Va,b/CF3SO3]3+ and [Va,b/(CF3SO3)2]2+ with reduced charge states. Ion-pairing that yields [IVa,b/CF3SO3]2+ is also observed as a minor ESI process for the triply charged ions IVa, b3+. The gaseous ions I-Va, bn+ (n = 2, 3 or 4) dissociate by sequential 'charge partitioning' with the formation of two cationic fragments by the release of [Ru(bipy)2Cl]+. The meta (a) and para (b) isomers and the positional isomers II2+ and III2+ display nearly identical ESI-MS and ESI-MS/MS spectra. ESI-MS/MS of I-Va, bn+ shows that the Ru-py(P) is, intrinsically, the weakest bond since this bond breaks preferentially upon CID.     

Ligand size distribution of phenanthroline-functionalized polyethylene glycol-iron(II) complexes determined by electrospray ionization mass spectrometry and computer simulation

The complex formation in solution, and the gas-phase dissociation of a phenanthrolineterminated poly(ethylene glycol) with Fe²⁺ ions were investigated. The size distribution of poly(ethylene glycol)-α-monomethyl-ω-5-[1,10]phenanthroline (mPEG_phen) was determined by electrospray ionization mass spectrometry (ESI-MS). Based on the measured ligand size distribution of mPEG_phen by ESI-MS, the 1:3 complex formation (Fe²⁺/mPEG_Phen) was computer-simulated as a pure random assembly process. The simulated distribution fits excellently to that of the complex Fe(mPEG_phen)₃²⁺ determined from the ESI-MS intensities. In addition, the collision-induced dissociation (CID) of the Fe(mPEG_phen)₃²⁺ complex was also studied by tandem mass spectrometry (ESI-MS/MS) and by computer simulation, as well. The ESI-MS/MS intensity distribution of the Fe(mPEG_phen)₂²⁺ formed from Fe(mPEG_phen)₃²⁺ by the loss of an mPEG_phen ligand under CID conditions fits quite well to the calculated one.     

Classification of VxOyq Clusters by △=2y+q-5x

Vanadium oxide clusters V_xO_y^q (x≤8, q=0,±1) are classified according to the oxidation index (△=2y+q-5x) of each cluster. Density functional calculations indicate that clusters with the same oxidation index tend to have similar bonding characters, electronic structures, and reactivities. This general rule leads to the findings of new possible ground state struc-tures for V₂O₆ and V₃O₆⁺ clusters. This successful application of the classification method on vanadium oxide clusters proves that this method is very effective in studying the bonding properties of early transition metal oxide clusters.     

Comparison of collision‐ versus electron‐induced dissociation of sodium chloride cluster cations

The collision‐induced dissociation (CID) and electron‐induced dissociation (EID) spectra of the [(NaCl)_m(Na)_n]ⁿ⁺ clusters of sodium chloride have been examined in a hybrid linear ion trap Fourier transform ion cyclotron resonance mass spectrometer. For singly charged cluster ions (n = 1), mass spectra for CID and EID of the precursor exhibit clear differences, which become more pronounced for the larger cluster ions. Whereas CID yields fewer product ions, EID produces all possible [(NaCl)_xNa]⁺ product ions. In the case of doubly charged cluster ions, EID again leads to a larger variety of product ions. In addition, doubly charged product ions have been observed due to loss of neutral NaCl unit(s). For example, EID of [(NaCl)₁₁(Na)₂]²⁺ leads to formation of [(NaCl)₁₀(Na)₂]²⁺, which appears to be the smallest doubly charged cluster of sodium chloride observed experimentally to date. The most abundant product ions in EID spectra are predominantly magic number cluster ions. Finally, [(NaCl)_m(Na)₂]^{+ .} radical cations, formed via capture of low‐energy electrons, fragment via the loss of [(NaCl)_n(Na)] ^. radical neutrals. Copyright © 2008 John Wiley & Sons, Ltd.     

Investigation on C2-ceramide complexes with transition metal ions using electrospray ionization tandem mass spectrometry

Electrospray ionization-tandem mass spectrometry (ESI-MS/MS) is applied for the investigation of C(2)-ceramide complexes with transition metal ions. Ceramide plays an important role in the regulation of various signaling pathways leading to proliferation, differentiation or apoptotic cell death. The formation and fragmentation of doubly charged cluster ions as well as singly charged cluster ions of C(2)-ceramide with transition metal ions (Mn(2+), Fe(2+), Co(2+) and Ni(2+)) are studied by ESI-MS/MS in the positive mode. Tube lens offset voltage and concentrations of C(2)-ceramide and transition metals are optimized to determine the best conditions for generating doubly charged cluster ions. The fragmentation pathways of metal ion complexes with C(2)-ceramide and the compositions of these complexes are determined by collision induced dissociation (CID). All transition metal ions (Mn(2+), Fe(2+), Co(2+) and Ni(2+) except Cu(2+)) shows similar complexation with C(2) ceramide. The unique complexation behavior of copper(II) is responsible for the different geometry of the complexes and relatively lower affinity of ceramide to copper(II) than those to other transition metals.     

Rapid method for quantifying the extent of methionine oxidation in intact calmodulin

We have developed a method for rapidly quantifying the extent to which the functionally important Met¹⁴⁴ and Met¹⁴⁵ residues near the C-terminus of calmodulin (CaM) are converted to the corresponding sulfoxides, Met(O). The method utilizes a whole protein collision-induced dissociation (CID) approach on an electrospray ionization quadrupole time-of-flight (ESI-Q-TOF) mass spectrometer. Using standards of CaM oxidized by hydrogen peroxide (H₂O₂) or peroxynitrite (ONOO⁻), we demonstrated that CID fragmentation of the protein ions resulted in a series of C-terminal singly charged y₁–y₁₅ ions. Fragments larger than y₄ exhibited mass shifts of +16 or +32 Da, corresponding to oxidation of one or two methionines, respectively. To assess the extent of oxidative modification for Met¹⁴⁴ and Met¹⁴⁵ to Met(O), we averaged the ratio of intensities for y _n , y _n + 16, and y _n + 32 ions, where n = 6–9. By alternating MS and CID scans at low and high collision energies, this technique allowed us to rapidly determine both the distribution of intact CaM oxiforms and the extent of oxidative modification in the C-terminal region of the protein in a single run. We have applied the method to studies of the repair of fully oxidized CaM by methionine sulfoxide reductases (MsrA and MsrB), which normally function in concert to reduce the S and R stereoisomers of methionine sulfoxide. We found that repair of Met(O)¹⁴⁴ and Met(O)¹⁴⁵ did not go to completion, but was more efficient than average Met repair. Absence of complete repair is consistent with previous studies showing that accumulation of methionine sulfoxide in CaM can occur during aging (Gao, J.; Yin, D.; Yao, Y.; Williams, T. D.; Squier, T. C. Biochemistry 1998, 37, 9536–9548).     

A Novel Expansion Mode of Polyoxovanadate Clusters: Synthesis,Crystal Structure and Properties of {[Cu(H2O)(C5H14N2)2]2[V16O38(Cl)]}·4(C5H16N2)

The new polyoxovanadate (POV) compound {[Cu(H₂O)(C₅H₁₄N₂)₂]₂[V₁₆O₃₈(Cl)]} · 4(C₅H₁₆N₂) was synthesized under solvothermal conditions and crystallizes in the tetragonal space group I4₁/amd with a = 13.8679(6), c = 45.558(2) Å, V = 8761.7(7) ų. The central structural motif is a {V₁₆O₃₈(Cl)} cluster constructed by condensation of 16 square‐pyramidal VO₅ polyhedra. The cluster hosts a central Cl^– anion. According to valence bond sum calculations, chemical analysis and magnetic properties the cluster anion may be formulated as [V₁₅^IVV^VO₃₈(Cl)]^12–, i.e., only one vanadium atom is not reduced. To the best of our knowledge this is the first reported {V₁₆O₃₈(X)} cluster in this V^IV:V^V ratio. The presence of the two different vanadium oxidation states is clearly seen in the IR spectrum. An unusual and hitherto never observed structural feature is the binding mode between the [Cu(H₂O)(C₅H₁₄N₂)₂]²⁺ complexes and the [V₁₅^IVV^VO₃₈(Cl)]^12– anion. The Cu²⁺ ion binds to a μ₂‐O atom of the cluster anion whereas in all other transition metal complex‐augmented POVs bonding between the transition metal cation and the anion occurs through terminal oxygen atoms of the POV. The magnetic properties are dominated by strong antiferromagnetic exchange interactions between the V⁴⁺ d¹ centers, whereas the Cu²⁺ d⁹ cations are magnetically decoupled from the cluster anion. Upon heating, the title compound decomposes in a complex fashion.     

Electrochemical study of isopoly and heteropoly anion transfer across the water | nitrobenzene interface. Part II. Vanadium-containing heteropolytungstate anions

The electrochemical transfer behaviour of vanadium-containing heteropolytungstate anions [PW_12−xV_xO₄₀]^(3+x)− (x = 1−4) across the water | nitrobenzene interface has been investigated by cyclic voltammetry and chronopotentiometry with cyclic linear current scanning. The transfer of PW₁₁V₁O⁴⁻₄₀, HPW₁₀V₂O⁴⁻₄₀, H₂PW₁₀V₂O³⁻₄₀, H₃PW₉V₃O³⁻₄₀ and H₄PW₈V₄O³⁻₄₀ across the water | nitrobenzene interface can be observed within the potential window. The effects were observed of pH in the water phase on the transfer behaviour and the formation of vanadium-containing heteropolytungstate anions in solution. Heteropolytungstate anions become more stable due to their involving the vanadium atom. The degree of protonation and the dissociation constant of the trivalent vanadium-containing heteropolytungstate anion of protonation increase with increasing vanadium content. The transfer processes are diffusion-controlled. The standard transfer potential, the standard Gibbs energy and the dissociation constant for vanadium-containing heteropolytungstate anions have been obtained and the transfer mechanisms are discussed.     

An isomer-specific high-energy collision-induced dissociation MS/MS database for forensic applications: a proof-of-concept on chemical warfare agent markers

Spectra database search has become the most popular technique for the identification of unknown chemicals, minimizing the need for authentic reference chemicals. In the present study, an isomer‐specific high‐energy collision‐induced dissociation (CID) MS/MS spectra database of 12 isomeric O‐hexyl methylphosphonic acids (degradation markers of nerve agents) was created. Phosphonate anions were produced by the electrospray ionization of phosphonic acids or negative‐ion chemical ionization of their fluorinated derivatives and were analysed in a hybrid magnetic‐sector–time‐of‐flight tandem mass spectrometer. A centre‐of‐mass energy (E_com) of 65 eV led to an optimal sequential carbon–carbon bond breakage, which was interpreted in terms of charge remote fragmentation. The proposed mechanism is discussed in comparison with the routinely used low‐energy CID MS/MS. Even‐mass (odd‐electron) charge remote fragmentation ion series were diagnostic of the O‐alkyl chain structure and can be used to interpret unknown spectra. Together with the odd‐mass ion series, they formed highly reproducible, isomer‐specific spectra that gave significantly higher database matches and probability factors (by 1.5 times) than did the EI MS spectra of the trimethylsilyl derivatives of the same isomers. In addition, ionization by negative‐ion chemical ionization and electrospray ionization resulted in similar spectra, which further highlights the general potential of the high‐energy CID MS/MS technique. Copyright © 2011 John Wiley & Sons, Ltd.     

Electrochemical properties and state of paramagnetic centers in copper-modified complex vanadium and titanium oxides

Complex vanadium and titanium oxides modified by copper ions are studied by the electrochemical and ESR methods. Oxides Cu _x V_2?y Ti _y O_5?δ·nH₂O (0<y<1.33) have a layered structure and oxides Cu _x Ti_1?y V _y O_5+δ·nH₂O (0<y<0.25), an anatase structure. The intercalation of cations Cu²⁺ into the hydrates leads to oxidation of V⁴⁺. According to ESR data, V⁴⁺ exists in the oxides in the form of VO²⁺ and an octahedral surround of oxygen (V⁴⁺?O₆), respectively. The electroreduction of ions of d-elements and chemisorbed oxygen in the oxides is analyzed. The intercalation of cations Cu²⁺ alters the content of V⁴⁺ and the chemisorption ability of the oxides. Possible reasons for this phenomenon are discussed.     

Analysis of a stacked-triangular platinum carbonyl cluster dianion, [Pt3(CO)6] 3 2− by252Cf-Plasma Desorption Mass Spectrometry

²⁵²Cf-Plasma Desorption Mass Spectrometry (²⁵²Cf-PDMS) has been used to investigate the [(Ph₃PCH₂C₅H₄)Fe(C₅H₅)]⁺ salt of the prototype dianionic, platinum carbonyl cluster, [Pt₃(CO)₃(₂-CO)₃] ₃ ^2– . An envelope of singly charged [Pt₉(CO) _x ]^– ions with the principal peak centered atx=8 was observed in the negative ion mass spectrum as a result of successive losses of the carbonyl ligands from the intact platinum core. Another feature of the negative ion spectrum was the prominent occurrence of other envelopes of multiple peaks which conform to Pt₁₂, Pt₁₅, Pt₁₈, Pt₂₁, and Pt₂₄ singly charged metal cores. An unexpected observation was the presence of singly charged positive ions of the dianionic cluster which were formed without incorporation of the counterion. A similar but, largely unresolvable, broad envelope of singly charged ions containing the Pt₉ core resulted with a peak maximum corresponding closely to the completely carbonylated cluster. The peak distribution extended from the fully decarbonylated cluster to well beyond the mass of the fully carbonylated cluster. Analogous peaks attributable to singly charged positive ions of the Pt₁₂, Pt₁₅, and Pt₁₈ clusters were also evident. Very little fragmentation was observed below the molecular ion in either the positive or negative ion mass spectra except for ions associated with the counterion. A detailed analysis of the mass spectra, including the types of ions observed and correlations with the molecular architecture are described.