Field Desorption Mass Spectra Research Articles

ChemInform Abstract: Reinvestigation of Synthetic Methods for Zinc meso- Tetraphenyltetrabenzoporphyrin.

Abstract The reaction of 3-benzylidenephthalimidine (3-BPI) with zinc acetate for the preparation of the meso- tetraphenyltetrabenzoporphyrin zinc complex (ZnP4TBP) is reinvestigated. From the structural analyses of the reaction product with ultraviolet-visible absorption spectra, field desorption mass spectra (FDMS) and 1H NMR spectra, it is shown that this reaction procedure gives a complicated mixture of ZnTBP derivatives with meso-phenyl substituent(s) the number of which is from one to four. The product obtained by the reaction of isoindole with benzaldehyde in the presence of zinc acetate is also discussed.

Development of a new electron ionization/field ionization ion source for gas chromatography/time‐of‐flight mass spectrometry

We have developed a combined EI/FI source for gas chromatography/orthogonal acceleration time-of-flight mass spectrometry (GC/oaTOFMS). In general, EI (electron ionization) and FI (field ionization) mass spectra are complementary: the EI mass spectrum contains information about fragment ions, while the FI mass spectrum contains information about molecular ions. Thus, the comparative study of EI and FI mass spectra is useful for GC/MS analyses. Unlike the conventional ion sources for FI and EI measurements, the newly developed source can be used for both measurements without breaking the ion source vacuum or changing the ion source. Therefore, the combined EI/FI source is more preferable than the conventional EI or FI ion source from the viewpoint of the reliability of measurements and facility of operation. Using the combined EI/FI source, the complementarity between EI and FI mass spectra is demonstrated experimentally with n-hexadecane (100 pg): characteristic fragment ions for the n-alkane such as m/z 43, 57, 71, and 85 are obtained in the EI mass spectrum, while only the parent peak of m/z 226 (M+) without any fragment ions is observed in the FI mass spectrum. Moreover, the field desorption (FD) measurement is also demonstrated with poly(ethylene glycol)s M600 (10 ng) and M1000 (15 ng). Signals of [M+H]+, [M+Na]+ and [M+K]+ are clearly detected in the FD mass spectra.

Metal complexes derived from hydrazoneoxime ligands: IV. Molecular and supramolecular structures of some nickel(II) complexes derived from diacetylmonoxime S-benzyldithiocarbazonate

Four new nickel(II) complexes, [{Ni(L)} 2], [NiL · HPyr], [NiL · HIm] and [Ni(HL) 2] · H 2O, derived from diacetylmonoxime- S-benzyldithiocarbazonate (H 2L) have been synthesized and characterized by elemental analyses, field desorption and electrospray ionization mass spectra, UV–Vis, infrared absorption spectra, as well as 1H NMR spectra. X-ray molecular structures showed that the Ni(II) in both [NiL · HPyr] and [NiL · HIm] are in a distorted square planar environment and is coordinated to the dianionic NNS tridentate hydrazoneoxime ligand via deprotonated oximate nitrogen, hydrazone imine nitrogen, and thiolate sulphur. The fourth coordination sites are occupied, respectively, by the pyrazole and imidazole nitrogens. The oximate O1 of [NiL · HPyr] is involved in intramolecular hydrogen bond with the pyrazole NH proton as well as intermolecular hydrogen bond pyrazole C6H proton, forming a helical chain propagating along the b-axis. The structure is stabilized by a set of π⋯π and CH⋯π interactions. The molecular units in [NiL · HIm] are linked together by hydrogen bond formation between the oximate oxygen and imidazole NH proton, giving rise to an infinite zigzag chain extended along the a-axis. The chains are interconnected by π⋯π and CH⋯O interactions. In [Ni(HL) 2] · H 2O, the Ni(II) is in a distorted octahedral environment. The two mononegative hydrazoneoxime ligands are coordinated in the meridional configuration where the two thiol sulphur atoms and the two oxime nitrogen atoms are cis to each other, while the imine nitrogen atoms are trans. The oxime proton O2H is involved in a reciprocal bifurcated hydrogen bond formation with both N2 and S3 of the adjacent molecule giving rise to hydrogen bonded dimer. This dimeric structure is further stabilized by a pair of reciprocal CH⋯O interactions. A one dimensional chain of alternating dimeric unit and water molecule propagating along the c-axis is formed via hydrogen bond formation between the oxime O1 oxygen and the bridged water molecule proton.

ガスクロマトグラフィー／飛行時間型質量分析法を用いた原油・石油製品のタイプ分析

Type analysis of crude oil and petroleum products has been studied using a gas chromatograph/time-of-flight mass spectrometer. The use of inert fused silica capillary tube inlet/field ionization (blank tube inlet/FI) is a suitable method for analyzing low boiling point components. Field ionization (FI) and field desorption (FD) methods are classified as soft ionization. Therefore, those ionization methods are used to analyze samples in which the molecular ion is hardly detected on electron ionization, as in the case of hydrocarbons. Type analysis using blank tube inlet/FI, capillary gas chromatography/FI (GC/FI), and FD mass spectra provides useful information, such as the average molecular weight. We examined the composition of crude oil and some petroleum products by type analysis using blank tube inlet/FI, capillary GC/FI, and FD. We carried out type analysis using six series of components. These were CnH2n+2, CnH2n, CnH2n-2, CnHn-4, CnHn-6, and CnHn-8. The averaged molecular weight by FD was much higher than that by blank tube inlet/FI, because it is difficult to measure low boiling point components by FD. In the blank tube inlet/FI method, all components were introduced and ionized. Therefore, this method is much more suitable than other methods for evaluating the composition of crude oil and petroleum products.

Oxygen adsorption on gold nanofacets and model clusters

We have studied oxygen interaction with Au crystals (field emitter tips) using time-resolved (atom-probe) field desorption mass spectrometry. The results demonstrate no adsorption to take place on clean Au facets under chosen conditions of pressures (p < 10(-4) m/bar) and temperatures (T = 300-350 K). Steady electric fields of 6 V/nm do not allow dissociating the oxygen molecule. The measured O2+ intensities rather reflect ionization of O2 molecules at critical distances above the Au tip surface. Certain amounts of Au-O2 complex ions can be found at the onset of Au field evaporation. Calculations by density functional theory (DFT) show weak oxygen end-on interaction with Au10 clusters (Delta E = 0.023 eV) and comparatively stronger interaction with Au1/Au(100) model surfaces (Delta E = 0.25 eV). No binding is found on {210} facets. Including (positive) electric fields in the DFT calculations leads to an increase of the activation energy for oxygen dissociation thus providing an explanation for the absence of atomic oxygen ions from the field desorption mass spectra.

Synthesis of well‐defined syndiotactic poly(methyl methacrylate) with low‐temperature atom transfer radical polymerization in fluoroalcohol

AbstractThe copper‐mediated atom transfer radical polymerization of methyl methacrylate (MMA) in 1,1,1,3,3,3‐hexafluoro‐2‐propanol (HFIP) was studied to simultaneously control the molecular weight and tacticity. The polymerization using tris[2‐(dimethylamino)ethyl]amine (Me6TREN) as a ligand was performed even at −78°C with a number‐average molecular weight (Mn) of 13,400 and a polydispersity (weight‐average molecular weight/number‐average molecular weight) of 1.31, although the measured Mn's were much higher than the theoretical ones. The addition of copper(II) bromide (CuBr2) apparently affected the early stage of the polymerization; that is, the polymerization could proceed in a controlled manner under the condition of [MMA]0/[methyl α‐bromoisobutyrate]0/[CuBr]0/[CuBr2]0/[Me6TREN]0 = 200/1/1/0.2/1.2 at −20°C with an MMA/HFIP ratio of 1/4 (v/v). For the field desorption mass spectrum of CuIBr/Me6TREN in HFIP, there were [Cu(Me6TREN)Br]+ and [Cu(Me6TREN)OCH(CF3)2]+, indicating that HFIP should coordinate to the CuI/Me6TREN complex. The syndiotacticity of the obtained poly(methyl methacrylate)s increased with the decreasing polymerization temperature; the racemo content was 84% for −78°C, 77% for −30°C, 75% for −20°C, and 63% for 30°C. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1436–1446, 2006

Synthesis, characterization and magnetochemical studies of some copper(II) complexes derived from n-salicylidene- n-alkanoylhydrazins: X-ray crystal and molecular structure of bis [monochloro-(μ- n-salicylidenemyristoylhydrazine)ono(−1)] dicopper(II)

Three types of copper(II) complexes, [Cu(HL)Cl · H 2O] · xH 2O, [{Cu(HL)Cl} 2] and [{Cu(L)} 2], derived from N-Salicylidene- n-alkanoylhydrazines (H 2L) have been synthesized and characterized by elemental analyses, infrared spectra and field desorption mass spectra as well as variable temperature magnetic susceptibility measurements. The X-ray molecular structure of bis[monochloro(μ- N-salicylidene myristoylhydrazine)ONO ′(−1)]dicopper(II) showed that this complex is a centrosymmetric dimer in which each copper(II) is in a distorted square pyramidal environment and coordinated in the equatorial plane to the ONO mononegative tridentate acylhydrazone ligand. The fourth coordination site is occupied by the symmetry related phenoxy oxygen of the other monomeric unit. The chloride ion occupies the fifth axial coordination site. Magnetic susceptibility measurements at different temperatures (5–298 K) showed that the hydrated chloro complexes [Cu(HL)Cl · H 2O] · xH 2O are monomeric and no spin–spin interaction was detected, while the anhydrous chloro complexes [{Cu(HL)Cl} 2] are dimeric and exhibit strong antiferromagnetic coupling with −2 J values the range 466–477 cm −1. The neutral complexes [{Cu(L)} 2] also show antiferromagetic behaviour with −2 J varying from 170 to 243 cm −1.

Sugar hydrazone–metal complexes: transition- and non-transition metal complexes of monosaccharide S-alkylhydrazonecarbodithioates and dehydro- l-ascorbic acid bis( S-alkylhydrazonecarbodithioates)

Copper(II), nickel(II) and palladium(II) complexes with aldehydo- d-arabinose-, l-arabinose-, d-galactose-, d-glucose- and d-mannose- S-methyl- and S-benzylhydrazonecarbodithioates were synthesized and characterized by elemental analyses, infrared and UV–Vis. In these complexes the aldehydo sugar hydrazone acts as a mononegative NS bidentate ligand. The reaction of Cu(II) chloride, however, proceeded with reduction, and copper(I) complexes were isolated. The hydrazone molecule in these Cu(I) complexes acts as neutral NS bidentate ligand. Dehydro- l-ascorbic acid bis( S-methylhydrazinecarbodithioate) and bis(hydrazinecarbothioamide), as well as their corresponding Cu(II), Ni(II), zinc(II) and Pd(II) complexes were prepared and characterized. Electrospray (ES) and field desorption (FD) mass spectra suggest that the Cu(II), Ni(II), and Pd(II) complexes are monomeric (square planar), whereas the Zn(II) are dimeric and pentacoordinate.

Polymerization of Bisphenol A by Purified Laccase from Trametes villosa

The metabolism of bisphenol A (BPA), an endocrine-disrupting chemical, was studied with a highly purified laccase from the basidiomycete Trametes villosa. The enzyme reaction products ranged widely from water-insoluble to -soluble compounds, one of which was previously identified as 4-isopropenylphenol. 1H NMR and electron-impact mass spectrum analyses showed that one of the insoluble products was a BPA dimer, 5,5′-bis-[1-(4-hydroxy-phenyl)-1-methyl-ethyl]-biphenyl-2,2′-diol. Field-desorption mass spectrum analysis revealed BPA oligomers, some of which contained phenol, within the insoluble fraction. These results indicate that the laccase reaction may contain successive BPA polymerization, followed by either the addition of phenol to the formed oligomers or their decomposition to release 4-isopropenylphenol.

Volatile β-diketonato Complexes of Ruthenium, Palladium and Platinum. Preparation and Thermal Characterization

Ruthenium, palladium and platinum complexes of 2,2,6,6-tetramethyl-3,5-heptanedione (thd) and ruthenium tris acetylacetonate (acac) were synthetized and studied with TG, DTA, DSC and MS methods. Thermal properties of ruthenocene were also studied. The platinum thd complex has the highest volatility despite the second highest molecular mass of the complex. All the complexes sublimed under reduced pressure. Ru(acac)3 decomposed during sublimation under atmospheric pressure of nitrogen whereas the other compounds studied sublimed also under these conditions. Pd(thd)2 reduced under atmospheric pressure of H2 /N2 (5% H2 ) whereas the ruthenium complexes were not reduced. The field desorption mass spectra of complexes showed only the molecular peaks and no fragmentation occurred.

Zirconium Cage-Doped Fullerenes

Some zirconium containing fullerenes were synthesized by vaporizing a zirconium-containing graphite anode with DC arc discharge technique, extracted by CS2 through low temperature extraction method, and characterized by field desorption mass spectra (FDMS). The results show that these doped fullerenes were zirconium cage-doped fullerenes.

Macrocyclization of alpha-(alkynyloxy)silyl-alpha-diazoacetates by inter-/intramolecular

Thermally induced intra-/intermolecular [3 + 2] cycloaddition reaction sequences of alpha-(alkynyloxy)silyl-alpha-diazoacetates 1 lead to [3.3](1,4)pyrazolophanes (2)2 and higher cyclooligomers thereof [(2)n, n > 2]. In most cases, the cyclodimer was isolated by crystallization, while a complete separation of the mixture of the higher cyclooligomers was not possible. Solid state structures of cyclodimers (2b)2 and (2c)2, cyclotrimer (2b)3, and cyclotetramer (2e)4 were determined by X-ray diffraction analysis. Field-desorption mass spectra were used to characterize the cyclooligomer mixtures. The relative amounts of the cyclooligomers depend on the substitution pattern of the diazo compound. The cyclooligomerization reactions reported herein demonstrate, for the first time, the involvement of diazo functions in macrocyclization reactions via 1,3-dipolar cycloaddition.

Macrocyclization of α-(Alkynyloxy)silyl-α-diazoacetates by Inter-/Intramolecular [3+2] Cycloaddition Reaction Sequences

Thermally induced intra-/intermolecular [3+2] cycloaddition reaction sequences of α-(alkynyloxy)silyl-α-diazoacetates 1 lead to [3.3](1, 4/pyrazolophanes (2)2 and higher cyclooligomers thereof [(2)n, n>2]. In most cases, the cyclodimer was isolated by crystallization, while a complete separation of the mixture of the higher cyclooligomers was not possible. Solid state structures of cyclodimers (2 b)2 and (2 c)2, cyclotrimer (2 b)3, and cyclotetramer (2 e)4 were determined by X-ray diffraction analysis. Field-desorption mass spectra were used to characterize the cyclooligomer mixtures. The relative amounts of the cyclooligomers depend on the substitution pattern of the diazo compound. The cyclooligomerization reactions reported herein demonstrate, for the first time, the involvement of diazo functions in macrocyclization reactions via 1,3-dipolar cycloaddition.

Influence of Electric Field Strength and Emitter Temperature on Dehydrogenation and C—C Cleavage in Field Desorption Mass Spectrometry of Polyethylene Oligomers

The influence of electric field strength and emitter temperature on dehydrogenation and C–C cleavage in field desorption (FD) mass spectrometry of polyethylene (PE) oligomers of average molecular weights ranging from 500 to 2000 is examined. Low mass oligomers yield molecular weight (MW) distributions that are basically in accordance with results from gel-permeation chromatography. For these materials, dehydrogenation can be greatly reduced by reduction of the emitter potential. Furthermore, the influence of emitter potential on MW distributions indicates the occurrence of field-induced C–C cleavages. Reliable MW distributions are more difficult to obtain from higher mass oligomers by FD-MS because of the need for higher field strength and higher emitter temperatures to effect their desorption/ionization. Experiments reveal that the application of FD-MS to PE oligomers is limited not only by field-induced but also by thermally-induced fragmentations. Even then, FD mass spectra contain valuable information on mass range and homogeneity of PE samples up to about m/z 3600.

High-pressure synthesis of cyclic mesitylacetylene oligomer

Reaction of mesitylacetylene was carried out by annealing under high pressure (0.13 and 0.52 GPa). The products obtained were classified into soluble and insoluble products in chloroform. The insoluble product reacted under 0.13 GPa was the mesitylacetylene polymer. The soluble product reacted under 0.13 GPa was classified as the monomer and the oligomer [number-average molecular weight (M n ): 390, weight-average molecular weight (M w ): 453, Oligomer yield (O y ): 36%]. The oligomer yield was accelerated by pressure [pressure: 0.13-0.52 GPa, M n : 390-315, M w : 453-968, O y : 36-98%]. Field desorption mass spectrum showed that the oligomer had cyclic structure. The result of the elementary analysis revealed that the insoluble product reacted under 0.52 GPa was a polycyclic aromatic compound.

Synthesis of Silicon-containing Fullerenes

Abstract Macroscopic quantities of silicon-containing fullerenes have been synthesized by vaporizing a SiC-doped anode with DC arc discharge technique, extracted by CS2, and characterized by field desorption mass spectra (FDMS). Besides silicon-cage-doped fullerenes, in the extract some others which are supposed to be silicon endohedral fullerenes are also found.

Synthesis of C60-NBN and C70-NBN(N=L, 2) by DC arc Burning Method

Macroscopic quantities of boron-doped fullerenes, such as C60-nBn and C70-nBn(n = 1, 2), were successfully synthesized by DC arc burning method, extracted by CS2, and characterized by field desorption mass spectra. Among them C58B2 and C68B2 were extracted for the first time. The boron-doped fullerenes were found to be less stable than their pristine fullerene analogs. When the electric current becomes too high, no boron doped fullerene, but more higher fullerenes, were formed.

Synthesis and Characterization of Calcium Endohedral Fullerenes

Abstract The calcium endohedral fullerenes were synthesized by vaporizing the graphite anode filled with CaC2 grains with DC arc, extracted by CS2, and characterized by field desorption mass spectra. It is found that in the extract most fullerenes between C58 and C100 encapsulated one calcium atom and some trapped two calcium atoms inside. The results show that filling the graphite anode with CaC2 grains is more favorable to the formation of calcium endohedral fullerenes than filling with other materials.

High‐pressure synthesis of cyclic phenylacetylene oligomer

AbstractNew conjugated oligomers were prepared by reacting phenylacetylene under high pressure of 0.11 to 0.92 GPa at 100–200°C for 0–5 h. The number‐average molecular weight M̄n, the weight‐average molecular weight M̄w, and the oligomer yield increased with pressure, tem‐perature, and time. The average molecular weight of the oligomer showed the maximum value (M̄n: 830, M̄w: 2400) under 0.92 GPa, the maximum pressure, where phenylacetylene was oligomerized at a constant temperature. The structure of the oligomer was investigated from ESR, infrared, UV–VIS, field desorption mass (FDMS) spectra, and 13C NMR spec‐trum. Analysis of the FDMS spectrum revealed that the molecular weight of the oligomer was multiple of the monomer. 13C NMR spectrum of the oligomer showed the absence of sp‐carbon (C). We found that the oligomer had a cyclic structure. The cyclic oligomers of pentamer or more were new compounds. © 1995 John Wiley &amp; Sons, Inc.

Comparison of electrospray mass spectrometry with other soft ionization techniques for the characterisation of cationic π-hydrocarbon organometallic complexes

Electrospray (ES) mass spectrometry provides a convenient method for the characterisation of a wide range of π-hydrocarbon complex salts of the general types [FeCp(η-arene)]BF 4, [M(CO) 3(η-C 7H 7)BF 4 (MCr, Mo, W), [Fe(CO) 2L ( η 5-dienyl)]BF 4 L  CO or PPh 3; dienyl  C 6H 7, 2-MeOC 6H 6, or C 7H 9), [CpFe(CO) 3] PF 6 and [CpFe(CO) 2( η-C 2H 4)]BF 4. At low skimmer voltages (20 V), principal (molecular) ions are generally the only observed species. For the arene complexes, [FeCp( η-arene)]BF 4, high skimmer voltages (80–135 V) are required before fragmentation is observed. However, for the carbonyl containing cations, moderate skimmer voltages (40–55 V) also give rise to [MCO] +,[M2CO] + and [M3CO] + ions. Very similar behaviour is observed with phosphonium and imidazolium adducts of the type [Fe(CO) 3(η 4-diene. Nuc)] + ( diene  C 6 H 7 or C 7H 9; Nuc PPh 3 or Im) and [CpFe(CO) 2( η 1-C 2H 4·PPh 3)] +. comparison with fast atom bombardment (FAB) and field desorption (FD) mass spectra for the same complex salts indicates that fragmentation decreases along the series FAB > ES > FD, and that ES mass spectrometry is the most convenient and informative of the three soft ionization techniques.