Mass spectrometry of ammonium and iminium salts

Veith, H. J.

doi:10.1002/mas.1280020402

Cited by 46 publications

(29 citation statements)

References 85 publications

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“…+ C cluster ion, such species being frequently detected in FD-mass spectrometry. [50] Setting the rather narrow m/z 900-1300 range allowed sufficient resolution to be maintained at a comparatively fast scan rate. This turned out to be important to detect the intermediates during their short period of desorption.…”

Section: Wwwchemeurjorgmentioning

confidence: 99%

Living Radical Polymerization of Acrylates Mediated by 1,3‐Bis(2‐pyridylimino)isoindolatocobalt(II) Complexes: Monitoring the Chain Growth at the Metal

Langlotz

Lloret‐Fillol

Gross

et al. 2008

Chemistry A European J

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A new type of mediator for cobalt(II)-mediated radical polymerization is reported which is based on 1,3-bis(2-pyridylimino)isoindolate (bpi) as ancillary ligand. The modular synthesis of the bis(pyridylimino)isoindoles (bpiH) employed in this work is based on the condensation of 2-aminopyridines with phthalodinitriles. Reaction of the bpiH protio-ligands with a twofold excess of cobalt(II) acetate or cobalt(II) acetylacetonate in methanol gave [Co(bpi)(OAc)], which crystallize as coordination polymers, and a series of [Co(acac)(bpi)(MeOH)], which are mononuclear octahedral complexes. Upon heating the [Co(acac)(bpi)(MeOH)] compounds to 100 degrees C under high vacuum, the coordinated methanol was removed to give the five-coordinate complexes [Co(acac)(bpi)]. The polymerization of methyl acrylate at 60 degrees C was investigated by using one molar equivalent of the relatively short-lived radical source 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile) (V-70) as initiator (monomer/catalyst/V-70: 600:1:1). The low solubility of the acetato complexes inhibits their significant activity as mediators in this reaction, whereas the acetylacetonate complexes control the radical polymerization of methyl acrylate more effectively. The radical polymerizations of the hexacoordinate complexes did not show a linear increase in number-average molecular weight (M(n)) with conversion; however, the polydispersities were relatively low (PDI=1.12-1.40). By using the pentacoordinate complexes [Co(acac)(bpi)] as mediators, a linear increase in M(n) values with conversion, which were very close to the theoretical values for living systems, and very low polydispersities (PDI<1.13) were obtained. This was also achieved in the block copolymerization of methyl acrylate and n-butyl acrylate. The intermediates with the growing acrylate polymer radical ((.)PA) were identified by liquid injection field desorption/ionization mass spectrometry as following the general formula [Co(acac)(4-methoxy-bpi)-(MA)(n)-R] (MA: methyl acrylate; R: C(CH(3))(CH(2)C(CH(3))(2)OCH(3))CN), a notion also confirmed by NMR end-group analysis.

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Section: Wwwchemeurjorgmentioning

confidence: 99%

Living Radical Polymerization of Acrylates Mediated by 1,3‐Bis(2‐pyridylimino)isoindolatocobalt(II) Complexes: Monitoring the Chain Growth at the Metal

Langlotz

Lloret‐Fillol

Gross

et al. 2008

Chemistry A European J

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“…ϩ is a long known phenomenon in FD mass spectra of salts [47,48]; the value of n rises the larger the amount of sample placed onto the emitter surface and also depends on the actual salt. The assignment of the signals at higher m/z is further justified from the comparison of the experimental and calculated isotopic patterns, which reveal the presence of one boron atom at m/z 415.3 and two at m/z 666.4 due to the content of 10 B besides the most abundant boron isotope 11 B.…”

Section: Full Scan Lifdi Mass Spectra Of Ilmentioning

confidence: 99%

Liquid injection field desorption/ionization-mass spectrometry of ionic liquids

Gross

2007

J. Am. Soc. Mass Spectrom.

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Ten ionic liquids based on four types of organic cations, C ϩ (imidazolium, pyrrolidinium, pyridinium, and phosphonium), combined with various types of anions, AϪ, were analyzed by liquid injection field desorption/ionization-(LIFDI) mass spectrometry. For the purpose of LIFDI analysis the ionic liquids were dissolved in methanol, acetonitrile or tetrahydrofuran at concentrations of 0.01-0.1 l mL Ϫ1 . The measurements were performed on a double-focusing magnetic sector instrument. In all ionic liquid LIFDI spectra, the intact cation of the compound yielded the base peak accompanied by cluster ions of the general formula [C 2 A] ϩ and occasionally [C 3 A 2 ] ϩ . Tandem mass spectrometry and reconstructed ion chromatograms were employed to reveal the identity of the observed ions. Although limited to positive-ion mode, LIFDI also provided analytical information on the anions due to cluster ion formation. Depending on actual emitter condition and ionic liquid the limit of detection in survey scans was determined to 5-50 pg of ionic liquid. [1][2][3]. Consequently, there is a need for the development of methods for their analysis, be it for the sake of checking their purity, to verify their absence in products from processes where ILs are involved, or to monitor their distribution in the environment as a result of their long-term usage.Mass spectrometry (MS) offers various methods for the analysis of ionic analytes, with electrospray ionization (ESI) [4,5] and matrix-assisted laser desorption/ ionization (MALDI) [6,7] presently being the widest known techniques for that purpose. In addition, fast atom bombardment (FAB) [8,9] as well as field desorption (FD) [10 -12] Although being the longest established method for ionic analyte analysis, FD has been overlooked in this scenario of mass spectral techniques for IL analysis. Field desorption (FD) is known since the 1970s as a soft desorption/ionization method in mass spectrometry [10, 28 -30]. FD-MS has proven capabilities in analyzing nonionic low-to medium polarity compounds [12].FD employs strong electric fields in the order of 10 10 V m Ϫ1 (1 V Å Ϫ1 ) to effect the ionization of atoms and molecules [11,12,31]. The necessary field strength is normally achieved by setting whisker-bearing wiresso-called activated emitters [32][33][34]-to high electric potential of typically 10 -12 kV opposed to a counter electrode at ϳ2 mm distance. With the emitter at positive polarity, electron tunneling becomes possible from the analyte residing on the activated emitter's large surface into the emitter material. The analyte is thereby ionized very softly and the molecular ions generated are immediately extracted into the mass analyzer by action of the same electric field.Due to the advent of liquid injection field desorption/ionization (LIFDI) [35][36][37] the FD experiment can now be conducted easier, faster, and with more reproducibility than with the previous methodology of sample supply outside the ion source. If required, LIFDI offers fully inert sample transfer from se...

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“…Furthermore, it has been suggested that these reactions occur through a concerted mechanism or are mediated by the formation of radicals [6 -9]. The development of electrospray ionization allowed the formation of various classes of closed shell ions under very mild conditions and hence it has been unambiguously shown that at least in some cases homolytic C™C and C™H cleavages are involved in the gas phase decomposition of cationized organic compounds [10,11].One class of organic cations that are known to undergo homolytic cleavages is quaternary ammonium and pyridium cations [8,[12][13][14][15][16][17]. Fisher and Veith studied the gas phase fragmentation of ammonium and pyridinium ions, generated with field desorption and reported the formation of nitrogen based radical cations under collision induced dissociation (CID) [12,13].…”

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confidence: 99%

“…One class of organic cations that are known to undergo homolytic cleavages is quaternary ammonium and pyridium cations [8,[12][13][14][15][16][17]. Fisher and Veith studied the gas phase fragmentation of ammonium and pyridinium ions, generated with field desorption and reported the formation of nitrogen based radical cations under collision induced dissociation (CID) [12,13].…”

mentioning

confidence: 99%

“…Fisher and Veith studied the gas phase fragmentation of ammonium and pyridinium ions, generated with field desorption and reported the formation of nitrogen based radical cations under collision induced dissociation (CID) [12,13]. Harrison showed that the formation of radicals and cations from quaternary ammonium ions is dominated by the relative ionization potential of the appropriate radicals and neutrals, showing that the reaction products are the ones thermodynamically favored [14,15].…”

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confidence: 99%

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Homolytic cleavages in pyridinium ions, an excited state process

Denekamp

Tenetov

Horev

2003

J. Am. Soc. Mass Spectrom.

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The favored fragmentation pathway for protonated and alkylated pyridinium cations of the general formula p-XC 6 H 4 CH 2 CH 2 CH¢CH Py ϩ R (R¢H, Me; Py¢pyridine) is a C™C homolytic cleavage. The tendency to form radicals is higher for alkylated pyridinium cations than for the protonated ones that can also afford closed-shell products. Theoretical calculations show that the singlet-triplet gap for transient structures with an elongated benzylic C™C bond is very low and the formation of radicals may result from mixing of these states. In addition to the notable substituent effect on the fragmentation efficiency of the cations under study, calculated results show a clear substituent effect on the singlet-triplet transitions. We also observe that triphenylphosphonium cations behave notably different. Thus, the pyridinium system that contains a p-chloro benzyl moiety loses a benzyl radical readily while the analogous triphenylphosphonium cation is very stable under the same conditions. O rganic closed shell ions typically dissociate into closed shell ionic and neutral products. Nevertheless, there are exceptions to this rule that may result from lack of selectivity under extremely energetic conditions, unusual stability of some cation radicals or specific kinetic effects. It is reasonable that highly energetic conditions promote simple bond cleavage, either heterolytic or homolytic. Some radicals, however are generated under mild conditions and their formation can only be attributed to their relative stability.Different classes of organic closed-shell ions undergo C™C and C™N cleavages that are not necessarily charge driven [1][2][3][4][5]. Furthermore, it has been suggested that these reactions occur through a concerted mechanism or are mediated by the formation of radicals [6 -9]. The development of electrospray ionization allowed the formation of various classes of closed shell ions under very mild conditions and hence it has been unambiguously shown that at least in some cases homolytic C™C and C™H cleavages are involved in the gas phase decomposition of cationized organic compounds [10,11].One class of organic cations that are known to undergo homolytic cleavages is quaternary ammonium and pyridium cations [8,[12][13][14][15][16][17]. Fisher and Veith studied the gas phase fragmentation of ammonium and pyridinium ions, generated with field desorption and reported the formation of nitrogen based radical cations under collision induced dissociation (CID) [12,13]. Harrison showed that the formation of radicals and cations from quaternary ammonium ions is dominated by the relative ionization potential of the appropriate radicals and neutrals, showing that the reaction products are the ones thermodynamically favored [14,15]. Katritzky and coworkers studied homolytic cleavages in pyridium cations that were designed in order to show the substituent effect on the relative stability of radicals. They propose the term "merostabilization" to describe stabilization that results from the presence of both an electron-attracti...

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Mass spectrometry of ammonium and iminium salts

Cited by 46 publications

References 85 publications

Living Radical Polymerization of Acrylates Mediated by 1,3‐Bis(2‐pyridylimino)isoindolatocobalt(II) Complexes: Monitoring the Chain Growth at the Metal

Living Radical Polymerization of Acrylates Mediated by 1,3‐Bis(2‐pyridylimino)isoindolatocobalt(II) Complexes: Monitoring the Chain Growth at the Metal

Liquid injection field desorption/ionization-mass spectrometry of ionic liquids

Homolytic cleavages in pyridinium ions, an excited state process

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