Secondary ion mass spectra of diquaternary ammonium salts

Ryan, Timothy M.; Day, Richard E.; Cooks, R. Graham

doi:10.1021/ac50063a014

Cited by 72 publications

(39 citation statements)

References 15 publications

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“…Detection of similar hypervalent radicals formed by one electron reduction of quaternary ammonium (and phosphonium) salts in the gas phase, by using several mass spectrometric techniques, has been known°since°1980° [25]°and°is°extensively°documented Observation of the [Mϩ2H] ϩ ions could be attributable either to chlorin contamination of the porphyrin samples or to an unlikely solution reduction (instantaneous upon dissolution, or overnight). These hypotheses were ruled out through acquisition of the UVvisible spectra of methanol solutions of the porphyrins, freshly prepared, and after 24 h. No significant alter- Reduction reactions in the metal capillary sprayers of mass spectrometers operating in the negative mode are an important step in the overall ionization process, being responsible for charge balance, but in the positive mode°this°balance°is°achieved°through°oxidation° [1,°2].…”

Section: Resultsmentioning

confidence: 99%

Reduction of cationic free-base meso-tris-N-methylpyridinium-4-yl porphyrins in positive mode electrospray ionization mass spectrometry

Ramos

Marques

Correia

et al. 2007

J. Am. Soc. Mass Spectrom.

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Reductions involving more than one electron with formation of the M ϩ and [Mϩ2H] ϩ ions were observed for electrosprayed meso-tris (N-methylpyridinium-4-yl)porphyrin iodides, MI 3 . These reductions were studied by using different solvents and flow rates. Formation of the [Mϩ2H] ϩ ions occurred only for protic solvents and to a larger extent at lower flow rates. The type of the fourth substituent does not seem to affect the reduction processes. , it is generally accepted that redox reactions do occur in the capillary sprayers and that they are responsible for charge balance [1,2]. Redox processes in electrospray mass spectrometry were comprehensively investigated by and, more recently, electrochemical aspects and applications of electrospray ionization were the focus of reviews [9,10].Ions formed by one electron reduction from nonmetallated dicationic species in solution were previously observed in positive-mode electrospray mass spectrometry for ionic compounds such as diquaternary pyridinium salts [11-13] and free-base N-alkylpyridiniumyl porphyrin salts [14]. One-and two-electron reductions of the cations of metallated N-alkylpyridiniumyl porphyrin salts were also reported, when electrospray was used in the positive mode [15][16][17].When acquiring the electrospray mass spectra of 5,10,15-tris(N-methyl-pyridinium-4-yl)-20-phenylporphyrin iodide, MI 3 , we observed, besides the expected M 3ϩ ion, ions such as M 2ϩ , M ϩ , and [Mϩ2H] ϩ , which may be the result of reductive processes. Reductions involving more than one electron were never reported before for electrosprayed free-base cationic porphyrins and, although formation of [MϩnH] ϩ ions (n Ͼ 1) in desorption ionization (fast atom or ion bombardment) [18 -20] and matrix assisted laser desorption (MALDI) [21] has been described, it was never reported as occurring in electrospray mass spectrometry (ESI-MS) until now. These facts prompted us to use ESI-MS to investigate a group of meso-tris(N-methylpyridinium-4-yl)porphyrin iodides, MI 3 , with a different fourth meso substituent (see Scheme 1) to gather more information on the species formed with respect to their formation reactions and to their relation with the ionization processes occurring in the electrospray interface. ExperimentalThe key neutral porphyrin derivatives were obtained from crossed-Rothemund reactions using the appropriate benzaldehydes and pyrrole in refluxing acetic acid and nitrobenzene [22][23][24]. The alkylation with methyl

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Section: Resultsmentioning

confidence: 99%

Reduction of cationic free-base meso-tris-N-methylpyridinium-4-yl porphyrins in positive mode electrospray ionization mass spectrometry

Ramos

Marques

Correia

et al. 2007

J. Am. Soc. Mass Spectrom.

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“…Quelques resultats de la litterature concernent I'identification de sels organiques comportant un cation doublernent charge (composes du type CX, ) par spectrometrie de rnasse a I'aide de methodes d'ionisation par desorption et plus particulierernent a I'aide de la methode d'ionisation FAB [6,7,8,9] Les composes du type C + -t 2X-etudies dans des travaux anterieurs de la litterature [6.7,8,9] presentent dans leurs spectres en mode positif trois ions portant une seule charge formes a partir du cation doublement charge C -k + par les trois processus suivants : de I'anion.…”

Section: Resultats Et Discussionunclassified

“…Ces trois processus ont notarnrnent ete observes [6,7,8,9] Spectre de masse FAB du compose 1p (Matrice NBA).…”

Section: Resultats Et Discussionunclassified

Spectres de Masse FAB en Mode Positif de Cations Hétérocycliques Doublement Charges Apparentes au Dibenzo[a,e]Cyclooctane

Aubagnac

Claramunt

Lavandera

et al. 1991

Bulletin des Soc Chimique

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SUMMARYFAB mass spectra in positive mode of doubly charged heterocyclic cations allow identification of such structures. Furthermore, two characteristics of these spectra (low abundance of the doubly charged cations and the reduction phenomenon) are in agreement with previous results. INTRODUCTIONLa rnethode d'ionisation FAB est particulierement adaptee a I'etude de composes polaires par spectrometrie de mass8 [1,2]. Ainsi, elk permet la caracterisation aisee de sels organiques [3,4]. Un compose organique du type C +A-(C+ : cation -A-: anion presente avec des abondances notable le cation C+ dans le spectre FAB en mode positif et I'anion A-dans le spectre FAB en mode negatif. Par exemple,

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“…They reported that doubly charged ions were observed only for compounds with Coulombic repulsion energies between 1.3 and 1.5 eV. Ryan et al 29 reported that the intercharge distances were used to calculate Coulombic repulsive energies ( T ) from T (eV) = 14.6/r (A), where r is the distance between charges. Using this method, the calculated Coulombic repulsion energies for the doubly charged cations discussed here are 1.7 eV for propidium iodide, 1.6 eV for true blue and 0.6 eV for RH-414.…”

Section: Heller Etmentioning

confidence: 99%

Investigation of cationic organic dyes used as molecular probes by liquid secondary ion mass spectrometry

Carlson

Busch

1994

Org. Mass Spectrom.

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The positive-ion mass spectra of twelve organic dyes used as molecular probes were measured using liquid secondary ion mass spectrometry (LSIMS). Nine of the twelve dyes were singly charged cations and the other three were doubly charged cations. The mass spectra of each of the dyes in m-nitrobenzyl alcohol contain abundant signals for the intact cation, C+ (singly charged cation dyes), or for singly-charged forms of the doubly charged cation formed by proton loss, [C2+ -H + ] + , or halogen counter ion attachment, [C2+ + X-1'. Fragmentation is usually minimal under the conditions used. However, the cations of five of the singly charged compounds appear to undergo charge-remote fragmentation. Collision-induced dissociation experiments on a hybrid mass spectrometer of EBqQ geometry at collision energies up to 300 eV failed to access this fragmentation pathway. In contrast to the LSIMS of many other doubly charged organic compounds, two of the dicationic dyes produced a doubly charged ion of reasonable abundance (220%) in the mass spectrum. When glycerol was used as a matrix solvent, the addition of the matrix modifier trifluoroacetic acid increased the abundance of C2+.

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Secondary ion mass spectra of diquaternary ammonium salts

Cited by 72 publications

References 15 publications

Reduction of cationic free-base meso-tris-N-methylpyridinium-4-yl porphyrins in positive mode electrospray ionization mass spectrometry

Reduction of cationic free-base meso-tris-N-methylpyridinium-4-yl porphyrins in positive mode electrospray ionization mass spectrometry

Spectres de Masse FAB en Mode Positif de Cations Hétérocycliques Doublement Charges Apparentes au Dibenzo[a,e]Cyclooctane

Investigation of cationic organic dyes used as molecular probes by liquid secondary ion mass spectrometry

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