title: Reduction and adduct formation from electrosprayed solutions of porphyrin salts.
abstract: The solutions of four meso-tetrakis(N-alkylpyridinium-4-yl)porphyrin salts and of the p-toluenesulfonate salt of meso-tetrakis(4-trimethylammoniumphenyl)porphyrin, in methanol, were studied by electrospray mass spectrometry, in order to investigate the influence of the type of counter ion, the length of the substituent N-alkyl groups of the four (N-alkylpyridinium-4-yl)porphyrins and the presence of an aromatic (alkylpyridinium) or aliphatic (trimethylammonium) nitrogen, in ion formation. In our experimental conditions, adducts with the counter ions were formed only for the meso-tetrakis(4-trimethylammoniumphenyl)porphyrin and were not observed for the other porphyrins, even when the counter ion was the same. In contrast, formation of reduced species, such as the [M(4+) + e(-)]3+, [M(4+) + 2e(-)]2+, [M(4+) + 4e(-) + 2H(+)]2+, and [M(4+) + 5e(-) + 2H(+)]+ ions was observed only for the (N-alkylpyridinium-4-yl)porphyrins and the appearance of these species is apparently solvent related and may occur via counter ion/solvent adducts.
authors.affiliation: Mass Spectrometry Laboratory, Department of Chemistry, University of Aveiro, Campus de Santiago, 3810-193 Aveiro, Portugal.
authors.forename: Catarina I V
authors.initials: CI
authors.lastname: Ramos
authors.forename: M Graça
authors.initials: MG
authors.lastname: Santana-Marques
authors.forename: A J
authors.initials: AJ
authors.lastname: Ferrer Correia
authors.forename: João P C
authors.initials: JP
authors.lastname: Tomé
authors.forename: Cristina M
authors.initials: CM
authors.lastname: Alonso
authors.forename: Augusto C
authors.initials: AC
authors.lastname: Tomé
authors.forename: M Graça P M S
authors.initials: MG
authors.lastname: Neves
authors.forename: J A S
authors.initials: JA
authors.lastname: Cavaleiro
mesh_terms: D002412:Cations / Q000737:chemistry; D000432:Methanol / Q000737:chemistry; D011166:Porphyrins / Q000737:chemistry*; D011726:Pyridinium Compounds / Q000737:chemistry*; D000644:Quaternary Ammonium Compounds / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization
chemical_list: D002412:Cations; D011166:Porphyrins; D011726:Pyridinium Compounds; D000644:Quaternary Ammonium Compounds; C530372:meso-tetrakis(4-trimethylammoniumphenyl)porphyrin; D000432:Methanol