title: Reduction of cationic free-base meso-tris-N-methylpyridinium-4-yl porphyrins in positive mode electrospray ionization mass spectrometry.
abstract: Reductions involving more than one electron with formation of the M+ and [M+2H]+ ions were observed for electrosprayed meso-tris(N-methylpyridinium-4-yl)porphyrin iodides, MI3. These reductions were studied by using different solvents and flow rates. Formation of the [M+2H]+ 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. Formation of the two reduced species, M+ and [M+2H]+ ions, may occur through the participation of counter ion/solvent clusters. Reduction of multiply charged, non-metallated species with formation of [M+nH]+ ions (n > 1) was not observed before in positive mode electrospray mass spectrometry.
authors.affiliation: Mass Spectrometry Laboratory, Department of Chemistry, University of Aveiro, Campus de Santiago, 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 Ferrer
authors.initials: AJ
authors.lastname: Correia
authors.forename: Vanda Vaz
authors.initials: VV
authors.lastname: Serra
authors.forename: João P C
authors.initials: JP
authors.lastname: Tomé
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