title: Characterization of dinitroporphyrin zinc complexes by electrospray ionization tandem mass spectrometry. Unusual fragmentations of beta-(1,3-dinitroalkyl) porphyrins.
abstract: The zinc complexes of diaryl bis(p-nitrophenyl)porphyrins and beta-(1,3-dinitroalkyl)tetraphenylporphyrins were studied by electrospray ionization (ESI) tandem mass spectrometry (MS/MS). All porphyrins showed the protonated molecule under ESI conditions. The protonated molecules were induced to fragment and the corresponding ESI tandem mass spectra were analysed. Porphyrins with two p-nitrophenyl groups showed, as expected, characteristic fragmentations including either loss of one nitro group, as the major fragment of the tandem mass spectra, and loss of both nitro groups. In contrast, MS/MS of the beta-(1,3-dinitroalkyl)porphyrins provided interesting and unexpected results such as the absence (or in insignificant abundance) of the ions formed by loss of one nitro group. However, these porphyrins show an abundant fragment due to combined loss of the two nitro groups. Also, the typical beta-cleavage of the alkyl chain is not observed per se, only when combined with loss of HNO2 or *NO2. Instead, alpha-cleavage, with loss of the beta-pyrrolic substituent, is the most favourable process.
authors.affiliation: Department of Chemistry, University of Aveiro, 3810-193 Aveiro, Portugal.
authors.forename: E M P
authors.initials: EM
authors.lastname: Silva
authors.forename: M R M
authors.initials: MR
authors.lastname: Domingues
authors.forename: C
authors.initials: C
authors.lastname: Barros
authors.forename: M A F
authors.initials: MA
authors.lastname: Faustino
authors.forename: J P C
authors.initials: JP
authors.lastname: Tomé
authors.forename: M G P M S
authors.initials: MG
authors.lastname: Neves
authors.forename: A C
authors.initials: AC
authors.lastname: Tomé
authors.forename: M G
authors.initials: MG
authors.lastname: Santana-Marques
authors.forename: J A S
authors.initials: JA
authors.lastname: Cavaleiro
authors.forename: A J
authors.initials: AJ
authors.lastname: Ferrer-Correia
mesh_terms: D009574:Nitro Compounds / Q000737:chemistry*; D009942:Organometallic Compounds / Q000737:chemistry*; D011166:Porphyrins / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D015032:Zinc / Q000737:chemistry*
chemical_list: D009574:Nitro Compounds; D009942:Organometallic Compounds; D011166:Porphyrins; D015032:Zinc