title: An electrospray ionization mass spectrometry study of azidoacetic acid/transition metal complexes.
abstract: BACKGROUND
  The complexation behavior of transition metals with organic azides by electrospray ionization (ESI) tandem mass spectrometry (MS/MS) is not completely understood. In this study, fragmentation patterns of complex ions having azidoacetic acid coordinated to Ni/Co/Fe were elucidated. The role of transition metals in the mediation of ligand rearrangements in gas phase is experimentally supported.
  
  
  METHODS
  The complexation of some transition metals, nickel, cobalt and iron, by azidoacetic acid was studied by means of ESI and MS/MS. Fragmentation patterns were discerned via consecutive MS/MS experiments on an ion trap mass spectrometer and confirmed by high-resolution (HR) Fourier transform ion cyclotron resonance MS. Density functional theory (DFT) calculations were used to characterize the major ions observed in MS.
  
  
  RESULTS
  Only singly positively charged complex ions were detected presenting various stoichiometries. MS/MS and theoretical calculations allowed us to confirm assignments and coordination sites. Structural evidence suggested that the azidoacetic acid can behave as monodentate and/or bidentate and coordination through the oxygen and nitrogen atoms are both possible. Experimental evidence strongly points to a role of Ni/Co/Fe, in oxidative state (I), in mediating C-C bond activation in the gas phase.
  
  
  CONCLUSIONS
  MS/MS and HRMS experiments were able to elucidate azidoacetic acid complexation with Ni/Co/Fe and several gas-phase processes involving metal reduction and rearrangements. The definition of the coordination pattern dictated by the competition between the nitrogen and the oxygen atoms is also dependent on the metal centre in a very dynamic process. Copyright © 2017 John Wiley & Sons, Ltd.
authors.affiliation: Departamento de Química e Bioquímica da Faculdade de Ciências da Universidade de Lisboa, Campo Grande, 1749-016, Lisboa, Portugal.
authors.forename: Vítor S
authors.initials: VS
authors.lastname: Pinto
authors.affiliation: Departamento de Química e Bioquímica da Faculdade de Ciências da Universidade de Lisboa, Campo Grande, 1749-016, Lisboa, Portugal.
authors.forename: Susana C R
authors.initials: SCR
authors.lastname: Marques
authors.affiliation: CQFB, Departamento de Química da Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa, Quinta da Torre, 2825-114, Monte da Caparica, Portugal.
authors.forename: Paula
authors.initials: P
authors.lastname: Rodrigues
authors.affiliation: CQFB, Departamento de Química da Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa, Quinta da Torre, 2825-114, Monte da Caparica, Portugal.
authors.forename: M Teresa
authors.initials: MT
authors.lastname: Barros
authors.affiliation: Laboratório de Instrumentação Engenharia Biomedica e Fsica da Radiação (LIBPhys-UNL), Departamento de Física, Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa, Monte da Caparica, 2892-516, Caparica, Portugal.
authors.forename: M Lourdes
authors.initials: ML
authors.lastname: Costa
authors.affiliation: Chemistry Department, University of Southampton, Highfield, Southampton, SO17 1BJ, UK.
authors.forename: G John
authors.initials: GJ
authors.lastname: Langley
authors.affiliation: CQB, Centro de Química e Bioquímica, Faculdade de Ciências da Universidade de Lisboa, Campo Grande, 1749-016, Lisboa, Portugal.
authors.forename: M Tereza
authors.initials: MT
authors.lastname: Fernandez
authors.affiliation: Departamento de Química e Bioquímica da Faculdade de Ciências da Universidade de Lisboa, Campo Grande, 1749-016, Lisboa, Portugal.|Grupo de Física Matemática da Universidade de Lisboa, Faculdade de Ciências da Universidade de Lisboa, Campo Grande, 1749-016, Lisboa, Portugal.
authors.forename: Benedito J C
authors.initials: BJC
authors.lastname: Cabral
authors.affiliation: CQB, Centro de Química e Bioquímica, Faculdade de Ciências da Universidade de Lisboa, Campo Grande, 1749-016, Lisboa, Portugal.
authors.forename: M Filomena
authors.initials: MF
authors.lastname: Duarte
authors.affiliation: ChELSI Institute, Department of Chemical and Biological Engineering, University of Sheffield, Mappin Street, Sheffield, S1 3JD, UK.
authors.forename: Narciso
authors.identifier: http://orcid.org/0000-0001-7565-4357
authors.initials: N
authors.lastname: Couto