title: Single electron redox via an ion-neutral complex in the fragmentation of protonated benzoylferrocenes.
abstract: BACKGROUND
  Ferrocene derivatives have become very popular molecules for biological applications. Although considerable experimental and theoretical calculation studies have demonstrated that ferrocene derivatives are easily oxidized during electrospray ionization (ESI), the details of the single electron redox reaction for protonated benzoylferrocenes in collision-induced dissociation (CID) mass spectrometry (MS) has not been obtained. Characterizing this mechanism is useful for further understanding the properties of ferrocene-containing biomaterials.
  
  
  METHODS
  All CID MS experiments were carried out using ESI ion trap mass spectrometry in positive ion mode. In addition, the accurate mass of fragments was measured on a ESI quadrupole time-of-flight (QTOF) mass spectrometer in positive ion mode. Theoretical calculations were carried out by the density functional theory (DFT) method with a hybrid basis set consisting of 6-31G (d) and ECP LanL2DZ in the Gaussian 03 program.
  
  
  RESULTS
  In the fragmentation of protonated benzoylferrocenes, the characterized ferrocinium cation was observed, which was proposed from the cleavage of the bond between the ipso-carbon atom and the carbonyl carbon followed by a single electron redox in [substituted benzoyl/ferrocene] complexes. Moreover, when the complex contained an oxidant (substituted benzoyl cation) with higher electron affinity, the single electron redox reaction was more efficient. A correlation was established between the intensities of the two competitive product ions and the electron affinities of substituted benzoyl cations.
  
  
  CONCLUSIONS
  The single electron redox reaction by the [substituted benzoyl/ferrocene] complexes was proposed by CID MS and theoretical calculations, which provided potential evidence to further understand the reversible reduction characteristics of ferrocene-containing biomaterials.
authors.affiliation: Research Center of Analysis and Measurement, Zhejiang University of Technology, 18 Chaowang Rd, Hangzhou, Zhejiang, 310014, PR China. xiaojicao@zjut.edu.cn
authors.forename: Xiaoji
authors.initials: X
authors.lastname: Cao
authors.forename: Nan
authors.initials: N
authors.lastname: Jiang
authors.forename: Xuemin
authors.initials: X
authors.lastname: Ye
authors.forename: Lebin
authors.initials: L
authors.lastname: Zheng
authors.forename: Feifei
authors.initials: F
authors.lastname: Zhang
authors.forename: Lingxiao
authors.initials: L
authors.lastname: Shen
authors.forename: Jiaoyu
authors.initials: J
authors.lastname: Chen
authors.forename: Weimin
authors.initials: W
authors.lastname: Mo
mesh_terms: D004583:Electrons; D005296:Ferrous Compounds / Q000737:chemistry*; D007477:Ions; D008958:Models, Molecular; D010084:Oxidation-Reduction; D011522:Protons; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D013816:Thermodynamics
chemical_list: D005296:Ferrous Compounds; D007477:Ions; D011522:Protons