Studying Fragmentation Of Aromatic Ligand And Transition-Metal Compounds Using Mass Spectrometry

The mass spectrometry has been concerned extensively with the rapid development of new mass spectrometry technologies and has developed in many fields greatly. In this thesis, the fragmentation mechanisms and the active cleavage sites of ferrocene compounds, nickel phenanthroline complexes and diene ligands were studied using tandem mass spectrometry with atmospheric pressure ion source. On the other hand, the fragmentation pathways of diene ligands were also investigated by electron impact (EI) ion source. Furthermore, the fragmentation mechanisms of diene ligands by these two kinds of ion sources were compared in detail.First, the fragmentation mechanisms of ferrocene compounds were discussed using collision induced dissociation (CID) with electrospray ionization (ESI). As the results shown, the cleavage sites were closely related to electronegativity and steric effect of substituents. For formamide ferrocenes with electron-withdrawing group, the protonated-ability of N atom is stronger than that of O atom, which will promote the breakage of C-N bond of formamide group. However, in the CID process, the neutral loss of cyclopentadienyl is dominated for methylenimine ferrocenes due to the protoned site on the ferrocene nucleus. Different from the former compounds, the fragment ions of formoxyl ferrocene were formed by the cleverage of formoxyl.Secondly, fragmentation mechanisms of the nickel phenanthroline complexes were also investigated by ESI. The leading fragment ions were produced by neutral loss of ligand from complexes ions. Furthermore, for the complexes containing ligand with active H, the interligand proton transfer reaction occurred. As a result, the complemental monocation pair generated. Amazingly, these complexes were liable to be solvated by various solvents (CH₃CN, CH₃OH and H₂O), which had great relationship with the valence and coordination number of the complexes. When the complexes were divalent with two ligands or univalent with one ligand, the complexes were apt to coordinate with the solvent moleculars (such as CH₃CN, CH3OH and H₂O).Finally, for the diene ligands, the effect of substituents on the fragmentation mechanisms was evaluated using EI source and APCI source, respectively. It was easily to lose Br and Cl radical. Moreover, the skeletal rearrangement reaction, which a five-membered ring formed, was favored in the fragmental process.