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Study of the dissociation dynamics of transition metal complex ions
Transition metals play an important role in marine environments. They can be both essential and toxic for marine organisms. These metals are complexed by organic ligands, and their complexes are present at trace levels and in complicated mixtures making their analysis difficult. For this reason, sources and chemical compositions of these species remain unknown. This dissertation is centered on studying the dissociation dynamics of metal complexes in order to use mass spectrometry to get structural information for metal complexes at low concentration levels. This work describes the study of the collision-induced dissociation (CID) patterns and energetics exhibited by different metal complexes in a quadrupole ion trap mass spectrometer. ^ A variety of model ligands containing different donor atoms were synthesized and complexed with first-row transition metals. It was found that differences in the electronic structure of the metal ion, the coordination number of the complex, and the nature of the donor groups bound to the metal are reflected in the types of product ions observed in CID spectra. Upon dissociation, pentacoordinate complexes of Cu and Zn exhibited differences in the preference to remain coordinated to different donor group. For Cu, this preference reflected a balance between the inherent binding strength of the donor group and its flexibility. For Zn complexes, the inherent donor group binding strength and stability of the product ions were more important. ^ The metal electronic structure also impacted the types of dissociation products observed in penta-, and hexacoordinate complexes. Upon CID Cu tends to be reduced. For Zn H2 is the dominant dissociation pathway. Mn, Fe, Co, and Ni Complexes predominantly lose a single binding upon dissociation and sometimes Ni is reduced. ^ Relative dissociation energies were determined by a variable energy CID approach. Metal complexes having metal centers with smaller ionic radii had the lower dissociation energies, except for Cu(II) complexes because its easy reduction. ^ In summary, CID seems to have some promise for helping to distinguish among complexes with different coordinating functional groups, coordination numbers and/or metal centers and thus may some potential for providing coordination structure information for complexes present at trace concentration levels. ^
Chemistry, Analytical|Chemistry, Physical
Amanda L Chaparro,
"Study of the dissociation dynamics of transition metal complex ions"
(January 1, 2004).
Electronic Doctoral Dissertations for UMass Amherst.