Abstract
We investigated the photoionization and fragmentation of isolated metal protoporphyrin IX cations (MPPIX with M = Fe, Co, Zn) by means of VUV action spectroscopy in the energy range of 8.5-35 eV. Experiments were carried out in the gas phase by interfacing an electrospray ionization tandem mass spectrometer with a synchrotron beamline. The mass spectra and partial ion yields show that photoexcitation of the precursor ions predominantly leads to ? CH 2 COOH radical side-chain losses of the macrocycle with additional methyl radical ( ? CH 3 ) side-chain losses. Ionization, in contrast, leads to the formation of the intact ionized precursor and various doubly charged fragments which are mostly due to side-chain cleavages. Although statistical fragmentation dominates, we found evidence for non-statistical processes such as new fragments involving e.g. single and double H 2 O losses, indicating that different relaxation mechanisms are at play upon photoionization compared to photoexcitation. The measured ionization energies were 9.6 ± 0.2 eV, 9.4 ± 0.2 eV and 9.6 ± 0.2 eV for FePPIX + , CoPPIX + and ZnPPIX + , respectively.
Original language | English |
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Pages (from-to) | 12371-12379 |
Number of pages | 9 |
Journal | Chemistry |
Volume | 27 |
Issue number | 48 |
Early online date | 17-Jun-2021 |
DOIs | |
Publication status | Published - 25-Aug-2021 |
Keywords
- Electronic Structure
- Dissociation
- Mass Spectrometry
- Porphyrinoids
- VUV ActionSpectroscopy