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Ionization and Photofragmentation of Isolated Metalloporphyrin Cations Investigated by VUV Action Spectroscopy **
Author(s) -
Schubert Kaja,
Schwob Lucas,
Dörner Simon,
Girod Marion,
MacAleese Luke,
Pieterse Cornelius L.,
Schlathölter Thomas,
Techert Simone,
Bari Sadia
Publication year - 2021
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.202101515
Subject(s) - photoionization , photoexcitation , chemistry , ionization , fragmentation (computing) , mass spectrometry , spectroscopy , electrospray ionization , photochemistry , ion , ionization energy , analytical chemistry (journal) , photodissociation , atomic physics , excited state , organic chemistry , physics , chromatography , quantum mechanics , computer science , operating system
We investigated the photoionization and fragmentation of isolated metal protoporphyrin IX cations (MPPIX + with M=Fe, Co, Zn) by means of vacuum‐ultraviolet (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 for example 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.