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Electronic structure and fragmentation properties of [Fe4S4(SEt)4-x(SSEt)x]2-

Journal Article · · International Journal of Mass Spectrometry
 [1];  [1];  [1]
  1. Washington State Univ., Richland, WA (United States). Dept. of Physics; Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
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A limited exposure of (n-Bu4N)2[Fe4S4(SEt)4] solutions in acetonitrile to air was found to produce a new series of [4Fe–4S] cluster complexes, [Fe4S4(SEt)4-x(SSEt)x]2- (x = 1–4), with the original –SEt ligands substituted by –SSEt di-sulfide ligands, which were formed due to partial decomposition of the [4Fe–4S] core in parent [Fe4S4(SEt)4]2-. The products were first observed in the experiments with an ESI-ion Trap-TOF mass spectrometer and were further identified using high resolution Fourier transform ion cyclotron resonance (FTICR) mass spectrometer. Photoelectron spectra of the [Fe4S4(SEt)4-x(SSEt)x]2-dianions revealed that the –SSEt coordination induced little change in the electronic structure of the [4Fe–4S] cluster, but the electron binding energies of [Fe4S4(SEt)4-x(SSEt)x]2- increased from 0.52 to 0.73 eV with increase in x from 0 to 4, suggesting a greater electron withdrawing ability of –SSEt than –SEt. In high resolution MS/MS experiments on [Fe4S4(SEt)3(SSEt)]2-/1-, clusters with both charge states yielded fragment [Fe4S4(SEt)3]-, suggesting that –SSEt could be lost either as a negatively charged ion SSEt- from the doubly charged precursor, or as a radical SSEt from the singly charged species. Furthermore, the biological implication of the interaction between [Fe4S4(SEt)4]2- and O2 is discussed in comparison to the air exposure of [4Fe–4S] proteins to the air.

Research Organization:
Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Organization:
USDOE Office of Science (SC), Biological and Environmental Research (BER)
OSTI ID:
1152302
Journal Information:
International Journal of Mass Spectrometry, Journal Name: International Journal of Mass Spectrometry Journal Issue: 2-3 Vol. 263; ISSN 1387-3806
Publisher:
Elsevier
Country of Publication:
United States
Language:
English

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Related Subjects

Electrospray ionization source
FTMS
Fe–S protein
Photoelectron spectroctroscopy
Tandem mass spectrometry