Electronic Structure and Fragmentation Properties of [Fe4S4(SEt)4-X(SSEt)x]2-
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 FTICR (Fourier Transform Ion Cyclotron Resonance) 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. 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:
- Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 908501
- Report Number(s):
- PNNL-SA-53624; 3225; KC0301020
- Journal Information:
- International Journal of Mass Spectrometry, 263(2-3):260-266, Journal Name: International Journal of Mass Spectrometry, 263(2-3):260-266 Journal Issue: 2 Vol. 263; ISSN 0168-1176; ISSN IJMPDN
- Country of Publication:
- United States
- Language:
- English
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