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Title: Electronic structure and fragmentation properties of [Fe 4S 4(SEt) 4-x(SSEt) x] 2-

Abstract

A limited exposure of (n-Bu 4N) 2[Fe 4S 4(SEt) 4] solutions in acetonitrile to air was found to produce a new series of [4Fe–4S] cluster complexes, [Fe 4S 4(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 [Fe 4S 4(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 [Fe 4S 4(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 [Fe 4S 4(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 [Fe 4S 4(SEt) 3(SSEt)] 2-/1-, clusters with both charge states yielded fragment [Fe 4S 4(SEt) 3] -, suggesting that –SSEt could be lost either as a negatively charged ion SSEt- from the doubly charged precursor, or as a radical SSEtmore » from the singly charged species. Furthermore, the biological implication of the interaction between [Fe 4S 4(SEt) 4] 2- and O 2 is discussed in comparison to the air exposure of [4Fe–4S] proteins to the air.« less

Authors:
 [1];  [1];  [1]
  1. Washington State Univ., Richland, WA (United States). Dept. of Physics; Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Publication Date:
Research Org.:
Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org.:
USDOE Office of Science (SC), Biological and Environmental Research (BER)
OSTI Identifier:
1152302
Resource Type:
Journal Article
Resource Relation:
Journal Name: International Journal of Mass Spectrometry; Journal Volume: 263; Journal Issue: 2-3
Country of Publication:
United States
Language:
English
Subject:
FTMS; Electrospray ionization source; Tandem mass spectrometry; Photoelectron spectroctroscopy; Fe–S protein

Citation Formats

Fu, You-Jun, Laskin, Julia, and Wang, Lai-Sheng. Electronic structure and fragmentation properties of [Fe4S4(SEt)4-x(SSEt)x]2-. United States: N. p., 2007. Web. doi:10.1016/j.ijms.2007.03.001.
Fu, You-Jun, Laskin, Julia, & Wang, Lai-Sheng. Electronic structure and fragmentation properties of [Fe4S4(SEt)4-x(SSEt)x]2-. United States. doi:10.1016/j.ijms.2007.03.001.
Fu, You-Jun, Laskin, Julia, and Wang, Lai-Sheng. Fri . "Electronic structure and fragmentation properties of [Fe4S4(SEt)4-x(SSEt)x]2-". United States. doi:10.1016/j.ijms.2007.03.001.
@article{osti_1152302,
title = {Electronic structure and fragmentation properties of [Fe4S4(SEt)4-x(SSEt)x]2-},
author = {Fu, You-Jun and Laskin, Julia and Wang, Lai-Sheng},
abstractNote = {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.},
doi = {10.1016/j.ijms.2007.03.001},
journal = {International Journal of Mass Spectrometry},
number = 2-3,
volume = 263,
place = {United States},
year = {Fri Jun 01 00:00:00 EDT 2007},
month = {Fri Jun 01 00:00:00 EDT 2007}
}
  • 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,more » 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.« less
  • The first microporous solids incorporating two octahedrally coordinated transition elements, the phosphates (TMA)[sub 2](NH[sub 4])[sub 2][Fe[sub 2]Mo[sub 12]O[sub 30](H[sub 2]PO[sub 4])[sub 6](HOP[sub 4])[sub 2]][center dot]11H[sub 2]O (1) and (TMA)[sub 2]Na[sub 4][Fe[sub 3]Mo[sub 12]O[sub 30](H[sub x]PO[sub 4])[sub 8]][center dot]16H[sub 2]O (2) (TMA = (CH[sub 3])[sub 4]N[sup +]), have been hydrothermally synthesized and characterized by single-crystal X-ray diffraction and water absorption isotherms. Phosphate 1 is prepared in 94% yield from Na[sub 2]MoO[sub 4], Mo, FeCl[sub 3], (NH[sub 4])[sub 2]HPO[sub 4], (TMA)OH, H[sub 3]PO[sub 4], and H[sub 2]O in a mole ratio of 5:1:1:2:7:16:150 at 200[degrees]C for 64 h, while 2 is synthesizedmore » in 62% yield by the reaction of Na[sub 2]MoO[sub 4], Mo, FeCl[sub 3], (TMA)OH, H[sub 3]PO[sub 4] and H[sub 2]O in a mole ratio of 5:1:1:8:18:250 at 200[degrees]C for 3 days. Orange crystals of 1 are rhombohedral. Both structures are based on Fe[Mo[sub 6]O[sub 15](H[sub x]PO[sub 4])[sub 2]] units which are connected via their phosphate groups to additional Fe[sup 3+] ions to give three-dimensional frameworks. Both compounds display structures that can be rationalized on the basis of regions of hydrophobic and hydrophilic interactions. The interconnected voids and channels in the ferric molybdenum phosphate frameworks are filled with a mixture of charged-compensating cations and water of solvation. Reversible water absorption isotherms indicate that both compounds are microporous with internal void volumes of about 15 and 25 vol % for 1 and 2, respectively. 23 refs., 10 figs., 3 tabs.« less
  • The [M{sub x}{sup II}M{sub 2.5-x}{sup III}(H{sub 2}O){sub 2}(HP{sup III}O{sub 3}){sub y}(P{sup V}O{sub 4}){sub 2-y}F; M=Fe (1), x=2.08, y=1.58; M=Co (2), x=2.5, y=2; Ni (3), x=2.5, y=2] compounds have been synthesized using mild hydrothermal conditions at 170 deg. C during five days. Single-crystals of (1) and (2), and polycrystalline sample of (3) were obtained. These isostructural compounds crystallize in the orthorhombic system, space group Aba2, with a=9.9598(2), b=18.8149(4) and c=8.5751(2) A for (1), a=9.9142(7), b=18.570(1) and c=8.4920(5) A for (2) and a=9.8038(2), b=18.2453(2) and c=8.4106(1) A for (3), with Z=8 in the three phases. An X-ray diffraction study reveals that themore » crystal structure is composed of a three-dimensional skeleton formed by [MO{sub 5}F] and [MO{sub 4}F{sub 2}] (M=Fe, Co and Ni) octahedra and [HPO{sub 3}] tetrahedra, partially substituted by [PO{sub 4}] tetrahedra in phase (1). The IR spectra show the vibrational modes of the water molecules and those of the (HPO{sub 3}){sup 2-} tetrahedral oxoanions. The thermal study indicates that the limit of thermal stability of these phases is 195 deg. C for (1) and 315 deg. C for (2) and (3). The electronic absorption spectroscopy shows the characteristic bands of the Fe(II), Co(II) and Ni(II) high-spin cations in slightly distorted octahedral geometry. Magnetic measurements indicate the existence of global antiferromagnetic interactions between the metallic centers with a ferromagnetic transition in the three compounds at 28, 14 and 21 K for (1), (2) and (3), respectively. Compound (1) exhibits a hysteresis loop with remnant magnetization and coercive field values of 0.72 emu/mol and 880 Oe, respectively. - Abstract: Polyhedral view of the crystal structure of the [M{sub x}{sup II}M{sub 2.5-x}{sup III}(H{sub 2}O){sub 2}(HP{sup III}O{sub 3}){sub y}(P{sup IV}O{sub 4}){sub 2-y}F; M=Fe, x=2.08, y=1.58; M=Co, Ni, x=2.5, y=2] compounds showing the sheets along the [001] direction.« less
  • Second order configuration interaction wave functions based on molecular orbitals determined from a state-averaged multiconfigurational self-consistent field procedure are used to investigate the intermediate complex driven model for the spin-forbidden reaction CH{sub 3}(X{sup 2}A{sub 2}{sup {double_prime}})+N({sup 4}S){r_arrow}HCN(X{sup 1}{Sigma}{sup +})+H{sub 2}(X{sup 1}{Sigma}{sup +}). The minimum energy crossing point (MECP), the minimum energy point on the surface of intersection connecting the reactant channel, {sup 3}A{sup {prime}{prime}} potential energy surface, and product channel {sup 1}A{sup {prime}} potential energy surface, is determined directly, i.e., without {ital a priori} characterization of the individual potential energy surfaces. The MECP is found to be 8.2 kcal/mol belowmore » of the reactants. The structure at the MECP clearly evinces the incipient formation of a H{sub 2} bond. Barrierless paths from the reactants to the intermediate complex-methylnitrene, from the intermediate complex to the MECP, and from the MECP to the products are established. The absence of a barrier on these paths supports the intermediate complex mechanism. Spin{endash}orbit interactions are determined to be {approximately}30cm{sup {minus}1} for points on the surface of intersection in the vicinity of the MECP. Spin{endash}orbit interactions and the local potential surface topology at the MECP are used to probe the efficiency of the intersystem crossing using the Landau{endash}Zener model. A reduced dimensionality model is proposed. {copyright} {ital 1997 American Institute of Physics.}« less
  • Solids of the composition La{sub 2{minus}x}Sr{sub x}Li{sub 1/2}Co{sub 1/2}O{sub 4} (x = 0, x {approx_equal} 0.2) crystallize in a superstructure of the K{sub 2}NiF{sub 4} lattice with a doubled unit cell in the (001) plane (space group Ammm; a = b = {radical}2a{sub 0}), caused by cation ordering between lithium and cobalt on the octahedral sites. The electronic structure of the Co{sup III}O{sub 6} and Co{sup IV}O{sub 6} polyhedra, which lie isolated in the lattice, were studied by various spectroscopic techniques (XANES, EPR, optical). The groundstates are low-spin in both cases (t{sub 2g}{sup 6} and t{sub 2g}{sup 5}, respectively), themore » ligand field parameters of Co{sup III} being close to those characterizing the high-spin/low-spin crossover.« less