Terahertz, infrared and Raman vibrational assignments of [FeFe]-hydrogenase model compounds

Stromberg, Christopher J.; Kohnhorst, Casey; Meter, Glenn A. Van; Rakowski, Elizabeth A.; Caplins, Benjamin C.; Gutowski, Tiffany A.; Mehalko, Jennifer; Heilweil, Edwin J.

doi:10.1016/j.vibspec.2011.02.012

Cited by 11 publications

(9 citation statements)

References 58 publications

(102 reference statements)

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“…RR spectra of H 2 ‐reduced MBH, measured with a 458 nm excitation at 79 K, display distinct vibrational bands between 400 and 650 cm −1 (Figure 1 A, black line), whereas comparable signals are not observed in the spectrum of the oxidized, as‐isolated (untreated) enzyme. The monitored bands appear in the spectral range characteristic of FeCO/CN stretching and bending modes,10 as also reported for hydrogenase model compounds 11–13. Contributions from iron–sulfur cluster modes can be excluded as they are lower in frequency and, owing to the resonance enhancement through S→Fe charge‐transfer transitions, primarily detectable in the oxidized states 14.…”

Section: Experimental Frequencies and Isotopic Shifts Of The Active Site Modes Of H2‐reduced Mbh And Calculated Values For Ni‐l Nia‐c Andsupporting

confidence: 52%

“…The monitored bands appear in the spectral range characteristic of FeÀCO/CN stretching and bending modes, [10] as also reported for hydrogenase model compounds. [11][12][13] Contributions from iron-sulfur cluster modes can be excluded as they are lower in frequency and, owing to the resonance enhancement through S!Fe chargetransfer transitions, primarily detectable in the oxidized states. [14] These conclusions are supported by Raman spectra calculated for the active site of the MBH by means of a hybrid quantum mechanical/molecular mechanical (QM/MM) model that was recently constructed on the basis of a computationally refined crystal structure of reduced MBH (for computational details, see the Supporting Information SI5).…”

Section: In Memory Of Gernot Rengermentioning

confidence: 99%

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Resonance Raman Spectroscopy as a Tool to Monitor the Active Site of Hydrogenases

et al. 2013

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Insights in active sites: Hydrogen‐conversion by hydrogenase is mediated by a sophisticated, metal‐containing catalytic center. Resonance Raman spectroscopy is used for the first time in the characterization of the active site of these biocatalysts. An integrated spectroscopic and computational approach gives insights into structural and photochemical properties of the active site of an oxygen‐tolerant [NiFe] hydrogenase.

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Section: Experimental Frequencies and Isotopic Shifts Of The Active Site Modes Of H2‐reduced Mbh And Calculated Values For Ni‐l Nia‐c Andsupporting

confidence: 52%

Section: In Memory Of Gernot Rengermentioning

confidence: 99%

Resonance Raman Spectroscopy as a Tool to Monitor the Active Site of Hydrogenases

et al. 2013

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“…74 In combination with quantum chemical calculations, Raman spectroscopy has been used recently to assign vibrational frequencies of, e.g., bridging and terminal Fe-H bonds. [75][76][77][78] Synchrotron-based X-ray absorption and emission spectroscopy (XAS, XES) and resonant inelastic X-ray scattering (RIXS) permit the study of all states of [FeFe] compounds in solid material and in solution. [79][80][81][82][83] By the combination of highresolution XAS and narrow-band detection XES in a single experiment (XAES), 79,80,[84][85][86][87][88][89][90][91][92] specific structural features (interatomic distances, site geometry, ligation patterns) and electronic properties (metal oxidation and spin states; molecular orbital energies, occupancies, and interactions) are derived, in an even spin-and site-selective fashion.…”

Section: Introductionmentioning

confidence: 99%

Bridging-hydride influence on the electronic structure of an [FeFe] hydrogenase active-site model complex revealed by XAES-DFT

et al. 2013

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Two crystallized [FeFe] hydrogenase model complexes, 1 = (μ-pdt)[Fe(CO)(2)(PMe(3))](2) (pdt = SC1H2C2H2C3H2S), and their bridging-hydride (Hy) derivative, [1Hy](+) = [(μ-H)(μ-pdt)[Fe(CO)(2) (PMe(3))](2)](+) (BF(4)(−)), were studied by Fe K-edge X-ray absorption and emission spectroscopy, supported by density functional theory. Structural changes in [1Hy](+) compared to 1 involved small bond elongations (<0.03 Å) and more octahedral Fe geometries; the Fe–H bond at Fe1 (closer to pdt-C2) was ~0.03 Å longer than that at Fe2. Analyses of (1) pre-edge absorption spectra (core-to-valence transitions), (2) Kβ(1,3), Kβ', and Kβ(2,5) emission spectra (valence-to-core transitions), and (3) resonant inelastic X-ray scattering data (valence-to-valence transitions) for resonant and non-resonant excitation and respective spectral simulations indicated the following: (1) the mean Fe oxidation state was similar in both complexes, due to electron density transfer from the ligands to Hy in [1Hy](+). Fe 1s→3d transitions remained at similar energies whereas delocalization of carbonyl AOs onto Fe and significant Hy-contributions to MOs caused an ~0.7 eV up-shift of Fe1s→(CO)s,p transitions in [1Hy](+). Fed-levels were delocalized over Fe1 and Fe2 and degeneracies biased to O(h)–Fe1 and C(4v)–Fe2 states for 1, but to O(h)–Fe1,2 states for [1Hy](+). (2) Electron-pairing of formal Fe(d(7)) ions in low-spin states in both complexes and a higher effective spin count for [1Hy](+) were suggested by comparison with iron reference compounds. Electronic decays from Fe d and ligand s,p MOs and spectral contributions from Hys,p→1s transitions even revealed limited site-selectivity for detection of Fe1 or Fe2 in [1Hy](+). The HOMO/LUMO energy gap for 1 was estimated as 3.0 ± 0.5 eV. (3) For [1Hy](+) compared to 1, increased Fed (x(2) − y(2)) − (z(2)) energy differences (~0.5 eV to ~0.9 eV) and Fed→d transition energies (~2.9 eV to ~3.7 eV) were assigned. These results reveal the specific impact of Hy-binding on the electronic structure of diiron compounds and provide guidelines for a directed search of hydride species in hydrogenases.

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“…Notably, the KBr pellet data of 2 were characterized by a broadened and almost featureless peak pattern (see the Supporting Information), which sometimes occurs for this class of compounds in the solid state. 20 Well-resolved spectra could be obtained for both clusters only in the liquid phase. The infrared spectrum of the iron–sulfur complex 1 in CH 2 Cl 2 solution displays a set of three main carbonyl band maxima and two additional shoulders in the = 1900–2100 cm –1 region for ν(CO) stretching vibration (Figure 1 ).…”

Section: Resultsmentioning

confidence: 99%

“…The FTIR spectra of the triiron clusters were measured both in solution and in the solid phase. Notably, the KBr pellet data of 2 were characterized by a broadened and almost featureless peak pattern (see the Supporting Information), which sometimes occurs for this class of compounds in the solid state 20. Well‐resolved spectra could be obtained for both clusters only in the liquid phase.…”

Section: Resultsmentioning

confidence: 99%

Synthesis, Characterization, and Reactivity of Functionalized Trinuclear Iron–Sulfur Clusters – A New Class of Bioinspired Hydrogenase Models

Kaiser

Knör

2015

Eur J Inorg Chem

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The air- and moisture-stable iron–sulfur carbonyl clusters Fe3S2(CO)7(dppm) (1) and Fe3S2(CO)7(dppf) (2) carrying the bisphosphine ligands bis(diphenylphosphanyl)methane (dppm) and 1,1′-bis(diphenylphosphanyl)ferrocene (dppf) were prepared and fully characterized. Two alternative synthetic routes based on different thionation reactions of triiron dodecacarbonyl were tested. The molecular structures of the methylene-bridged compound 1 and the ferrocene-functionalized derivative 2 were determined by single-crystal X-ray diffraction. The catalytic reactivity of the trinuclear iron–sulfur cluster core for proton reduction in solution at low overpotential was demonstrated. These deeply colored bisphosphine-bridged sulfur-capped iron carbonyl systems are discussed as promising candidates for the development of new bioinspired model compounds of iron-based hydrogenases.

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Terahertz, infrared and Raman vibrational assignments of [FeFe]-hydrogenase model compounds

Cited by 11 publications

References 58 publications

Resonance Raman Spectroscopy as a Tool to Monitor the Active Site of Hydrogenases

Resonance Raman Spectroscopy as a Tool to Monitor the Active Site of Hydrogenases

Bridging-hydride influence on the electronic structure of an [FeFe] hydrogenase active-site model complex revealed by XAES-DFT

Synthesis, Characterization, and Reactivity of Functionalized Trinuclear Iron–Sulfur Clusters – A New Class of Bioinspired Hydrogenase Models

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