Vibrational analysis of the model complex (μ-edt)[Fe(CO) 3]2 and comparison to Iron-only hydrogenase

The activation scale of hydrogenase model systems

Mary Grace Ignacio Galinato, C. Matthew Whaley, Nicolai Lehnert

Research output: Contribution to journalArticle

28 Citations (Scopus)

Abstract

Research on simple [FeFe] hydrogenase model systems of type (μ-S 2R)[Fe(CO)3]2 (R = C2H4 (edt), C3H6 (pdt)) which have been shown to function as robust electrocatalysts for proton reduction, provides a reference to understand the electronic and vibrational properties of the active site of [FeFe] hydrogenases and of more sophisticated model systems. In this study, the solution and solid state Raman spectra of (μ-edt)[Fe(CO)3] 2 and of the corresponding 13CO-labeled complex are presented and analyzed in detail, with focus on the v(C=O) and v(Fe-CO)/δ(Fe-C=O) vibrational regions. These regions are specifically Important as vibrations Involving CO ligands serve as probes for the "electron richness" of low-valent transition metal centers and the geometric structures of the complexes. The obtained vibrational spectra have been completely assigned In terms of the v(C=O), v(Fe-CO), and δ(Fe-C=O) modes, and the force constants of the important C=O and Fe-CO bonds have been determined using our Quantum Chemistry Centered Normal Coordinate Analysis (QCC-NCA). In the 400-650 cm-1 region, fifteen mixed v(Fe-CO)/δ;(Fe-C=O) modes have been Identified. The most prominent Raman peaks at 454, 456, and 483 cm-1 correspond to a combination of v(Fe-CO) stretching and O(Fe-C=O) linear bending modes. The less intense peaks at 416 cm-1 and 419 cm-1 correspond to pure δ(Fe-C=O) linear bends. In the v(C=O) region, the v(C=O) normal modes at lower energy (1968 and 1964 cm-1) are almost pure equatorial (eq) v(C=O)8q stretching vibrations, whereas the remaining four v(C=O) normal modes show dominant (C=O)eq (2070 and 1961 cm-1) and (C=O) ax (2005 and 1979 cm , ax = axial) contributions. Importantly, an Inverse correlation between the f(C=O)ax/eq and f(Fe-CO) ax/eqforce constants Is obtained, in agreement with the idea that the Fe(I)-CO bond In these types of complexes is dominated by π-backdonation. Compared to the reduced form of [FeFe] hydrogenase (Hred ), the v(C=O) vibrational frequencies of (μ-edt)[Fe(CO)3]2 are higher In energy, indicating that the dinuclear Iron core In (μ-edt)[Fe(CO)3]2 is less electron rich compared to Hred in the actual enzyme. Finally, quantum yields for the photodecomposltion of (μ-edt)[Fe(CO)3]2 have been determined.

Original languageEnglish (US)
Pages (from-to)3201-3215
Number of pages15
JournalInorganic Chemistry
Volume49
Issue number7
DOIs
StatePublished - Apr 5 2010

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Hydrogenase
Carbon Monoxide
Iron
Chemical activation
activation
iron
vibration
electrocatalysts
quantum chemistry
vibrational spectra
enzymes
Vibrational spectra
electrons
transition metals
Stretching
Raman spectra
solid state
ligands
protons
energy

All Science Journal Classification (ASJC) codes

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

Cite this

@article{4bba5c9f6e4e480baeb2cafbfff091bc,
title = "Vibrational analysis of the model complex (μ-edt)[Fe(CO) 3]2 and comparison to Iron-only hydrogenase: The activation scale of hydrogenase model systems",
abstract = "Research on simple [FeFe] hydrogenase model systems of type (μ-S 2R)[Fe(CO)3]2 (R = C2H4 (edt), C3H6 (pdt)) which have been shown to function as robust electrocatalysts for proton reduction, provides a reference to understand the electronic and vibrational properties of the active site of [FeFe] hydrogenases and of more sophisticated model systems. In this study, the solution and solid state Raman spectra of (μ-edt)[Fe(CO)3] 2 and of the corresponding 13CO-labeled complex are presented and analyzed in detail, with focus on the v(C=O) and v(Fe-CO)/δ(Fe-C=O) vibrational regions. These regions are specifically Important as vibrations Involving CO ligands serve as probes for the {"}electron richness{"} of low-valent transition metal centers and the geometric structures of the complexes. The obtained vibrational spectra have been completely assigned In terms of the v(C=O), v(Fe-CO), and δ(Fe-C=O) modes, and the force constants of the important C=O and Fe-CO bonds have been determined using our Quantum Chemistry Centered Normal Coordinate Analysis (QCC-NCA). In the 400-650 cm-1 region, fifteen mixed v(Fe-CO)/δ;(Fe-C=O) modes have been Identified. The most prominent Raman peaks at 454, 456, and 483 cm-1 correspond to a combination of v(Fe-CO) stretching and O(Fe-C=O) linear bending modes. The less intense peaks at 416 cm-1 and 419 cm-1 correspond to pure δ(Fe-C=O) linear bends. In the v(C=O) region, the v(C=O) normal modes at lower energy (1968 and 1964 cm-1) are almost pure equatorial (eq) v(C=O)8q stretching vibrations, whereas the remaining four v(C=O) normal modes show dominant (C=O)eq (2070 and 1961 cm-1) and (C=O) ax (2005 and 1979 cm , ax = axial) contributions. Importantly, an Inverse correlation between the f(C=O)ax/eq and f(Fe-CO) ax/eqforce constants Is obtained, in agreement with the idea that the Fe(I)-CO bond In these types of complexes is dominated by π-backdonation. Compared to the reduced form of [FeFe] hydrogenase (Hred ), the v(C=O) vibrational frequencies of (μ-edt)[Fe(CO)3]2 are higher In energy, indicating that the dinuclear Iron core In (μ-edt)[Fe(CO)3]2 is less electron rich compared to Hred in the actual enzyme. Finally, quantum yields for the photodecomposltion of (μ-edt)[Fe(CO)3]2 have been determined.",
author = "Galinato, {Mary Grace Ignacio} and {Matthew Whaley}, C. and Nicolai Lehnert",
year = "2010",
month = "4",
day = "5",
doi = "10.1021/ic9022135",
language = "English (US)",
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pages = "3201--3215",
journal = "Inorganic Chemistry",
issn = "0020-1669",
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Vibrational analysis of the model complex (μ-edt)[Fe(CO) 3]2 and comparison to Iron-only hydrogenase : The activation scale of hydrogenase model systems. / Galinato, Mary Grace Ignacio; Matthew Whaley, C.; Lehnert, Nicolai.

In: Inorganic Chemistry, Vol. 49, No. 7, 05.04.2010, p. 3201-3215.

Research output: Contribution to journalArticle

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T1 - Vibrational analysis of the model complex (μ-edt)[Fe(CO) 3]2 and comparison to Iron-only hydrogenase

T2 - The activation scale of hydrogenase model systems

AU - Galinato, Mary Grace Ignacio

AU - Matthew Whaley, C.

AU - Lehnert, Nicolai

PY - 2010/4/5

Y1 - 2010/4/5

N2 - Research on simple [FeFe] hydrogenase model systems of type (μ-S 2R)[Fe(CO)3]2 (R = C2H4 (edt), C3H6 (pdt)) which have been shown to function as robust electrocatalysts for proton reduction, provides a reference to understand the electronic and vibrational properties of the active site of [FeFe] hydrogenases and of more sophisticated model systems. In this study, the solution and solid state Raman spectra of (μ-edt)[Fe(CO)3] 2 and of the corresponding 13CO-labeled complex are presented and analyzed in detail, with focus on the v(C=O) and v(Fe-CO)/δ(Fe-C=O) vibrational regions. These regions are specifically Important as vibrations Involving CO ligands serve as probes for the "electron richness" of low-valent transition metal centers and the geometric structures of the complexes. The obtained vibrational spectra have been completely assigned In terms of the v(C=O), v(Fe-CO), and δ(Fe-C=O) modes, and the force constants of the important C=O and Fe-CO bonds have been determined using our Quantum Chemistry Centered Normal Coordinate Analysis (QCC-NCA). In the 400-650 cm-1 region, fifteen mixed v(Fe-CO)/δ;(Fe-C=O) modes have been Identified. The most prominent Raman peaks at 454, 456, and 483 cm-1 correspond to a combination of v(Fe-CO) stretching and O(Fe-C=O) linear bending modes. The less intense peaks at 416 cm-1 and 419 cm-1 correspond to pure δ(Fe-C=O) linear bends. In the v(C=O) region, the v(C=O) normal modes at lower energy (1968 and 1964 cm-1) are almost pure equatorial (eq) v(C=O)8q stretching vibrations, whereas the remaining four v(C=O) normal modes show dominant (C=O)eq (2070 and 1961 cm-1) and (C=O) ax (2005 and 1979 cm , ax = axial) contributions. Importantly, an Inverse correlation between the f(C=O)ax/eq and f(Fe-CO) ax/eqforce constants Is obtained, in agreement with the idea that the Fe(I)-CO bond In these types of complexes is dominated by π-backdonation. Compared to the reduced form of [FeFe] hydrogenase (Hred ), the v(C=O) vibrational frequencies of (μ-edt)[Fe(CO)3]2 are higher In energy, indicating that the dinuclear Iron core In (μ-edt)[Fe(CO)3]2 is less electron rich compared to Hred in the actual enzyme. Finally, quantum yields for the photodecomposltion of (μ-edt)[Fe(CO)3]2 have been determined.

AB - Research on simple [FeFe] hydrogenase model systems of type (μ-S 2R)[Fe(CO)3]2 (R = C2H4 (edt), C3H6 (pdt)) which have been shown to function as robust electrocatalysts for proton reduction, provides a reference to understand the electronic and vibrational properties of the active site of [FeFe] hydrogenases and of more sophisticated model systems. In this study, the solution and solid state Raman spectra of (μ-edt)[Fe(CO)3] 2 and of the corresponding 13CO-labeled complex are presented and analyzed in detail, with focus on the v(C=O) and v(Fe-CO)/δ(Fe-C=O) vibrational regions. These regions are specifically Important as vibrations Involving CO ligands serve as probes for the "electron richness" of low-valent transition metal centers and the geometric structures of the complexes. The obtained vibrational spectra have been completely assigned In terms of the v(C=O), v(Fe-CO), and δ(Fe-C=O) modes, and the force constants of the important C=O and Fe-CO bonds have been determined using our Quantum Chemistry Centered Normal Coordinate Analysis (QCC-NCA). In the 400-650 cm-1 region, fifteen mixed v(Fe-CO)/δ;(Fe-C=O) modes have been Identified. The most prominent Raman peaks at 454, 456, and 483 cm-1 correspond to a combination of v(Fe-CO) stretching and O(Fe-C=O) linear bending modes. The less intense peaks at 416 cm-1 and 419 cm-1 correspond to pure δ(Fe-C=O) linear bends. In the v(C=O) region, the v(C=O) normal modes at lower energy (1968 and 1964 cm-1) are almost pure equatorial (eq) v(C=O)8q stretching vibrations, whereas the remaining four v(C=O) normal modes show dominant (C=O)eq (2070 and 1961 cm-1) and (C=O) ax (2005 and 1979 cm , ax = axial) contributions. Importantly, an Inverse correlation between the f(C=O)ax/eq and f(Fe-CO) ax/eqforce constants Is obtained, in agreement with the idea that the Fe(I)-CO bond In these types of complexes is dominated by π-backdonation. Compared to the reduced form of [FeFe] hydrogenase (Hred ), the v(C=O) vibrational frequencies of (μ-edt)[Fe(CO)3]2 are higher In energy, indicating that the dinuclear Iron core In (μ-edt)[Fe(CO)3]2 is less electron rich compared to Hred in the actual enzyme. Finally, quantum yields for the photodecomposltion of (μ-edt)[Fe(CO)3]2 have been determined.

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