TY - JOUR
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 I.
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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U2 - 10.1021/ic9022135
DO - 10.1021/ic9022135
M3 - Article
C2 - 20225804
AN - SCOPUS:77950221202
SN - 0020-1669
VL - 49
SP - 3201
EP - 3215
JO - Inorganic chemistry
JF - Inorganic chemistry
IS - 7
ER -