Toward a Tunable Synthetic [FeFe]-Hydrogenase H-Cluster Mimic Mediated by Perylene Monoimide Model Complexes: Insight into Molecular Structures and Electrochemical Characteristics

Abstract

The nature of the bridging dithiolate has an important role on tuning the physical and electrochemical properties of the synthetic H-cluster mimics of [FeFe]-hydrogenase and still of significant concern to scientists. In this report we describe the synthetic models of the active site of [FeFe]-hydrogenase containing perylene monoimide of peri-substituted disulfides as bridging linker. The resulting complexes were characterized by 1H and 13C­{1H} NMR and IR spectroscopic techniques, mass spectrometry, and elemental analysis as well as X-ray analysis of complex 2a. The purpose of this work was to investigate the influence of the perylene-linker on the redox potentials of the complexes and their catalytic ability in the presence of acetic acid (AcOH) by applying cyclic voltammetry. Moreover, we compare these results with different diiron hexacarbonyl complexes previously reported in the literature. As a result, we have found that the presence of the rylene-linker provides further stability for the reduced species and shifted its reduction potentials to more positive values.

Ligand effects on structural, protophilic and reductive features of stannylated dinuclear iron dithiolato complexes

“…14 For several years, extensive efforts have been devoted to designing structural and functional models so as to mimic the protonation and redox properties of the H-cluster. [15][16][17][18][19][20][21][22][23][24] These models include a variety of dithiolato ligands, μ-(SCH2)2X, in which the central atom/group X could be NR, CR2, O, S, SnR2 or (Ph)P=O ( Figure 1B). [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39] Moreover, several research groups have reported approaches for introducing strong σ-donor ligands, such as phosphines and phosphites, at the diiron core to enhance the protophilicity of the model complexes ( Figure 1B).…”

Electrochemical and Computational Insights into the Reduction of [Fe2(CO)6{µ-(SCH2)2GeMe2}] Hydrogenase H-Cluster Mimic

“…In two recent papers, we found that the introduction of the heavier group 14 atoms at the bridgehead position (Y) of [-XCH 2 YCH 2 X-] (X = S or Se and Y = GeMe 2 or SnMe 2 ) ligands results in an almost planar structure of the -SCYCS-moiety for Y = GeMe 2 (complex 1) or SnMe 2 ( Figure 1b) [35]. Our previous work showed that the electron density of the µ-S atoms increases (and, consequently, that of Fe-Fe bond) [22] on going from CMe 2 to SiMe 2 to GeMe 2 to SnMe 2 . As a consequence, protonation of the Fe-Fe bond is already possible using the moderately strong acid CF 3 CO 2 H in the case of Y = SnMe 2 and X = Se [38].…”

“…Nevertheless, several mechanisms were proposed based on EPR, Mössbauer spectroscopy, pH dependent FTIR spectro-electrochemistry, and DFT calculations [17][18][19][20]. Moreover, numerous hexacarbonyl diiron dithiolato complexes showing structures similar to the H-cluster were synthesize and characterized, and their catalytic applications were studied in detail in order to obtain a deeper insight into the electronic and structural characteristics of the [Fe 2 S 2 ] core of the H-cluster and to reach a better understanding of the factors stabilizing its rotated state [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40]. The rotated state of the H-cluster offers a vacant site ( Figure 1a) at which protons or H 2 interact in the catalytic proton reduction or H 2 oxidation [17][18][19][20].…”

Influence of bidentate phosphine ligands on the chemistry of [FeFe]‐hydrogenase model: insight into molecular structures and electrochemical characteristics

“…It is evident from Figure 4 that complex 2 exhibited two potential‐dependent catalytic processes in the vicinities of −1.70 to −2.10 V (for process I) and −2.10 to −2.40 V (for process II). In contrast, 3 showed only one catalytic process at −2.21 V. Under the same conditions, HAc (10 mM) in a CH 2 Cl 2 solution of [ n‐ Bu 4 N][PF 6 ] in the absence of complexes 2 and 3 reduced at potential near −2.56 V. [ 15,29 ] In the presence of various equivalents of HAc, the main reduction waves of both complexes, that is observed in the absence of acid, show small anodic shifts of 30–40 mV with concomitant increase of their peak currents indicating that the catalysis is occurring at these potentials ( E pc = −1.92 (process I) for 2 and at −2.21 V for 3 ) as shown in Figure 4. In addition, complex 2 showed another catalytic process (process II) at which a further reduction step took place, which then followed by a protonation step that lead to the formation of H 2 .…”