[FeFe]-Hydrogenase H-cluster mimics mediated by naphthalene monoimide derivatives of peri-substituted dichalcogenides

Abstract

Synthetic models of the active site of [FeFe]-hydrogenase containing naphthalene monoimide (NMI) of peri-substituted dichalcogenides as bridging linkers have been prepared and characterized using different spectroscopic methods. The influence of the imide functionality and the chalcogen atoms on the redox properties and the catalytic behaviour of complexes 7-10 was studied using cyclic voltammetry. The results revealed that the imide functionality has improved the chemical stability of the reduced species and the replacement of the S atoms by Se caused a cathodic shift in the oxidation peaks. Moreover, the optical properties of compounds 1, 2, 4, and 5 and the respective diiron complexes 7-10 were investigated by UV-Vis absorption and fluorescence spectroscopy assisted by quantum chemical simulations. The structures of complexes 6-9 were confirmed by X-ray diffraction analysis.

[FeFe]‐Hydrogenase Models Containing Long Diselenolato Linkers

“…The Fe−Fe bond lengths of 1 c and 1 d (2.5475(5) and 2.5432(4) Å, respectively) are comparable to those observed in the literature . The average Fe‐CO bond length in 1 c and 1 d (1.792 and 1.795 Å) is slightly shorter than those observed in the corresponding dithiolate analogues due to less metal to CO back donation in the case of the dithiolate complexes compared to the diselenolate analogues ,. Moreover, it is clear from the torsion angle ( τ =13.59° of 1 c , 30.58° of 1 d ), formed from the intersection between (O)C−Fe‐Fe−C(O) that the steric characteristics of the linkers distort the symmetry of the Fe(CO) 3 portion of the molecule.…”

“…In addition, the normalized current function of the reduction of complexes 1 a and 1 b is almost half that of complexes 1 c and 1 d . Upon initiating the electrochemical scan in the positive direction of complexes 1 a‐d , an irreversible oxidation peak is observed for each complex (Table ) which could be assigned to the one‐electron oxidation process of Fe I Fe I → Fe I Fe II as previously reported for various diiron complexes . The potentials for oxidation of 1 a‐d are independent of increasing the carbon atoms of the chain linker of these complexes.…”

“…The latter features a bridging azadithiolato ligand as well as three CO and two CN − ligands . Over the past decade, studies on mimicking [FeFe]‐hydrogenase have been carried out mostly on altering the bridge in [Fe 2 (CO) 6 { μ ‐S(bridge)S}] and testing the resulted models as electrocatalysts . In addition, substitution of the CO ligands in [Fe 2 (CO) 6 { μ ‐S(bridge)S}] by cyanide, phosphanes, phosphites or carbenes to produce mono‐, di‐, tri‐, or tetrasubstituted complexes has been extensively studied .…”

Synthesis and Electrochemical Investigation of Mono‐ and Di‐phosphite substituted [FeFe]‐Hydrogenase H‐Cluster Mimics

“…Over the past few decades, many model complexes, which mimic the H‐cluster have been synthesized, characterized, and their catalytic applications have been studied in detail . One of the primary things to focus on these synthetic models is the enhancement of the electron density at the iron cores, which in turn leads to increase their ability to produce H 2 .…”

[FeFe]‐hydrogenase H‐cluster mimics mediated by mixed (S, Se) and (S, Te) bridging moieties: Insight into molecular structures and electrochemical characteristics

“…The active site of this system contains an organometallic Fe/S cluster, the so‐called H‐cluster (Figure A), that is, responsible for the hydrogen evolution reaction . Over the past few decades, several diiron dithiolato complexes that mimic the butterfly [Fe 2 S 2 ] sub‐unit of the H‐cluster have been synthesized and tested as electrocatalysts . Moreover, these complexes have been modified to contain heavier chalcogen donor atoms such as selenium or tellurium instead of sulfur .…”