Toward a Tunable Synthetic [FeFe]-Hydrogenase H‑Cluster Mimic Mediated by Perylene Monoimide Model Complexes: Insight into Molecular Structures and Electrochemical Characteristics Hassan Abul-Futouh, †,§,# Artem Skabeev, †,§ Davide Botteri, † Yulian Zagranyarski, ‡ Helmar Gö rls, ∥ Wolfgang Weigand, ∥ and Kalina Peneva* ,†,⊥ † Institute of Organic Chemistry and Macromolecular Chemistry, Friedrich Schiller University Jena, Lessingstrasse 8, 07743 Jena, Germany ‡ Faculty of Chemistry and Pharmacy, Sofia University “St. Kliment Ohridski”, 1 James Bourchier Avenue, Sofia 1164, Bulgaria ∥ Institute for Inorganic and Analytical Chemistry, Friedrich Schiller University Jena, Humboldt Str. 8, 07743 Jena, Germany ⊥ Friedrich Schiller University, CEEC Jena, Philosophenweg 7a, 07743 Jena, Germany # Department of Pharmacy, Al-Zytoonah University of Jordan, P. O. Box 130, Amman 11733, Jordan * S Supporting Information 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 1 H and 13 C{ 1 H} 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. ■ INTRODUCTION The tendency of finding clean and sustainable energy sources has led to interest in molecular hydrogen production for fuel. 1 In recent years, improving catalysts for producing molecular hydrogen under mild conditions has inspired the design and synthesis of different model complexes of hydrogenases. The latter is a class of metalloenzymes found in bacteria and selected archaea that catalyze both directions of the H + /H 2 couple. 2−4 These metalloenzymes can be classified into [NiFe]-hydrogenases, [FeFe]-hydrogenases and [Fe]-hydro- genases (Hmd) and among them, [FeFe]-hydrogenase has the strongest catalytic ability for molecular hydrogen production at pH = 7 and at mild reduction potentials (−0.4 V vs. NHE). 4,5 The active site for all known [FeFe]-hydrogenases consists of an “H-cluster” (Figure 1, A) that is composed of canonical [Fe 4 S 4 ]-cluster coupled to a dinuclear iron complex called the [Fe 2 S 2 ] subsite. 6 The [Fe 2 S 2 ] subsite features a bridging azadithiolato ligand as well as three CO and two CN − ligands as shown in Figure 1, A. In the past few decades, many studies have been devoted to the synthesis and characterization of the H-cluster mimics and tested as electrocatalysts. 7−9 The modifications of the bridging dithiolate linker of the synthetic H-cluster mimics play a crucial role in tuning its redox potential and the number of electrons involved in the reduction process. Received: July 1, 2018 Article pubs.acs.org/Organometallics Cite This: Organometallics XXXX, XXX, XXX-XXX © XXXX American Chemical Society A DOI: 10.1021/acs.organomet.8b00450 Organometallics XXXX, XXX, XXX−XXX Organometallics Downloaded from pubs.acs.org by UNIV OF SUNDERLAND on 09/27/18. For personal use only.