[FeFe]-Hydrogenase synthetic mimics based on peri-substituted dichalcogenides

[FeFe]-hydrogenase plays an important role in the microbial energy metabolism, catalysing the reduction of protons into molecular hydrogen. Herein the synthesis and the spectroscopic analysis (NMR, IR, UV/vis) of [FeFe]-complexes based on the naphtho[1,8-cd][1,2]dithiole, naphtho[1,8-cd][1,2]diselenole and naphtho[1,8-cd][1,2]thiaselenole backbone, which incorporate substituents in position 2 of the naphthalene ring (OMe, tBu) are described. Additionally, dichalcogenide-based [FeFe]-complexes, containing the rigid aromatic phenanthrene and fluorene backbones are discussed. Cyclic voltammetry was applied in order to investigate the electrochemical properties of these new [FeFe]-hydrogenase synthetic analogues. Titration with pTsOH was monitored by cyclic voltammetry and showed that these [FeFe]-complexes are catalysts for proton reduction. After having studied these promising systems for proton reduction catalysis, the functionalization of naphthalene-1,8-dithiolate and diselenolate-based [FeFe]-complexes by insertion of aromatic and alkyl amino and imino groups is described. Spectroscopic and electrochemical techniques were applied to confirm protonation of the nitrogen, upon acid addition, and the effect on proton reduction catalysis, which was remarkably improved. Following these results, the synthesis of a molecular dyad containing zinc tetraphenylporphyrin, covalently linked to naphthalene-1,8-dithiolate-based [FeFe]-complex, via amino group, is reported. The initial investigations (UV/vis and emission spectroscopy) showed catalytic photo-induced hydrogen production, which was monitored by gas chromatography