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The development of potent H 2 production catalysts is a key aspect in our journey toward the establishment of a sustainable carbon-neutral power infrastructure. Hydrogenase enzymes provide the blueprint for designing efficient catalysts by the rational combination of central metal core and protein scaffold-based outer coordination sphere (OCS). Traditionally, a biomimetic catalyst is crafted by including natural amino acids as OCS features around a synthetic metal motif to functionally imitate the metalloenzyme activity. Here, we have pursued an unconventional approach and implanted two distinct drug molecules (isoniazid and nicotine hydrazide) at the axial position of a cobalt core to create a new genre of synthetic catalysts. The resultant cobalt complexes are active for both electrocatalytic and photocatalytic H 2 production in near-neutral water, where they significantly enhance the catalytic performance of the unfunctionalized parent cobalt complex. The drug molecules showcased a dual effect as they influence the catalytic HER by improving the surrounding proton relay along and exerting subtle electronic effects. The isoniazid-ligated catalyst C1 outperformed the nicotine hydrazide-bound complex C2, as it produced H 2 from water (pH 6.0) at a rate of 3960 s À 1 while exhibiting Faradaic efficiency of about 90 %. This strategy opens up newer avenues of bio-inspired catalyst design beyond amino acidbased OCS features.

Strategic incorporation of neurotransmitter dopamine around a cobaloxime core revealed excellent electrocatalytic (rate 8400 s-1) and photocatalytic H2 production in neutral aqueous conditions. The influence of synthetic outer coordination sphere...

The synthesis, characterization and reactivity studies of iron(ii) complexes [Fe(PySH)](OTf), 1-(OTf)2, [Fe(PySH)](ClO), 1-(ClO4)2, and [Fe(PyS)], (2), of a 2-mercaptopyridine (PySH) ligand are discussed. The X-ray crystal structures of both 1-(OTf)2 and 1-(ClO4)2 reveal a distorted tetrahedral geometry at the iron(ii) center with identical constituents. All the pyridine nitrogen atoms are protonated and thiolate ions are coordinated to the iron(ii) center. The structure and function of complex 1-(OTf)2 or 1-(ClO4)2 resembles the active site of rubredoxin. Complex 2 has octahedral geometry at the iron(ii) center forming a 1-D coordination polymer. Complex 1-(OTf)2 exhibits a high positive redox potential (E = 0.23 V vs. Ag/AgCl) which reduces to -0.12 V in the presence of triethylamine under an inert atmosphere. This change of the redox potential is highly reversible in the presence of a weak acid such as p-toluenesulfonic acid, pTsOH. DFT studies show that the complex cation [Fe(PySH)] upon treatment with a base converts to its anionic congener, [Fe(PyS)], via the deprotonation of the pyridinium moiety. The iron(ii) complexes readily react with molecular oxygen to yield the corresponding iron(iii) complex, which rapidly decays to form pyridine disulphide (PyS) and an iron(ii) complex.

The strategic inclusion of nucleic bases adenine, cytosine, and thymine, in the form of outer coordination sphere, positively impacts the electro- and photocatalytic H2 production by cobaloxime cores. These cobaloxime...