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De novo metalloprotein design involves the construction of proteins guided by specific repeat patterns of polar and apolar residues, which, upon self‐assembly, provide a suitable environment to bind metals and produce artificial metalloenzymes. While a wide range of functionalities have been realized in de novo designed metalloproteins, the functional repertoire of such constructs towards alternative energy‐relevant catalysis is currently limited. Here we show the application of de novo approach to design a functional H₂evolving protein. The design involved the assembly of an amphiphilic peptide featuring cysteines at tandema/dsites of each helix. Intriguingly, upon Ni^IIaddition, the oligomers shift from a major trimeric assembly to a mix of dimers and trimers. The metalloprotein produced H₂photocatalytically with a bell‐shape pH dependence, having a maximum activity at pH 5.5. Transient absorption spectroscopy is used to determine the timescales of electron transfer as a function of pH. Selective outer sphere mutations are made to probe how the local environment tunes activity. A preferential enhancement of activity is observed via steric modulation above the Ni^IIsite, towards the N‐termini, compared to below the Ni^IIsite towards the C‐termini.

Strong photoinduced oxidants are important to organic synthesis and solar energy conversion, to chemical fuels or electric. For these applications, visible light absorption is important to solar energy conversion and long‐lived excited states are needed to drive catalysis. With respect to these desirable qualities, a series of five 5,6‐dicyano[2,1,3]benzothiadiazole (DCBT) dyes are examined as organic chromophores that can serve as strong photooxidants in catalytic systems. The series utilizes a DCBT core with aryl groups on the periphery with varying electron donation strengths relative to the core. The dyes are studied via both steady‐state and transient absorption and emission studies. Additionally, computational analysis, voltammetry, crystallography, and absorption spectroelectrochemistry are also used to better understand the behavior of these dyes. Ultimately, a strong photooxidant is arrived at with an exceptionally long excited state lifetime for an organic chromophore of 16 µs. The long‐lived excited state photosensitizer is well‐suited for use in catalysis, and visible light driven photosensitized water oxidation is demonstrated using a water‐soluble photosensitizer.

Hydrogenase enzymes produce H₂gas, which can be a potential source of alternative energy. Inspired by the [NiFe] hydrogenases, we report the construction of a de novo‐designed artificial hydrogenase (ArH). The ArH is a dimeric coiled coil where two cysteine (Cys) residues are introduced at tandema/dpositions of a heptad to create a tetrathiolato Ni binding site. Spectroscopic studies show that Ni binding significantly stabilizes the peptide producing electronic transitions characteristic of Ni‐thiolate proteins. The ArH produces H₂photocatalytically, demonstrating a bell‐shaped pH‐dependence on activity. Fluorescence lifetimes and transient absorption spectroscopic studies are undertaken to elucidate the nature of pH‐dependence, and to monitor the reaction kinetics of the photochemical processes. pH titrations are employed to determine the role of protonated Cys on reactivity. Through combining these results, a fine balance is found between solution acidity and the electron transfer steps. This balance is critical to maximize the production of Ni^I‐peptide and protonation of the Ni^II−H⁻intermediate (Ni−R) by a Cys (pK_a≈6.4) to produce H₂.

A series of iron polypyridyl redox shuttles were synthesized in the 2+ and 3+ oxidation states and paired with a series of wide optical gap organic dyes with weak aryl ether electron‐donating groups. High voltage dye‐sensitized solar cell (HV‐DSC) devices were obtained through controlling the redox shuttle energetics and dye donor structure. The use of aryl ether donor groups, in place of commonly used aryl amines, allowed for the lowering of the dye ground‐state oxidation potential which enabled challenging to oxidize redox shuttles based on Fe²⁺polypyridyl structures to be used in functional devices. By carefully designing a dye series that varies the number of alkyl chains for TiO₂surface protection, the recombination of electrons in TiO₂to the oxidized redox shuttle could be controlled, leading to HV‐DSC devices of up to 1.4 V.