Dynamics of Metal Complex Binding in Relation to Catalytic Activity and Selectivity of an Artificial Metalloenzyme

10.26434/chemrxiv.11969010.v1 ◽

2020 ◽

Author(s):

Lara Villarino ◽

Shreyans Chordia ◽

Lur Alonso-Cotchico ◽

Eswar R. Reddem ◽

Andy-Mark Thunnissen ◽

...

Keyword(s):

Catalytic Activity ◽

Metal Complex ◽

Structural Dynamics ◽

Transcriptional Regulator ◽

Single Mutation ◽

Unique Form ◽

Artificial Metalloenzyme

We present an artificial metalloenzyme based on the transcriptional regulator LmrR that exhibits a unique form of structural dynamics involving the positioning of its abiological cofactor. The position of the cofactor was found to relate to the preferred catalytic activity, which is either the enantioselective Friedel-Crafts alkylation of indoles with beta-substituted indoles or the tandem Friedel-Crafts alkylation / enantioselective protonation of indoles with alpha-substituted enones. The artificial metalloenzyme could be specialized for one of these reactions by introducing a single mutation in the protein.<br>

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Preparation of Palladium-Impregnated Ceria by Metal Complex Decomposition for Methane Steam Reforming Catalysis

Advances in Materials Science and Engineering ◽

10.1155/2017/5828067 ◽

2017 ◽

Vol 2017 ◽

pp. 1-10 ◽

Cited By ~ 3

Author(s):

Worawat Wattanathana ◽

Suttipong Wannapaiboon ◽

Chatchai Veranitisagul ◽

Navadol Laosiripojana ◽

Nattamon Koonsaeng ◽

...

Keyword(s):

Catalytic Activity ◽

Metal Complex ◽

Steam Reforming ◽

Organic Ligand ◽

Methane Steam Reforming ◽

Microwave Assisted ◽

Methane Steam ◽

Bet Specific Surface Area ◽

Ceria Catalysts

Palladium-impregnated ceria materials were successfully prepared via an integrated procedure between a metal complex decomposition method and a microwave-assisted wetness impregnation. Firstly, ceria (CeO2) powders were synthesized by thermal decomposition of cerium(III) complexes prepared by using cerium(III) nitrate or cerium(III) chloride as a metal source to form a metal complex precursor with triethanolamine or benzoxazine dimer as an organic ligand. Palladium(II) nitrate was consequently introduced to the preformed ceria materials using wetness impregnation while applying microwave irradiation to assist dispersion of the dopant. The palladium-impregnated ceria materials were obtained by calcination under reduced atmosphere of 10% H2 in He stream at 700°C for 2 h. Characterization of the palladium-impregnated ceria materials reveals the influences of the metal complex precursors on the properties of the obtained materials. Interestingly, the palladium-impregnated ceria prepared from the cerium(III)-benzoxazine dimer complex revealed significantly higher BET specific surface area and higher content of the more active Pdδ+ (δ > 2) species than the materials prepared from cerium(III)-triethanolamine complexes. Consequently, it exhibited the most efficient catalytic activity in the methane steam reforming reaction. By optimization of the metal complex precursors, characteristics of the obtained palladium-impregnated ceria catalysts can be modified and hence influence the catalytic activity.

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