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Harnessing a Pd4 Water-Soluble Molecular Capsule as a Size-Selective Catalyst for Targeted Oxidation of Alkyl Aromatics

Year: 2024

Type: article

Abstract: High Resolution Image Download MS PowerPoint Slide Molecular hosts with functional cavities can emulate enzymatic behavior through selective encapsulation of substrates, resulting in high chemo-, regio-, and stereoselective product formation. It is still challenging to synthesize enzyme-mimicking hosts that exhibit a narrow substrate scope that relies upon the recognition of substrates based on the molecular size. Herein, we introduce a Pd 4 self-assembled water-soluble molecular capsule [ M 4 L 2 ] ( MC ) that was formed through the self-assembly of a ligand L (4′,4‴′-(1,4-phenylene)bis(1′,4′-dihydro-[4,2′:6′,4″-terpyridine]-3′,5′-dicarbonitrile)) with the acceptor cis -[(en)Pd(NO 3 ) 2 ] [en = ethane-1,2-diamine] ( M ). The molecular capsule MC showed size-selective recognition towards xylene isomers. The redox property of MC was explored for efficient and selective oxidation of one of the alkyl groups of m -xylene and p -xylene to their corresponding toluic acids using molecular O 2 as an oxidant upon photoirradiation. Employing host–guest chemistry, we demonstrate the homogeneous catalysis of alkyl aromatics to the corresponding monocarboxylic acids in water under mild conditions. Despite homogeneous catalysis, the products were separated from the reaction mixtures by simple filtration/extraction, and the catalyst was reused. The larger analogues of the alkyl aromatics failed to bind within the MC ’s hydrophobic cavity, resulting in a lower/negligible reaction outcome. The present study represents a facile approach for selective photo-oxidation of xylene isomers to their corresponding toluic acids in an aqueous medium under mild conditions.

Source: JACS Au

DOI: 10.1021/jacsau.4c00539

Authors: Valiyakath Abdul Rinshad, Medha Aggarwal, Jack K. Clegg, Partha Sarathi Mukherjee

Institutions: Indian Institute of Science Bangalore, The University of Queensland

Language: English

Topic: Supramolecular Chemistry and Complexes

Subfield: Organic Chemistry

Field: Chemistry

Domain: Physical Sciences

Open Access status: gold

Estimated APC paid: $3,500

Funders: Ministry of Education, India, Science and Engineering Research Board