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Coordination cage catalysed hydrolysis of organophosphates: cavity or surface based?

DOI: 10.1002/chem.201904708 DOI Help

Authors: Christopher Taylor (University of Warwick) , Alexander Metherell (University of Sheffield) , Stephen Argent (University of Warwick) , Fatma Ashour (University of Sheffield) , Nicholas Williams (University of Sheffield) , Michael Ward (University of Warwick)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Chemistry – A European Journal

State: Published (Approved)
Published: November 2019
Diamond Proposal Number(s): 19876

Open Access Open Access

Abstract: The hydrophobic central cavity of a water‐soluble M8L12 cubic coordination cage can accommodate a range of phospho‐diester and phospho‐triester guests such as the insecticide 'dichlorvos' (2,2‐dichlorovinyl dimethyl phosphate) and the chemical warfare agent analogue diisopropyl chlorophosphate. The accumulation of hydroxide ions around the cationic cage surface due to ion‐pairing in solution generates a high local pH around the cage, resulting in catalysed hydrolysis of the phospho‐triester guests. A series of control experiments unexpectedly demonstrates that – in marked contrast to previous cases – it is not necessary for the phospho‐triester substrates to be bound inside the cavity for catalysed hydrolysis to occur. This suggests that catalysis can occur on the exterior surface of the cage as well as the interior surface, with the exterior‐binding catalysis pathway dominating here because of the small binding constants for these phospho‐triester substrates in the cage cavity. These observations suggest that cationic but hydrophobic surfaces could act as quite general catalysts in water by bringing substrates into contact with the surface (via the hydrophobic effect) where there is also a high local concentration of anions (due to ion‐pairing / electrostatic effects).

Journal Keywords: host-guest chemistry; coordination cage; catalysis; supramolecular chemistry; phospho-esters

Subject Areas: Chemistry


Instruments: I19-Small Molecule Single Crystal Diffraction

Added On: 27/11/2019 15:39

Documents:
chem.201904708.pdf

Discipline Tags:

Physical Chemistry Catalysis Chemistry

Technical Tags:

Diffraction Single Crystal X-ray Diffraction (SXRD)