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Pseudocryptand Hosts for Paraquats and Diquats

Pseudocryptand Hosts for Paraquats and Diquats

Jason W Jones, Terry L Price Jr, Feihe Huang, Lev Zakharov, Arnold L Rheingold, Carla Slebodnick, Harry W Gibson

J Org Chem. 2018 Jan 19;83(2):823-834.

PMID: 29272123

Abstract:

H-bonding interaction of acidic moieties (CH2OH, COOH) at the 5- and 5'-positions of bis(1,3-phenylene)-32-crown-10 (1) with di- or tritopic anions leads to enhanced formation of inclusion complexes with N,N'-dialkyl-4,4'-bipyridinium salts ("paraquats", 2); the enforced folding of the crown ethers into pseudocryptands thus leads to pseudo-pseudorotaxanes. Strikingly, in the presence of the most effective anion (trifluoroacetate, TFA), the apparent bimolecular association constants for crown-paraquat complexation increase by more than an order of magnitude and approach those for covalent cryptands derived from the crown ether. Even though they may form pseudocryptands, the picolinate, nicotinate, and isonicotinate diesters 6 of cis-(4,4')-bis(hydroxymethyl)dibenzo-30-crown-10 do not exhibit enhanced binding of either diquat or paraquat relative to the starting diol in contrast to the picolinate ester of isomeric 5,5'-bis(hydroxymethyl)bis(m-phenylene)-32-crown-10, which displayed a higher binding constant than the starting diol. The results for the analogous reverse esters 7 derived from cis-(4,4')-dicarboxydibenzo-30-crown-10 and pyridylmethanols reveal weaker complexes with diquat than the normal esters 6; however, surprisingly, two reverse esters 7 complex paraquat more strongly than isomers 6.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
ALP1673556405	SW203668 trifluoroacetate		1673556-40-5 (free base)	Price
ALP324780021	CBLC000 trifluoroacetate		324780-02-1 (free base)	Price

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