Pseudocryptand Hosts for Paraquats and Diquats

Abstract

H-bonding interaction of acidic moieties (CHOH, 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.

“Reverse” pyridyl cryptands as hosts for viologens

“…Surprisingly, however, for all of the complexes, the Δ H values correlate linearly with their Δ S values (Figure ). This has been observed for other pseudorotaxane systems as well [7],[9]…”

“…BMP32 diacid 5a was prepared as previously reported [6]. Diester 6a , diacid 6b , and diacid chloride 6c were prepared as previously reported [3d],[9] . 1 H NMR spectra were obtained on Bruker‐500 and Agilent‐NMR‐vnmrs‐400 spectrometers; 13 C NMR spectra were collected at 125 MHz and 101 MHz, respectively.…”

“…Diacid chloride 6c [9] (0.36 g, 0.55 mmol) and 2,6‐pyridinedimethanol (76.4 mg, 0.55 mmol) were dissolved separately in a minimal amount of DCM. These solutions were placed in separate syringes and added separately to DCM (700 mL) and pyridine (1 mL) via a syringe pump (1.0 mL/h).…”

Feeding a Molecular Squid: A Pliable Nanocarbon Receptor for Electron-Poor Aromatics

“…In particular, the interior of the molecular squid was expected to share some of the binding characteristics of the parent CPP and calixarene motifs, displaying an affinity for electron-deficient and positively charged π-conjugated guests. The four guests used for further study (Chart ), namely anthra­quinone (AQ), − 10-methyl­acridinium (MA + ), − diquat (DQ 2+ ), − and its phenanthroline-derived benzologue PQ 2+ , − were selected on the basis of their established utility in supramolecular chemistry. As we found, crystals of an inclusion complex could be successfully grown from a dichloromethane solution of 1 and 4 equiv of anthra­quinone (AQ) by slow diffusion of methanol vapors.…”

Herbicidal activity and molecular docking study of novel PPO inhibitors

“…J1 and different types of phenols were used as the raw materials in the preparation of intermediate J2. Subsequently, J2 was reacted with thionyl chloride in DCM to obtain the active intermediate J3 (Jones et al 2018;Urai et al 2017). J3 could be reacted directly with compound J5 without purification to obtain the final product J6 (Cui et al 2017;Meng and Szostak 2016;Wang et al 2014).…”