“Reverse” pyridyl cryptands as hosts for viologens

Abstract

Two new cryptands, 2 and 4, were prepared from bis(m‐phenylene)‐32‐crown‐10 (BMP32) 5,5'‐diacid chloride and dibenzo‐30‐crown‐10 (DB30) 4,4'‐diacid chloride, respectively, by reaction with pyridine‐2,6‐dimethanol. The resultant cryptands 2 and 4 have the ester moieties reversed from the previously reported isomers, 1 and 3. These “reverse” cryptands display lower association constants with viologen derivatives than the original cryptands; this is rationalized by the conjugation of the ester moieties with the aromatic rings, which reduces their electron‐donating properties and offsets the increased basicity of the pyridyl nitrogen atoms. The crystal structure of the BMP32‐based cryptand 2 indeed confirms the coplanarity of the ester and aromatic moieties and indicates that, as a result, the available cavity is quite small and that the pyridyl nitrogen atom points away from the cavity.

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.…”