Hammett correlations 'beyond the molecule'

Abstract

The crown ether dibenzo[24]crown-8 (DB24C8) is interpenetrated by a wide range of disubstituted dibenzylammonium cations to generate [2]pseudorotaxane complexes by virtue of, inter alia, hydrogen bonds. 1H NMR spectroscopic measurements indicate that the solution phase binding strengths of the pseudorotaxane complexes can be controlled accurately via judicious manipulation of the substituents attached to the dibenzylammonium cations' aryl rings. A linear free energy relationship (LFER) has been found to exist between the complexes' stability constants (Kas) and the Hammett substituent constants (σ). X-Ray crystallographic analyses of the pseudorotaxanes reveal that each of their discrete supramolecular units display similar solid state superstructures. However, these analyses also demonstrate that the pseudorotaxanes associate with one another, via a myriad of intersupramolecular packing motifs, to generate a wide range of novel superarchitectures.