Self-Sorting: The Exception or the Rule?

Abstract

In this paper, we pose the question of whether self-sorting in designed systems is exceptional behavior or whether it is likely to become a more general phenomenon governing molecular recognition and self-assembly. To address this question we prepared a mixture comprising two of Davis' self-assembled ionophores, Rebek's tennis ball and calixarene tetraurea capsule, Meijer's ureidopyrimidinone, Reinhoudt's calixarene bis(rosette), and two molecular clips in CDCl₃ solution and observed the behavior of this ensemble by ¹H NMR. As hypothesized, high-fidelity self-sorting behavior was observed. The influence of several key variablestemperature, concentration, equilibrium constants, and the presence of competitorson the fidelity of self-sorting is described. These results show that self-sorting is neither the exception nor the rule. They suggest, however, that the subset of known molecular aggregates that exceed the criteria required for thermodynamic self-sorting is larger than previously appreciated and potentially quite broad.