The reduction potentials for two Wurster's crowns, aza crown ethers which incorporate the redox active N,N,N′,N′-tetraalkyl-1,4- phenylenediamine into the structure of 18-crown-6, were studied in the presence of the siderophore ferrioxamine B, FeHDFB+. Addition of FeHDFB + resulted in a positive shift in the host reduction potential for both aza crown ethers studied. This shift is explained in terms of host-guest supramolecular assembly formation, which was independently verified by FAB-MS. An enhanced affinity for host-guest formation of the reduced aza crown ether was calculated for each aza crown ether-siderophore assembly using a thermochemical cycle. These differences in host binding affinity as a function of redox state can be harnessed for use in specific metal ion compartmentalization with application, for example, to environmental remediation. © 2010 Elsevier B.V. All rights reserved.