The binding of dianionic amphiphilic 1,5-bis(para-sulfonatophenyl)-3,7-diphenyl-1,5-diaza-3,7-diphosphacyclooctane (APCO(2-)) with amphiphilic octacationic tetra(methylviologen)calix[4]resorcine (MVCA-C-10(8+)) has been studied in aqueous DMSO solution (30 vol% DMSO/0.1 M NaCl). The complex composition is dependent on the ratio of MVCA(8+):APCO(2-). A 1:1 inclusive charge-transfer complex (lambda(max) = 480 nm) is formed by mixing of equimolar amounts of MVCA(8+) and APCO(2-). Donor-acceptor interaction occurs at the upper rim between four viologen groups of MVCA(8+) and four nitrogen- and phosphorus-centered donor moieties of APCO(2-). The increase of the amount of APCO(2-) leads to an additional binding of two molecules of APCO(2-) with MVCA-C-10(8+). The complexes aggregate with formation of insoluble precipitates. Selective reversible electroswitching from bonded to unbounded state of one of the three bonded APCO(2-) occurs after the electrochemical cycle reduction of MVCA-C-10(8+) to MVCA-C-10(4+) and reverse oxidation. (C) 2013 Elsevier Ltd. All rights reserved.