Electrodriven molecular system based on tetraviologen calix[4]resorcine and dianion 1,5-bis(n-sulfonatophenyl)-3,7-diphenyl-1,5-diaza-3,7-diphosphacyclooctane

The binding of dianionic amphiphilic 1,5-bis(para-sulfonatophenyl)-3,7-diphenyl-1,5-diaza-3,7-diphosphacyclooctane (APCO2−) with amphiphilic octacationic tetra(methylviologen)calix[4]resorcine (MVCA-C108+) has been studied in aqueous DMSO solution (30 vol% DMSO/0.1 M NaCl). The complex composition is dependent on the ratio of MVCA8+:APCO2−. A 1:1 inclusive charge-transfer complex (λmax = 480 nm) is formed by mixing of equimolar amounts of MVCA8+ and APCO2−. Donor–acceptor interaction occurs at the upper rim between four viologen groups of MVCA8+ and four nitrogen- and phosphorus-centered donor moieties of APCO2−. The increase of the amount of APCO2− leads to an additional binding of two molecules of APCO2− with MVCA-C108+. The complexes aggregate with formation of insoluble precipitates. Selective reversible electroswitching from bonded to unbounded state of one of the three bonded APCO2− occurs after the electrochemical cycle reduction of MVCA-C108+ to MVCA-C104+ and reverse oxidation.