A three-pole supramolecular switch

A supramolecular system that switches reversibly, via three different state s, through electrochemical adjustment of the guest properties of tetrathiaf ulvalene (TTF) has been developed. H-1 NMR, luminescence, and absorption sp ectroscopies, in conjunction with LSI mass spectrometry, X-ray crystallogra phy, and cyclic/differential pulse voltammetries, established that the pi-e lectron-accepting (EA) tetrathiafulvalenium dication (TTF2+) binds strongly within the cavity of the pi-electron-donating (ED) macrocyclic polyether 1 ,5-dinaphtho[38]crown-10 (1/5DN38C10), generating a host-guest complex that is stabilized by, inter alia, pi-pi stacking interactions. Comparable tech niques have also demonstrated that neutral tetrathiafulvalene (TTF(0)) acts as an ED guest when it complexes with the EA tetracationic cyclophane cycl obis(paraquat-p-phenylene) (CBPQT(4+)). On the other band, the tetrathiaful valenium radical cation (TTF+.) is not bound by either of the hosts CBPQT(4 +) or 1/5DN38C10. Electrochemical experiments revealed that the three-compo nent mixture CBPQT(4+)-1/5DN38C10-TTF behaves as:a reversible three-pole su pramolecular switch, since, depending on the potential range, TTF can be (1 ) free (in the TTF+. state), (2) included within the cavity of CBPQT(4+) (a s TTF(0)), or (3) complexed with 1/5DN38C10 (in the TTF2+ state). The syste m's three-pole behavior has interesting implications in relation to the des ign of electrochromic displays and devices capable of controlling energy- o r electron-transfer processes between selected components.