Metastable oxidation states of tetrathiafulvalenes on the surface of liposomes.

Redox-active liposomes are prepared by the incorporation of tetrathiafulvalene-cholesterol conjugate 1 in phospholipid vesicles. The oxidation of tetrathiafulvalene (TTF) on the surface of the liposomes in aqueous solution is monitored by UV-vis spectroscopy. It is shown that metastable (TTF+˙)2π-dimers of the mono-oxidized cation radical are formed due to the high local concentration of TTF groups in the lipid membrane. These dimers can be further stabilized by the addition of cucurbit[8]uril or by reduction of the lateral mobility in the membrane by variation of the lipid composition.