Tetrathiafulvalene crowns: Redox-switchable ligands

A series of redox-responsive ligands that associate the electroactive tetra thiafulvalene core with polyether subunits of various lengths has been synt hesized. X-ray structures are provided for each of the free ligands, The re quisite structural criteria for reaching switchable ligands are satisfied f or the largest macrocycles, that is, planarity of the 1,1',3,3'-tetrathiafu lvalene (TTF) pi system and correctly oriented coordinating atoms. The abil ity of these ligands to recognize various metal cations as a function of th e cavity size has been investigated by various techniques (LSIMS,H-1 NMR, a nd UV/Vis spectroscopy, cyclic voltammetry). These systems exhibit an unpre cedented high coordination ability among TTF crown ethers. Their switchable ligating properties have been confirmed by cyclic voltammetry, and metal-c ation complexation has been illustrated by X-ray structures of three of the corresponding metal complexes (Pb2+, Sr2+, and Ba2+). Solid-stale structur es of these complexes display original packing modes with channel-like arra ngements.