Metal cation binding to acetylenic tetrathiafulvalene–pyridine conjugates: affinity tuned by preorganization and cavity size

Abstract A series of three structurally related mono-, bidentate and macrocyclic TTF-pyridine hosts were prepared and titrated with several metal cations including Ag + and Pb 2+ and studied using NMR- and UV–vis spectroscopy and cyclic voltammetry. For Ag + , we found an eightfold increase in binding affinity between the bidentate and macrocyclic host and conversely, for Pb 2+ , a 100-fold drop. Density functional theory (DFT) calculations support the increased binding affinity for Ag + is due to an N⋯N distance for the uncomplexed macrocycle very much suited for binding of Ag + but being too small for Pb 2+ . The bidentate host, on the other hand, is of a suitable size for Pb 2+ .