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

Article abstract of DOI:10.1016/j.tet.2016.08.001

A series of three structurally related mono-, bidentate and macrocyclic TTF-pyridine hosts were prepared and titrated with several metal cations including Ag⁺and Pb²⁺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 Pb²⁺, 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 Pb²⁺. The bidentate host, on the other hand, is of a suitable size for Pb²⁺.