Tetrathiafulvalene-imine-pyridine assemblies for Pb2+ recognition

A series of donor-pi-acceptor systems incorporating a tetrathiafulvalene moiety as the donating unit have been designed and synthesized. The efficiency of the imine (-C=N-) bond as a conjugated pi-linker in promoting intramolecular charge transfer is demonstrated and supported by calculations at the B3LYP/6-31G(d,p) level of theory. This property has been explored in the case of pyridyl-substituted systems which exhibit in particular a high binding affinity and selectivity for Ph2+ (logK = 3.5 in CH2Cl2/CH3CN), as shown by UV/Vis and H-1 NMR titrations as well as by remarkable colorimetric and electrochemical signaling. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008).