A series of donor-π-acceptor systems incorporating a tetra-thiafulvalene moiety as the donating unit have been designed and synthesized. The efficiency of the imine (-C=N-) bond as a conjugated π-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 Pb2+ (log K = 3.5 in CH2Cl2/CH3CN), as shown by UV/Vis and 1H NMR titrations as well as by remarkable colorimetric and electrochemical signaling.

http://onlinelibrary.wiley.com/doi/10.1002/ejoc.200700705/full