Synthesis and characterization of ferrocenyl-acridine dyads and their multiresponse to proton and metal cations

Two new π-conjugated linked ferrocenyl-acridine dyads, (9-ethynylferrocenyl)acridine (3a) and (1-(ferrocenylethynyl)-4-ethynylbenzenyl)-acridine (3b), have been synthesized and investigated. UV–Vis spectroscopic and electrochemical studies reveal that 3a offers stronger electronic communication between terminal subunits than the extended system 3b, as shown by a stronger and lower-energy metal-to-ligand charge transfer (MLCT) transition and a more positive redox potential. Both of 3a and 3b show multiresponse to protons and selected metal ions (M = Zn2+, Pb2+, Hg2+, Fe3+, Cr3+), with a MLCT transition shift to the lower-energy, a redox potential shift to anode, and a luminescence increasing.