New pentaquinone derivatives 5 and 8 having rhodamine moieties have been designed and synthesized that undergo through-bond energy transfer (TBET) in the presence of Hg2+ ions among the various cations (Cu2+, Pb2+, Fe2+, Fe3+, Zn2+, Ni2+, Cd2+, Co2+, Ag+, Ba2+, Mg2+, K+, Na+, and Li+) tested in mixed aqueous media.