A CS 4 - :(RuB 3 2 + ) 2 hybrid complex as a new class of a chemosensor was prepared by an ion-exchange reaction, where CS 4 - and RuB 3 2 + were calix[4]arenetetrasulfonate and a tris(2,2'-bipyridine)ruthenium(II) dication, respectively. In the solid state, one RuB 3 2 + was shown to bury partly in the cavity of CS 4 - from the upper rim, while other RuB 3 2 + sits near the CS 4 - :RuB 3 2 + ion-pair to balance the total electric charge of the hybrid. In methanol, on the other hand, two RuB 3 2 + molecules in the hybrid complex located in the vicinity of a CS 4 - molecule at analogous microenvironments as suggested by 1 H-NMR. Spectroscopic and excited-state properties of RuB 3 2 + in the hybrid were influenced by CS 4 - through the ion-excited dipole interaction and photoinduced electron transfer quenching. In the presence of a foreign cation as a guest, the emission intensity and lifetime of RuB 3 2 + increased, demonstrating that CS 4 - :(RuB 3 2 + ) 2 hybrid complex acted as a luminescent chemosensor. The mechanism of ion recognition was discussed in terms of changes in the photophysical properties of the hybrid complex.