A multifunctional smart binuclear Zn(II) complex (1) was synthesized by a simple process. 1 contains unique water pentamers in its crystals and undergoes reversible thermochromism and exciplex emission on and off during the dehydration and rehydration processes. A thermally induced redox reaction occurred in the charge transfer of complex 1 giving rise to a persistent radical species which shows fast response and high selectivity toward gaseous NH3 as a solid-state colorimetric and fluorescent bifunctional sensor.
