Adsorption/desorption of H2O and phase transition in crystals of cobalt(II) bis(tolylterpyridine) nitrate

This study reports on the multiresponsive behavior of Co(II) bis(tolylterpyridine) nitrate crystals. Each crystal contains a single Co(II) complex and can accommodate up to 4 H2O molecules per asymmetric unit. In its fully hydrated form, the crystal contains planar hexameric hydrogen-bonded H2O clusters. The adsorption and desorption of H2O occur reversibly with changes in humidity, despite the absence of extended H2O channels. Furthermore, the crystals exhibit a crystal-to-crystal thermal phase transition. The structural studies reveal the dynamic nature of these crystals, which contribute to their multiresponsive behavior.