Reversible Shuttle Action upon Dehydration and Rehydration Processes in Cationic Coordinatively-Bonded (4,4) Square-Grid Nets Threaded by Supramolecular Bonded Anions, {[CuII(4,4′-bpy)2(H2O)][CuII(2-pySO3)3](NO3)}·H2O

{[CuII(4,4′-bpy)2(H2O)][CuII(2-pySO3)3](NO3)}·H2O, obtained serendipitously by the reaction of the constituents in water, consists of parallel coordinatively bonded cationic (4,4) corrugated square-grids polymer of {[CuII(4,4′-bpy)2(H2O)]2+}n threaded by π−π and H-bonded supramolecular chains of [CuII(2-pySO3)3] through the open squares. A single-crystal to single-crystal transformation takes place upon removal of the noncoordinated water by controlled heating. The resulting structure exhibits a rearrangement of the coordination of the copper atoms in the grids, where the Cu−H2O bond is elongated from 2.250(3) to 2.628(3) Å while the Cu-NO3 is shortened from 3.122(3) to 2.796(1) Å. This process is reversible as demonstrated by the single crystal structure after rehydration with corresponding bond distances of 2.224(3) and 3.152(3) Å. Such a cooperative effect may be associated with the Jahn−Teller distortion of the copper(II) ion accompanying the shuttle action of the hydrogen-bonded water and nitrate moiety.