Reversible repositioning of zinc atoms within single crystals of a zinc polycarboxylate with an open-framework structure.

Upon dehydration at 220 degrees C under vacuum, an open-framework zinc tetrahydrofuran-2,3,4,5-tetracarboxylate undergoes reversible single crystal to single crystal conversion by some of the zinc atoms moving to different positions that are 3 A away. The reverse process occurs at room temperature by exposing dehydrated crystals to air.