Reactive Microporous Rare-Earth Coordination Polymers that Exhibit Single-Crystal-to-Single-Crystal Dehydration and Rehydration

Two isostructural coordination polymers of formula [Ln2(ADC)3(H2O)6]·2H2O, (ADC = acetyledicarboxylato dianion, Ln3+ = La3+ or Ce3+) have been prepared at room temperature. The structure is three-dimensional,
possessing one-dimensional channels filled with lattice and coordinated water molecules. The presence of three
water molecules in the coordination sphere of the metal creates a dense hydrogen-bonded network. The lattice water
molecules were removed from the cerium compound at 100 °C with retention of the structure. This transformation
was also possible in a crystal-to-crystal manner. The structure of the dehydrated solid was determined and found
to present only minor modifications compared to the parent structure. The departure of the coordinated water
molecules is carried out in three steps, with retention of the structure up to 150 °C. Beyond this temperature,
dehydration is accompanied by polymerization, due to the existence of an infinite chain of short acetylene−acetylene
contacts.