Reversible Single-Crystal to Single-Crystal Exchange of Guests in a Seven-Fold Interpenetrated Diamondoid Coordination Polymer

A three-dimensional polymer, {[Zn(pyeb)2](DMF)(H2O)}n (1) (DMF = N,N′-dimethylformamide), has been synthesized using solvothermal reaction of Zn(NO3)2·6H2O with a linear ligand bis{4-[2-(4-pyridyl)ethenyl] benzoic acid (pyebH). It has a 7-fold interpenetrating three-dimensional (3D) diamondoid structure (dia) having 66 uninodal net with triangular channels that are filled with DMF and water as guest molecules. When a crystal of 1 is kept in acetone at RT for 12 h, all guest molecules are replaced by acetone molecules to afford the daughter product, {[Zn(pyeb)2](acetone)}n (2) in a single-crystal to single-crystal (SC-SC) transformation. When this crystal 2 is kept in acetonitrile for 12 h, a new product, {[Zn(pyeb)2](MeCN)}n (3) is formed again without losing crystallinity. Interestingly, when either 2 or 3 is kept in dry DMF for 12 h, a new compound, {[Zn(pyeb)2](DMF)}n (4) is formed. Compound 1 can be regenerated by keeping 2, 3, or 4 in aqueous DMF for 12 h at RT. All these transformations are achieved in SC-SC fashion. The compounds are characterized by X-ray crystallography, thermogravimetery, and infrared spectroscopy.