A Porous Coordination Polymer Exhibiting Reversible Single-Crystal to Single-Crystal Substitution Reactions at Mn(ll) Centers by Nitrile Guest Molecules

摘要

The porous coordination polymer {[Mn(L)(H_2O)](H_2O)_(1.5)(DMF)}_n (1) containing a water molecule coordinated at the apical position of each distorted octahedral Mn(ll) center has been synthesized using the solvothermal technique by reacting Mn(NO_3)_2·4H_2O with a new flexible ligand (LH_2) having isophthalic fragment and pyridine donors at the two ends. The coordinated water molecule could be substituted by nitrile guest molecules such as acetonitrile, acrylonitrile, allylnitrile, and crotononitrile (affording compounds 2-5, respectively) without loss of crystallinity. Interestingly, compound 1 selectively captures cis-crotononitrile into its cavity from a mixture of cis and trans isomers. Hence, the cis isomer can be separated from the trans isomer. In each case, 1.5 lattice water molecules and a dimethylformamide (DMF) molecule are also simultaneously replaced by certain numbers of these guest molecules. When these first-generation compounds 2-5 are dipped in DMF at room temperature with the lid of the vial open to the atmosphere, the mother crystal 1 is regenerated in each case. Thus, all of these substitution reactions are completely reversible. Also, the first-generation compounds 2-5 can be interconverted among one another by dipping them in appropriate nitrile guests. All of these phenomena could be observed in single-crystal to single-crystal fashion.