International Journal of Molecular Sciences, Vol.11, No.8, 2821-2838, 2010
Syntheses and Characterization of New Nickel Coordination Polymers with 4,4'-Dipyridylsulfide. Dynamic Rearrangements of One-Dimensional Chains Responding to External Stimuli: Temperature Variation and Guest Releases/Re-Inclusions
Crystal structures and dynamic rearrangements of one-dimensional coordination polymers with 4,4'-dipyridylsulfide (dps) have been studied. Reaction of Ni(NO3)(2)center dot 6H(2)O with dps in EtOH yielded [Ni(dps)(2)(NO3)(2)]center dot EtOH (1), which had channels filled with guest EtOH molecules among the four Ni(dps)(2) chains. This coordination polymer reversibly transformed the channel structure responding to temperature variations. Immersion of 1 in m-xylene released guest EtOH molecules to yield a guest-free coordination polymer [Ni(dps)(2)(NO3)(2)] (2a), which was also obtained by treatment of Ni(NO3)(2)center dot 6H(2)O with dps in MeOH. On the other hand, removal of the guest molecules from 1 upon heating at 130 C under reduced pressure produced a guest-free coordination polymer [Ni(dps)(2)(NO3)(2)] (2b). Although the 2a and 2b guest-free coordination polymers have the same formula, they showed differences in the assembled structures of the one-dimensional chains. Exposure of 2b to EtOH vapor reproduced 1, while 2a did not convert to 1 in a similar reaction. Reaction of Ni(NO3)(2)center dot 6H(2)O with dps in acetone provided [Ni(dps)(NO3)(2)(H2O)]center dot Me2CO (4) with no channel structure. When MeOH or acetone was used as a reaction solvent, the [Ni(dps)(2)(NO3)(2)]center dot(guest molecule) type coordination polymer, which was observed in 1, was not formed. Nevertheless, the reaction of Ni(NO3)(2)center dot 6H(2)O with dps in MeOH/acetone mixed solution produced [Ni(dps)(2)(NO3)(2)]center dot 0.5(MeOH center dot acetone) (5), which has an isostructural Ni-dps framework to 1.