Abstract
Crystal structures and dynamic rearrangements of one-dimensional coordination polymers with 4,4′-dipyridylsulfide (dps) have been studied. Reaction of Ni(NO3)2·6H2O with dps in EtOH yielded [Ni(dps)2(NO3)2] ·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)2·6H2O 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)2·6H2O with dps in acetone provided [Ni(dps)(NO3)2(H2O)] ·Me2CO (4) with no channel structure. When MeOH or acetone was used as a reaction solvent, the [Ni(dps)2(NO3)2] · (guest molecule) type coordination polymer, which was observed in 1, was not formed. Nevertheless, the reaction of Ni(NO3)2·6H2O with dps in MeOH/acetone mixed solution produced [Ni(dps)2(NO3)2]·0.5(MeOH·acetone) (5), which has an isostructural Ni-dps framework to 1.
Highlights
Many studies have reported that coordination polymers, which are called metal-organic frameworks (MOFs), with channel structures, afford a variety of infinite network structures [20]
Many porous coordination polymers cannot retain their channel frameworks after the removal of included guest molecules that were incorporated in the channels when they were prepared
Reaction of Ni(NO3)2·6H2O with dps in EtOH or MeOH produced coordination polymers 1 and 2a, which were constructed by stacks of (Ni-dps2) chains. 1 had two structural phases that reversibly transformed depending on the temperature about -12 °C
Summary
Incorporation of dynamic mechanisms into the channel frameworks have attracted intense attention for the development of new functional materials [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19]. Chemical modifications of the frameworks of zeolites have yielded unique functions such as controlled release of the including guest molecules from channels [19]. Many studies have reported that coordination polymers, which are called metal-organic frameworks (MOFs), with channel structures, afford a variety of infinite network structures [20]. These compounds have been synthesized from metal sources and organic bridging ligands by a self-assembly process. We reported a new Ni coordination polymer with 4,4'-dipyridylsulfide (dps) in our previous communication [6] This compound created unique channels, which changed the channel windows responding to temperature variation.
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