Zn^II–Dipyridylamide‐Based Coordination Frameworks: Structural Transformation and Anion Effect

Abstract

We have synthesized a series of 1 D double‐zigzag ({[Zn(paps)2(H2O)2](PF6)2}n (1), {[Zn(papo)2(H2O)2](PF6)2}n (3), and {[Zn(papc)2(H2O)2](PF6)2}n (5)) and 2 D polyrotaxane ([Zn(papc)2(PF6)2]n (6)) frameworks through the reaction of Zn(PF6)2 with dipyridylamide ligands (N,N′‐bis(pyridylcarbonyl)‐4,4′‐diaminodiphenyl thioether (paps), N,N′‐bis(pyridylcarbonyl)‐4,4′‐diaminodiphenyl ether (papo), and N,N′‐(methylenedi‐p‐phenylene)bispyridine‐4‐carboxamide (papc), respectively), and their molecular structures have been determined through X‐ray diffraction studies. From the powder X‐ray diffraction (PXRD) experiments, it is found that on heating, the double‐zigzag frameworks 1 and 3 undergo structural transformation to give the respective polyrotaxane frameworks 2 ([Zn(paps)2(PF6)2]n) and 4 ([Zn(papo)2(PF6)2]n), which matched well with those of their Zn(ClO4)2 analogues. Furthermore, grinding the solid samples of 2 and 4 in the presence of moisture resulted in total conversion back to the double‐zigzag frameworks 1 and 3, respectively. Although the 1 D double‐zigzag and 2 D polyrotaxane frameworks of ZnII‐paps and ‐papo with ClO4− anions can be also interconverted through heating and grinding in the presence of moisture, the related ZnII‐papc framework with ClO4− can only undergo a structural transformation process through heating. Surprisingly, reversible structural transformation between 5 and 6 has been proven successfully. In this work, we show that by replacing ClO4− with PF6−, a series of ZnII‐papx‐based frameworks can be obtained. Significantly, this indicates that a remarkable anion effect on such a novel structural transformation process has been demonstrated.

Synthesis, crystal structures and vapor adsorption properties of mercury(II) coordination polymers derived from two dipyridylamide ligands

“…In recent years, dipyridylamide ligands have proven to be excellent building blocks for the construction of novel supramolecular architectures and promising candidates for metallo-anion receptors. [19][20][21] Coordination polymers with organic ligands based on dipyridylamide moieties reveal that dipyridyl groups are good choice for connecting metal centers and the hydrogen bonding of amide functionality can add extra dimensionality to the resulted structures. [22,23] Several beautiful examples have been reported recently and further demonstrate the potential in the organization of the primary molecules in the solid state.…”

“…Among these, the choice of the bridging ligands is one of the most important aspects in the assembly of coordination polymers because the number of the donors, the molecular flexibility and the conformation of the ligands greatly affect the coordination modes between the ligand and the central metal. In recent years, dipyridylamide ligands have proven to be excellent building blocks for the construction of novel supramolecular architectures and promising candidates for metallo‐anion receptors [19–21] . Coordination polymers with organic ligands based on dipyridylamide moieties reveal that dipyridyl groups are good choice for connecting metal centers and the hydrogen bonding of amide functionality can add extra dimensionality to the resulted structures [22,23] .…”