Zn -Dipyridylamide-Based Coordination Frameworks: Structural Transformation and Anion Effect.

We have synthesized a series of 1 D double-zigzag ({[Zn(paps) (H O) ](PF ) }  (1), {[Zn(papo) (H O) ](PF ) }  (3), and {[Zn(papc) (H O) ](PF ) }  (5)) and 2 D polyrotaxane ([Zn(papc) (PF ) ]  (6)) frameworks through the reaction of Zn(PF ) 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) (PF ) ] ) and 4 ([Zn(papo) (PF ) ] ), which matched well with those of their Zn(ClO ) 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 Zn -paps and -papo with ClO anions can be also interconverted through heating and grinding in the presence of moisture, the related Zn -papc framework with ClO 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 ClO with PF , a series of Zn -papx-based frameworks can be obtained. Significantly, this indicates that a remarkable anion effect on such a novel structural transformation process has been demonstrated.