Reversible phase transformation and luminescence of cadmium(II)-dipyridylamide-based coordination frameworks.

We have synthesized a series of 1D double-zigzag ({[Cd(paps)(2)(H(2)O)(2)](ClO(4))(2)}(n) (1), {[Cd(papo)(2)(H(2)O)(2)](ClO(4))(2)}(n) (3), and {[Cd(papc)(2)(H(2)O)(2)](ClO(4))(2)}(n) (5)) and 2D polyrotaxane frameworks ([Cd(papc)(2)(ClO(4))(2)](n) (6)) by the reaction of Cd(ClO(4))(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, where their molecular structures have been determined by X-ray diffraction studies. Based on the powder X-ray data (PXRD) of compound 3 and its Zn(II) analogue, heating the double-zigzag framework of compound 3 can give the polyrotaxane framework of [Cd(papo)(2)(ClO(4))(2)](n) (4) and grinding this powder sample in the presence of moisture resulted in its complete conversion back into the pure double-zigzag framework. In addition, heating the double-zigzag frameworks of compounds 1 and 5 can induce structural transformation into their respective polyrotaxanes, whereas grinding these solid samples in the presence of moisture did not lead to the formation of the double zigzags.