Reversible Phase Transformation and Luminescence of Cadmium(II)–Dipyridylamide‐Based Coordination Frameworks

Abstract

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. Herein, we investigated the effect of the metal (from Zn(II) to Cd(II)) on the assembly process and luminescence properties, as well as on the particularly intriguing structural transformation of a series of papx-based frameworks. In fact, the assembly behavior and luminescence properties of the Cd(II)-papx and Zn(II)-papx frameworks were really similar. However, both Zn(II)-papx (x = s, o) frameworks can perform reversible structural transformation, but only the Cd(II)-papo framework can do it. Therefore, a delicate metal effect on such a new structural transformation can be observed.

Transforming metal–organic frameworks into functional materials

“…11bottom). In the following year, the same research group reported a similar SC-SC behaviour for a transition metal-based MOF, 23 (L 19 )(OH)] at an even lower temperature (ca. 80 °C for just 4 hours).…”

“…Surprisingly these features have not been explored and reported very much. For example, in the study of the 2D [Cu 2 (L 19 19 )-(OH)] system reported above, 23 the authors indicated that the dimensionality transformation was accompanied by a significant modification of the observed magnetic properties: the increased dimensionality of [Cu 2 (L 19 )(OH)] fragmented the magnetic exchange pathways, which ultimately resulted in an overall weakening of the magnetic correlation.…”

“…Chemical modifications on MOFs in order to change their dimensionality have been known for some years. [22][23][24][25][26][27][28][29][30][31][32][33] Only in the last decade or so this process has, however, attracted the interest of scientists, with a handful of reviews on the subject being already available in the literature. 20,34 These types of transformations occur through two general pathways: (i) single-crystal-to-single-crystal (SC-SC) transformations, and (ii) transformations via MOF dissociation, usually in solution.…”

Effect of three bis-pyridyl-bis-amide ligands with various spacers on the structural diversity of new multifunctional cobalt(II) coordination polymers

“…Even small structural changes of the organic ligands such as the symmetry, length, and flexibility or functional groups can produce obvious differences in the final coordination frameworks and topological networks [9][10][11]. Therefore, much efforts have been devoted to constructing new MOCPs with diverse structures and properties through reasonably design and selection of organic bridging ligands [12][13][14].…”

ZnII–Dipyridylamide‐Based Coordination Frameworks: Structural Transformation and Anion Effect

“…This irreversible behavior may be ascribed to the greater steric crowding from the CH 2 group compared with those of the S and O atoms, making the reversible structural transformation difficult in crystal lattices. In addition, we also examined the metal effect [from Zn II to Cd II ] on such an assembly process,9c and showed that intriguing structural transformations of a series of pap x ‐based frameworks are also observed. However, neither of the Cd II ‐pap x ( x =s, c) frameworks can perform the reversible structural transformation, whereas the Cd II ‐papo framework can.…”