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ZnII -Dipyridylamide-Based Coordination Frameworks: Structural Transformation and Anion Effect
Biing-Chiau Tzeng1, Chien-Ting Yeh1, Tsung-Yi Chang1
1Department of Chemistry and Biochemistry, National Chung Cheng University, 168 University Rd., Min-Hsiung, Chiayi 62102 (Taiwan R.o.C).
Chempluschem
|January 29, 2020
Summary
This study demonstrates reversible structural transformations in zinc-based coordination frameworks using hexafluorophosphate anions. Replacing perchlorate with hexafluorophosphate enables novel anion-dependent structural changes in these materials.
Area of Science:
- Coordination Chemistry
- Materials Science
- Supramolecular Chemistry
Background:
- Exploration of metal-organic frameworks (MOFs) with dynamic structural properties.
- Investigation of anion effects on the assembly and transformation of coordination polymers.
Purpose of the Study:
- To synthesize and characterize novel 1D double-zigzag and 2D polyrotaxane frameworks based on Zn(II) ions and dipyridylamide ligands.
- To investigate the structural transformations of these frameworks induced by external stimuli such as heating and moisture.
- To elucidate the role of anions, specifically hexafluorophosphate (PF6-) versus perchlorate (ClO4-), in mediating these structural changes.
Main Methods:
- Synthesis of zinc(II) coordination frameworks using dipyridylamide ligands (paps, papo, papc) and Zn(PF6)2.
- Structural determination using X-ray diffraction (XRD) studies.
- Powder X-ray diffraction (PXRD) to monitor structural transformations upon heating and grinding in the presence of moisture.
Main Results:
- Successful synthesis of 1D double-zigzag frameworks {[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).
- Formation of 2D polyrotaxane framework [Zn(papc)2(PF6)2]n (6).
- Heating of frameworks 1 and 3 induced transformation to polyrotaxane frameworks 2 and 4, respectively.
- Grinding of polyrotaxane frameworks 2 and 4 with moisture reverted them to double-zigzag frameworks 1 and 3.
- Demonstrated reversible structural transformation between frameworks 5 and 6.
- Highlighted a significant anion effect, with PF6- enabling reversible transformations not observed with ClO4- in some cases.
Conclusions:
- A series of Zn(II)-based 1D and 2D coordination frameworks were successfully synthesized and structurally characterized.
- Reversible structural transformations between double-zigzag and polyrotaxane architectures were achieved, modulated by temperature and moisture.
- The choice of anion (PF6- vs. ClO4-) plays a crucial role in directing the type and reversibility of structural transformations in these Zn(II) frameworks.
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