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Erbium-formate frameworks templated by diammonium cations: syntheses, structures, structural transition and magnetic
Mengyuan Li1, Bin Liu, Bingwu Wang
1Beijing National Laboratory for Molecular Sciences, State Key Laboratory of Rare Earth Materials Chemistry and Applications, College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, P. R. China.
Dalton Transactions (Cambridge, England : 2003)
|May 10, 2011
Summary
Two novel erbium formate frameworks were synthesized using templated N,N-dimethylethylenediamine cations. These distinct structures exhibit unique coordination geometries and magnetic properties, including field-dependent relaxation processes.
Area of Science:
- Inorganic Chemistry
- Materials Science
- Coordination Chemistry
Background:
- Metal-organic frameworks (MOFs) offer tunable structures and properties.
- Erbium-based materials are of interest for magnetic applications.
- Template cations significantly influence MOF topology and coordination environment.
Purpose of the Study:
- To synthesize and characterize novel erbium formate frameworks using different diamine templates.
- To investigate the structure-property relationships, focusing on coordination geometry and magnetic behavior.
- To explore the influence of template cation size and shape on framework topology.
Main Methods:
- Solvothermal synthesis using N,N'-dimethylethylenediamine (dmenH2) and N,N,N',N'-tetramethylethylenediamine (tmenH2) as templates.
- Single-crystal X-ray diffraction for structural determination.
- Magnetic susceptibility measurements (dc and ac) from 2 to 300 K.
Main Results:
- Two distinct Er-formate frameworks were obtained: a NaCl-like structure ([dmenH2][Er(HCOO)4]2, 1) and a pillared-layer structure ([tmenH2][Er(HCOO)4]2, 2).
- Erbium exhibits eight-coordination in both structures, with square antiprismatic (1) and pentagonal bipyramidal (2) geometries.
- Framework topology is dictated by the size and shape of the template cations.
- Compound 2 shows a structural phase transition around -70 °C due to template cation disorder-order transition.
- Both compounds are paramagnetic and display field-dependent ac-susceptibilities indicating complex magnetic relaxation processes, likely due to spin-lattice relaxation.
Conclusions:
- The choice of template cation is crucial in directing the self-assembly of Er-formate frameworks with different topologies.
- The distinct coordination environments around erbium ions influence the magnetic properties.
- The observed magnetic relaxation phenomena highlight the potential of these materials for magnetic applications.
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