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Responsive Four-Coordinate Iron(II) Nodes in FePd(CN)4
Ryo Ohtani1, Hiromu Matsunari2, Takafumi Yamamoto3
1Department of Chemistry, Faculty of Science, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka, 819-0395, Japan.
Angewandte Chemie (International Ed. in English)
|July 15, 2020
Summary
Researchers synthesized a novel 3D coordination polymer (CP) featuring four-coordinate iron(II) ions, challenging previous assumptions. This discovery opens new avenues for designing advanced metal-organic frameworks with unique properties.
Area of Science:
- Materials Science
- Inorganic Chemistry
- Crystallography
Background:
- Metal node design is critical for creating diverse coordination polymers (CPs) and metal-organic frameworks (MOFs).
- Iron(II) ions (FeII) have been exclusively observed in six-coordinated states within these structures.
- Achieving lower coordination numbers for FeII is essential for developing novel materials with tunable properties.
Purpose of the Study:
- To synthesize a novel three-dimensional (3D) coordination polymer (CP) with four-coordinate FeII ions.
- To investigate the structural and coordination characteristics of the new FeII-containing CP.
- To explore the potential of the four-coordinate FeII node as a thermo-responsive element.
Main Methods:
- Synthesis of a 2D CP, Fe(H2O)2Pd(CN)4·4H2O.
- Thermal treatment to remove water molecules and induce structural transformation.
- Atomic-resolution transmission electron microscopy (TEM).
- Powder X-ray diffraction (XRD) and neutron diffraction measurements.
Main Results:
- A novel cyanide-bridged 3D CP, FePd(CN)4, was successfully synthesized.
- The structure features unprecedented four-coordinate FeII ions with an intermediate geometry between tetrahedral and square-planar.
- The FePd(CN)4 forms a two-fold interpenetrated PtS topology network.
- The four-coordinate FeII node exhibits a distorted geometry, acting as a thermo-responsive flexible node.
Conclusions:
- The study presents the first example of a 3D CP with four-coordinate FeII ions.
- The unique coordination environment of FeII enables the development of novel, flexible coordination networks.
- This work expands the possibilities for designing functional materials based on metal node engineering.
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