2018 Fiscal Year Annual Research Report
Development of porous magnets with electron donor/acceptor metal–organic frameworks
| Project/Area Number |
17J02497
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| Research Institution | Tohoku University |
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Principal Investigator |
張 俊 東北大学, 理学研究科, 特別研究員(DC1)
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| Project Period (FY) |
2017-04-26 – 2020-03-31
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| Keywords | magnetic sponge / hydrogen bonding / electron transfer / host-guest interaction / theoretical calculation |
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| Outline of Annual Research Achievements |
The change of charge-ordered state in a strongly electron-correlated material allows a drastic, huge variation of its intrinsic physical properties. Here, we report a magnetic sponge behavior in an electron-donor (D) and -acceptor (A) assembled layered compound (D2A), which undergoes drastic charge-ordered state variations via three distinct states of two-electron transferred state (2e-I), charge-disproportionate state (1.5e-I), and one-electron transferred state (1e-I) depending on the degree of solvation. The initial desolvation process from the pristine solvated compound [{Ru2(m-FPhCO2)4}2TCNQ(OMe)2]-4DCE (1-4DCE; m-FPhCO2－ = meta-fluorobenzoate; TCNQ(OMe)2 = 2,5-dimethoxyl-7,7,8,8-tetracyanoquinodimethane; DCE = 1,2-dichloroethane) with a paramagnetic 2e-I state eventually produces the solvent-free compound 1 with a 1.5e-I state via a transient intermediate state 1-nDCE with a 1e-I state. Meanwhile, re-solvation procedures from 1 stabilize the 1e-I state of 1-nDCE, allowing switching between the 1.5e-I and 1e-I states repeating solvation/desolvation processes, as well as ferrimagnetic ordering temperatures between 30 K and 88 K, respectively. The 1e-I charge state of 1-nDCE was stabilized by host-guest hydrogen bonding that enables to suppress the electron-donation ability of D even in an identical framework structure with 1. This is a favorable example where host-guest hydrogen bonding is cooperated with charge transfer of frameworks which tunes bulk state as shown in biological systems.
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| Current Status of Research Progress |
Current Status of Research Progress
1: Research has progressed more than it was originally planned.
Reason
My research plan is to realize deliberate control of the physical properties such as magnetism and electrical conductivity via guest molecule
sorption. Last year, a layered compound (D2A)[{Ru2(m-FPhCO2)4}2TCNQ(OMe)2] (1) was synthesized, in which the 1e-I state was stabilized by host-guest hydrogen bonding between host framework and solvent that enables to suppress electron-donation ability of D in the identical framework as theoretical calculations have predicted. Meanwhile,the gas sorption isotherms were measured and the specific gases were employed to control the magnetic phases for 1.
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| Strategy for Future Research Activity |
We found several examples of magnetic sponges, for which the magnetic properties were tuned by charge state modulations accompanied with subtle structural modifications in solvation/desolvation treatments. So Is it possible to control the charge state by gases. Then, we would like to use simple ubiquitous gases such as O2, N2, and CO2 to control the magnetic phase. The gas sorption isotherms will be measured for these compounds. The crystal structures of gas-adsorbed phases will be characterized. In-situ magnetic measurement will be conducted under gases.
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