| Budget Amount *help |
¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 2000: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 1999: ¥2,600,000 (Direct Cost: ¥2,600,000)
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| Research Abstract |
The target of this project was the development of new single-molecule magnets based on Mn12 complexes.
1) Chemical modification of Mn12 complexes.
Mn12 complexes are known as single-molecule magnets with the highest blocking temperature. Their 16 bridging acetate groups can be replaced by other carboxylic acids. We have tried to replace the bridging acetate groups to decanoic acid, 1-adamantanecarboxylic acid, trans-3-(3-thienyl) acrylic acid, heptafluorobutanoic acid, dichloroacetic acid, and trichloroacetic acid. The ligand-exchange reactions were successful for most of ligands ; the resulting compounds retains the magnetic properties typical for single-molecule magnets. The blocking temperatures TB for them were all 2.8 K, which was a little lower than 3.0 K for the Mn12-acetate. However, the compound obtained by replacing acetate to decanoic acid showed antiferromagnetic behavior, indicating that this compound is not a single-molecule magnet.
2) Formation of charge-transfer complexes of a Mn12 complex with various donor molecules
We have tried the formation of charge-transfer complexes of a Mn12 complex with various TTF-type donor molecules. When we mixed solutions of dimethyldiphenyl-tetrathiafluvalene and Mn12-pentafluorobenzoate complex, one-electron transfer takes place to form the cationic TTF derivative and anionic Mn12 compound. By standing the methylenechloride solution with diffusion solvent for one week, reddish-black fine crystals were obtained. The solution UV-vis spectrum shows intense absorption band at around 520 nm with a molar absorption coefficient ε more than 30000, which can be attributed to the charge-transfer band between Mn12 anion and TTF-derivative cation. On the basis of solution esr, nmr and UV-vis. spectra, the formation of the charge-transfer complex occurred not immediately but rather slowly. From the magnetic susceptibility measurement, we confirmed the charge-transfer complex is a single-molecule magnet.
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