1995 Fiscal Year Final Research Report Summary
DISIGN AND CONSTRUCTION OF ORGANIC FERROMAGNET AND THEIR CRYSTAL DESIGN.
| Project/Area Number |
06453037
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
Organic chemistry
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| Research Institution | HOSEI UNIVERSITY |
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Principal Investigator |
NAKAMURA Nobuo HOSEI UNIV., ENGINEERING,PROFESSOR, 工学部, 教授 (40011598)
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| Project Period (FY) |
1994 – 1995
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| Keywords | hexacarbene / nonacarbene / ethynyl ketone / phenylnitronyl nitroxide / naphthylnitronyl nitroxide / ferromagnetic interaction / x-ray crystallography / no-bond atomic distance |
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| Research Abstract |
In order to achieve an organic ferromagnet, two approaches to it were adopted ; (i) intrarmolecular approach and (ii) intermolecular one.
(i) Previous ESR studies on branched-chain hexa-and nonacarbenes, successfully generated photochemically at a cryogenic temperature from the corresponding diazo precursors, suggested their magnetic behaviors as spin-glass or super-paramagnetic. Though large scale preparations of the carbene precursors were carried out to get further insights into the phenomenon, preliminary experiments on an AC-SQUID instrument revealed that the instrumental sensitivity was quite disappointing under an extremely dilute condition which was definitely required for the carbene not to interact antiferromagnetically.
The key step for the preparation of those carbene precursors was an amine-catalyzed cyclo-trimerization reaction of ethynyl ketones, whose mechanisms were determined by the use of substituted aryl ethynyl ketones to involve aryl 2-aminoethenyl ketones.
Cyclic he
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xacarbene which might be assumed to have a partial skeleton of an ideal polycarbene with honycomb structure was successfully generated to show that the spin quantum number S is 6 as expected theoretically. This result together with those of isomeric branched-chain hexacarbenes clearly demonstrates that the spin multiplicity of the alternant hydrocarbon molecules is determined by the topological symmetry of the pi-bond sequence.
(ii) As preliminary X-ray structural analysis on (3,5-dihydroxyphenyl) nitronyl nitroxide indicated the hydroxyl group to be effective in arranging the molecules two dimentionally, syntheses, magnetic observations, and x-ray crystallographic analyzes of several (hydroxynaphthyl) nitronyl nitroxide isomers were performed along with those of the corresponding (bromophenyl)- and (bromonaphthyl) nitronyl nitroxide radicals. It was found that some of these radicals showed ferromagnetic behaviors at extreme low temperatures. Further studies on these molecules are under way. Less
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