Ovchinnikov ferromagnet

Finally, synthetic metals made of polymeric organic molecules may also show the property of ferromagnetism. Organic materials of this kind were first demonstrated in 1987 by Ovchinnikov and his co-workers at the Institute of Chemical Physics in Moscow. The polymer they used was based on a polydiacetylene backbone, which contains alternating double-single and triple-single bonds between the carbon atoms of the molecule (10.2). 

Ovchinnikov s proposal on the basis of valence bond theory had predicted that polyacetylene carrying phenoxy radicals as pendants 92a (X = H) might become an organic ferro-magnet.63a Several attempts to synthesize 92a had failed previously, largely due to recombination and/or disproportionation reactions.64 In relation to their studies of organic ferromagnets, Iwamura and coworkers have synthesized and studied the photolysis of AT-(phenoxy-carbonyloxy)-2-thio-... 

The possibility that poly(phenylacetylenes) with a radical on each pendant group become polymer ferromagnets was suggested by Ovchinnikov and coworkers. To examine this proposal, several research groups have synthesized such polymers , some of which indeed contain considerable amounts of radicals. Ferromagnetism, however, has not been observed. 

Pet] Petrakovskiy, G.A., Loseva, G.V., Sokolovich, V.V., Ikonnikov, V.P., Baranov, A.V., Ovchinnikov, S.G., High-Temperature Ferromagnetism and die Metal-Semiconductor Transition in an Iron Chromium Thiospinel (in Russian), Zhum. Eksp. i Tear. Fiz., 79,2411-2421 (1980) (Experimental, Crys. Structure, Electr. Prop., Magn. Prop., 10)... 

Nos. 1-3, 1st April 1995, p. 1825-6 FTIR AND NIR-FT-RAMAN STUDY OF POTENTIAL MOLECULAR FERROMAGNETICS - POLY(DIACETYLENES) SUBSTITUTED WITH NITROXYL RADICALS Shchegolikhin A N Lazareva O L Ovchinnikov A A Spector V N... 

In 1987 Ovchinnikov et al. announced the discovery of the first ferromagnetic organic polymer based on polydiacetylene chain with dangling nitroxyl radicals [8,9]. The compound was obtained by bulk polymerization of stable paramagnetic biradical BlPO initiated by light. The chemical structure of this compound is shown below. 

Another key concept in this field is the so-called Ovchinnikov ferromagnet. This is a theoretical construct, shown in Figure 17.20 C, and is not really a ferromagnet. Rather, it is a polymer that shows an increase in spin multiplicity as each monomer is added. It is an innately one-dimensional system, although extensions to two and even three dimensions can be envisioned. The /non- rule nicely rationalizes this system. 

Suggest two-dimensional analogues of the Ovchinnikov ferromagnet that are expected to experience exclusively ferromagnetic coupling. 

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