Organic ferromagnets

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). 

A new wave of interest and productive research was aroused by synthesis of tricyclic condensed derivative benzobis(l,3,2-dithiazole) (BBDTA) which was shown experimentally to afford at least three distinct oxidation states dication, radical cation, and diradical <86SM233, 86SM239). This has been helpful for developing an approach to ferromagnetic organic metals in which homomolecular stacks are formed from donor-acceptor complexes in which the donor is a triplet and the acceptor a radical ion derived from the donor <86SM233>. Initial experiments showed conductivities lO " -10 S for complexes of BBDTA radicals with TCNQ <86SM239>. 

The high stability of TATB favors its use in military and civilian applications where insensitive high explosives are required. In addition to its applications as a HE, TATB is also used to produce the important intermediate benzenehexamine which has been used in the preparation of ferromagnetic organic salts and in the synthesis of new heteropolycyclic molecule such as 1,4,5,8,9,12-hexaazatriphenyl-ene (HAT) that serves as a strong electron acceptor ligand for low-valence transition metals. 

Nakazawa, Y, Tamura, M., Shirakawa, N., Shiomi, D., Yakahishi, M., Kinoshita, M. and Ishikawa, M. (1992). Low-temperature magnetic properties of the ferromagnetic organic radical, / -nitrophenyl nitronyl nitroxide. Phys. Rev. B, 46, 8906-14. [200]... 

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. 

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