A-Nitronyl nitroxides

Figure 5. Nitroxide radicals and their SOMO (a) nitronyl nitroxide and (b) imino nitroxide.

Bonnet, M., Luneau, D., Ressouche, E. et al. (1995) The experimental spin density of two nitro-phenyl nitroxides a nitronyl nitroxide and an imino nitroxide, Mol. Cryst Liqu. Cryst, 271-272, 35-53. 

Zheludev, A., Baron, V., Bonnet, M. et al. (1994) Spin density in a nitronyl nitroxide free radical. Polarized neutron diffraction investigation and ab initio calculation, J. Am. Chem. Soc., 116, 2019-2027. 

The first experimental confirmation of Glauber s prediction was shown with the material Co(hfac)2(NITPhOMe), based on a nitronyl nitroxide radical (Caneschi et al, 2001). Co(hfac)2(NITPhOMe) consists of alternating Co(hfac)2 and radical moieties arranged in ID arrays with a helical structure, and crystallizes in the P3i space group with a = b = 1.129 nm and c = 2.057 nm. A detail of the chain structure is depicted in Fig. 6.21. 

Imai and co-workers (301-303) were the first to use the [Ni(dmit)2 system in combination with a cation radical of a-nitronyl nitroxide, namely, p-lV-ethyl-pyridinium a-nitronyl nitroxide (p-EPYNN) (Scheme 15). The (p-EPYNN)-[Ni(dmit)2] compound is obtained by metathesis reaction between p-EPYNN.I and (n-Bu4N)[Ni(dmit)2] in acetonitrile. It crystallizes in the triclinic system, space group PI with a = 11.647(4), b= 11.986(3), c= 12.047(6) A,... 

Benelli, C., Caneschi, A., Gatteschi, D., and Sessoh, R. (1992) Magnetic ordering in a molecular material containing dysprosium(III) and a nitronyl nitroxide. Advanced Materials, 4, 504—505. 

Allemand, P. M., Fite, C., Srdanov, G., Keder, N., Wudl, F. and Canfield, P. (1991). On the complexities of short-range ferromagnetic exchange in a nitronyl nitroxide. Synthetic Metals, 41-43, 3291-5. [201]... 

Veciana, J., Cirujeda, J., Rovira, C., Molins, E. andNovoa, J. J. (1996). Organic ferro-magnets. Hydrogen bonded supramolecular magnetic organizations derived from hydroxylated phenyl a-nitronyl nitroxide radicals. J. Phys. I Ft, 6, 1967-86. [201] Venkatesan, K. and Ramamurthy, V. (1991). Bimolecular photoreactions in crystals. In Photochemistry in organized and constrained media (ed. V. Ramamurthy), pp. 133-84. VCH Publishers, Weinheim. [236]... 

Figure 1. Chemical structure of a nitronyl nitroxide radical, where R is the substituent that differentiates among members of this family (representative cases range from a simple H atom up to substituted six-membered rings).

Besides the electrical conductivity, a number of other applications of [M(dmit)2] have been investigated. For example, molecular-based magnets, such as the spin ladder compound p-EPYNN][Ni(dmit)2] [p-FFYNN]" " = p-N-ethylpyridinium a-nitronyl nitroxide) was reported in 1996. In the crystal, the radical cationic molecules, p-EPYNN, form one-dimensional chains with ferromagnetic interactions, while the chains of [Ni(dmit)2] monovalent anions, in a ladder formation, exhibit antiferromagnetic interactions. The magnetisation is explained by the sum of them. 

Fig. 4 General chemical structure of the family of a-nitronyl nitroxides and a representation of their singly occupied molecular orbitals (SOMO). Reprinted from ref 55 [AmabUino DB, Cirujeda 1, Veciana J, Crystal architectures of organic molecular-based magnets , (1999) Phil Trans R Soc Lond A 357 2873] by permission of The Royal Society, Copyright 1999...

Minguet. M. Amabilino, D.B. Wurst, K. Veciana, J. Circular dichroism studies of crystalline chiral and achiral a-nitronyl nitroxide radicals in KBr matrix. J. Chem. Soc., Perkin Trans. 2 2001, (5), 670-676. 

Dihydro-5//-l,4-dithiepinin-2,3-dithiolate / -N-Pyridinium a-nitronyl nitroxide... 

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