Metal–Nitroxide Complexes: Synthesis and Magnetostructural Correlations - Stable Radicals: Fundamentals and Applied Aspects of Odd-Electron Compounds - page 501

quite justified. Note that many nitroxides were specially synthesized and checked for use as contrast agents
for MRT. 270,271 However, spin labeled imidazoles bearing no charge (L 62 , Scheme 13.29) and possessing
anomalously high solubility in water and low toxicity for living organisms were found only recently. 272,273
They cannot act as effective contrast agents. It is not excluded that unification of paramagnetic metal ions
with low toxic nitroxides related to L 62 and possessing high solubility in water in a multispin complex
will afford safe contrast agents capable of giving high quality magnetic resonance images in future.

13.7 Conclusions

An analysis of the accumulated material shows that synthetic strategies and major techniques were devel-
oped for the design of high-dimensional multispin systems based on coordination compounds of transition
metals with nitroxides, exhibiting a tendency toward cooperative magnetic ordering. While 25 years ago
approaches to the design of different classes of molecular ferromagnets were still in their infancy, today
there is rich array of experimental results in this field. This fully relates to molecular magnets based on
metal-nitroxide systems, many of which can now be obtained in significant amounts in the form of stable
(under the normal conditions) large transparent single crystals. These compounds form a new class of light
and transparent magnetoactive materials. They can be obtained under mild conditions, for example, by
crystallization from solution under the normal conditions, while classic magnetic materials are generally
obtained by high temperature energy consuming processes. Prospects are now being discussed for using
molecular magnets based on metal-nitroxide complexes in various magnetic and photomagnetic devices,
data recording and magnetic visualization systems, and spintronic devices for molecular computing. It is
certainly difficult to foresee all future applications of molecular magnets. However, there is every reason
to believe that the above-mentioned unique combination of physical characteristics, which is responsible
for the specific properties of molecular magnets but not inherent in classic magnetic materials, will find
use in the near future.

References

1. S. S. Eaton and G. R. Eaton, Coord. Chem. Rev. , 26 , 207 - 262 (1978).

2. R. S. Drago, Coord. Chem. Rev. , 32 , 97 - 110 (1980).

3. Yu. Zolotov, O. M. Petrukhin, V. Yu. Nagy, and L. B. Volodarsky, Anal. Chim. Acta. , 115 , 1 - 23 (1980).

4. S. V. Larionov, in Imidazoline nitroxides. Synthesis, properties and applications , (ed. L. B. Volodarsky), CRC

Press, Inc., Boca Raton, Vol. 2, 81 - 113 (1988).

5. S. S. Eaton and G. R. Eaton, Coord. Chem. Rev. , 83 , 29 - 72 (1988).

6. A. Caneschi., D. Gatteschi, and P. Rey, Prog. Inorg. Chem. , 39 , 331 - 429 (1991).

7. O. Kahn, Molecular magnetism , VCH, New York, 1993.

8. L. B. Volodarsky, V. A. Reznikov, and V. I. Ovcharenko, Synthetic chemistry of stable nitroxides , CRC Press,

Inc., Boca Raton, 1994.

9. G. A. Abakumov, Journal of VCO Mendeleeva , 24 , 156 - 160 (1979).

10. V. I. Ovcharenko and R. Z. Sagdeev, Russian Chemical Reviews , 68 (5), 345 - 363 (1999).

11. H. Iwamura, K. Inoue, and T. Hayamizu, Pure Appl. Chem. , 68 , 243 - 252 (1996).

12. V. I. Ovcharenko, K. Yu. Maryunina, S. V. Fokin, et al ., Rus. Chem. Bull. , 53, 2406 -2427 (2004).

13. D. Luneau and P. Rey, Coord. Chem. Rev. , 249 , 2591 - 2611 (2005).

14. D. Luneau, A. Borta, Y. Chumakov, et al ., Inorg. Chim. Acta , 361 , 3669 -3676 (2008).

15. A.Caneschi,D.Gatteschi,R.Sessoli,andP.Rey, Acc. Chem. Res. 22, 392 -398 (1989).

16. H. Iwamura and K. Inoue, in Magnetism: Molecules to Materials II. Molecule-Based Materials , (eds J. S. Miller

and M. Drillon), Wiley - VCH Verlag GmbH & Co. KGaA, Weinheim, 2001, pp. 61 - 108.