简介: |
Molecular magnetism has grown as a scientific discipline that conceives, designs, synthesizes, studies and uses new molecular magnetic materials [1-6]. It strongly relies on quantum chemistry (orbitals, ligand field, exchange, anisotropy). It uses the flexibility of (supra)molecular organic and inorganic mild chemistry, to get in a rational way materials with new but predictible properties, combining the usual characteristics of molecular materials (low density, transparency, solubility, biocompatibility) with magnetism. In such a way arose a wealth of models systems [6], spin cross over systems [7], high TC molecule-based magnets [8], single molecule magnets [9] ….
Today, the discipline is moving towards the tiny (nanosciences) and to the complex (multifunctional materials, combining magnetism and another function : anisotropy, conductivity, optical activity, photoexcitation …) to get bi- or multi-functional materials [9-13]. After a very brief review of the main milestones up to the present, we shall focus on some recent results concerning (i) photomagnetic materials : how to get photomagnetic high spin molecules with a very stable metastable excited state [10] and photomagnetic magnets, cobalt-iron Prussian blue analogues, thanks to a controlled insertion of alkali cations [11] ; (ii) chiral (optically active) magnets thanks to a strict control of the chirality of each metal centre to obtain a large magnetochiral effect [12] ; (iii) single chain magnets combining magnetism and anisotropy to achieve a slow relaxation of the magnetisation [13]. We show how the difficult challenges encountered in such new fields are overcome thanks to the close cooperation of synthetic and quantum chemists and the use of an up-to date instrumentation (microSQUID, synchrotron radiation …).
References
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[2] Molecular Magnetism, K. Ito ; N. Kinoshita, Eds, G, 1998.
[3] Magnetism : Molecules to Materials ; Vol. 1-5, J.S. Miller, M. Drillon Eds, VCH, 2001-2005.
[4] Molecular Magnets, Recent Highlights ; W. Linert, M. Verdaguer Eds, Springer, Berlin, 2003.
[5] Verdaguer M., Rational design of MMM, a tribute to Olivier Kahn, Polyhedron 2001, 20, 1115.
[6] Coord. Chem. Reviews 2005, 249, Special Issue “Molecular Magnetism”.
[7] P. Gütlich, A. Hauser, H. Spiering, Angewandte Chem. 1994, 33, p.2024 ; P. Gütlich, H.A. Goodwin Eds, Spin Cross over in transition metal compounds, (Vol. I-III) Springer, Berlin, 2004.
[8] Verdaguer M. et al.; Phil. Trans. A, 1999, 357, 2959; Coord. Chem. Rev., 1999, 190, 1023; Verdaguer M., Girolami G., in ref 3, Volume V, p. 283; Garde R. et al. ; J. Am. Chem. Soc. 2002, 124, 10531 ; E. Ruiz et al.; Chemistry, a european journal 2005, 11, 2135 ; M. Verdaguer et al. ; Interface 2002, Fall 2002, 28 ; Polyhedron, 2005, 24, 2906-2908.
[9] D. Gatteschi, R. Sessoli ; Angew. Chem., Int. Ed. 2003, 42, 268 ; D. Gatteschi, R. Sessoli, J. Villain just published at Oxford University Press.
[10] Marvaud V., F. Tuyèras et al.; Chemistry, an european journal 2003, 9, 1677 ; Herrera J.M. et al. Angew. Chem. Int. Ed. 2004, 43, 5468.
[11] Bleuzen A., Escax V., Cartier dit Moulin C. et al.; J. Am. Chem. Soc. 2001, 123, 12536 ; Angew. Chem. Int. Ed., 2004, 43, 3728 ; Angew. Chem. Int. Ed., 2005, 44, 2.
[12] Andres M. et al.; Inorg. Chem. 1999, 38, 4637; 2001, 40, 4633 ; R. Clément et al. ; ref [4] p.1 ; F. Pointillart et al. Tetrahedron Assymetry, 2006, 17, 1937 ; R. Gheorghe, Train C., Rikken G. et al; work in progress.
[13] Lescouëzec R., Julve M. et al.; Angew. Chem. 2003, 42, 1483; ref [6] p.2691. |
