Optically active molecule-based high temperature magnets

2017 edition

barbara rodriguez

Prussian blue (PBs) type materials are the molecule-based magnets with highest ordering  temperatures discovered up to date. These non-stoichiometric solids of general formula
AxMy[M'(CN)6].nH2O (A = alkali cation; M, M’ = transition metal), and face-centered cubic
structure, are formed by homo-or heterometalic combinations of transition metals in multiple oxidation states, bridged by cyanide ligands. Magnetic ordering critical temperatures (TC) over room temperature have been reported when Vn+and/or Crn+ are the constitutive metals, although these derivatives usually exhibit poor air stability in ambient conditions. [1,2]
In the search for chiral molecule-based magnets, a successful strategy has been implemented by the incorporation of chiral building blocks in synthesis of PB-based magnets. [3] This powerful strategy has not been so useful with the high TC counterparts, probably becasue of the instability and difficult handling of these materials and their corresponding precursors. In this communication we will report successful strategies for the preparation of high TC chiral molecule-based magnets in the PB family. For example, we have been able to synthesize a new cyanide-bridged chromium-vanadium magnet that orders above 120K, and that exhibits optical activity.

References

[1] S. Ferlay, T. Mallah, R.Ouahès, P.Veillet, and M. Verdaguer, Nature, 1995, 378, 01-702.
[2] M. Verdaguer et al. Coord. Chem. Rev., 1999, 190-192, 1023–1047.
[3] W. Kaneko, S. Kitagawa, M. Ohba, J. Am. Chem. Soc., 2007, 129, 248–249.