Reversible photomagnetic properties of the molecular compound [{CuII(bipy)2}2{MoIV(CN)8}]·9H2O·CH3OH

Corine Mathonière (1) , Hirokazu Kobayashi (2) , Rémy Le Bris (1) , Abdellah Kaiba (1) , Isabelle Bord (3)

1 ICMCB - Institut de Chimie de la Matière Condensée de Bordeaux
2 Faculty of Engineering
3 IMS - Laboratoire de l'intégration, du matériau au système

The optical and photomagnetic properties of [{CuII(bipy)2}2{MoIV(CN)8}]·9H2O·CH3OH (1) have been reinvestigated. A comparison between spectra in solution and in the solid state revealed the presence of an intervalence band (or Metal–Metal Charge Transfer, hereafter noted MMCT) at 570 nm. The photomagnetic properties have been performed in a Superconducting QUantum Interference Device at 10 K with irradiation in the range of the MMCT: 488 nm, 520 nm and 647 nm at 10 K. An important increase of the magnetic signal has been measured after 1 h of irradiation at 488 nm, whereas a weaker increase has been obtained for the irradiation at 520 nm in the same conditions. Moreover, after an excitation at 488 nm, an irradiation at 647 nm has induced a decrease of the magnetic moment, which corresponds to a partial deexcitation. The complete characterization of the photoproduct has been realised after an irradiation of 4 h at 488 nm. The photomagnetic properties have shown an increase of the paramagnetism of 1 at low temperature. After a thermal heating at 300 K, the material goes back to its initial state before irradiation. It is the first time that a fully reversible photomagnetic behaviour for the compound [{CuII(bipy)2}2{MoIV(CN)8}]·9H2O·CH3OH has been described. The observed properties have been discussed in terms of an electron transfer mechanism Mo → Cu.

Mots clés: Photomagnetism; Coordination compounds; Octacyanomolybdate; Electron transfer; Magnetism

Domaines: Matériaux

Corine Mathonière, Hirokazu Kobayashi, Rémy Le Bris, Abdellah Kaiba, Isabelle Bord. Reversible photomagnetic properties of the molecular compound [{CuII(bipy)2}2{MoIV(CN)8}]·9H2O·CH3OH. Comptes Rendus. Chimie, 2008, 11 (6-7), pp.665-672. ⟨10.1016/j.crci.2008.01.004⟩. ⟨hal-00319954⟩