A spin transition molecular material with a wide bistability domain.

Yann Garcia (1, 2) , Jacques Moscovici (3, 4) , Alain Michalowicz (3, 4) , Vadim Ksenofontov (2) , Georg Levchenko (2) , Georges Bravic (1) , Daniel Chasseau (1) , Philipp Gütlich (2)

1 ICMCB - Institut de Chimie de la Matière Condensée de Bordeaux
2 Insitut für Anorganische und Analytische Chemie
3 Laboratoire d'Utilisation du Rayonnement Electromagnétiques
4 Physique des Milieux Denses

[Fe(hyptrz)3](4-chloro-3-nitrophenylsulfonate)22 H2O (1; hyptrz=4-(3-hydroxypropyl)-1,2,4-triazole) has been synthesized and its physical properties have been investigated by several physical techniques including magnetic susceptibility measurements, calorimetry, and Mössbauer, optical, and EXAFS spectroscopy. Compound 1 exhibits a spin transition below room temperature, together with a very wide thermal hysteresis of about 50 K. This represents the widest hysteresis loop ever observed for an FeII-1,2,4-triazole spin transition material. The cooperativity is discussed on the basis of temperature-dependent EXAFS studies and of the structural features of a CuII analogue. The EXAFS structural model of (1) in both spin states is compared to that obtained for a related material whose spin transition occurs above room temperature. EXAFS spectroscopy suggests that 1,2,4-triazole chain compounds retain a linear character whatever the spin state of the iron(II).

Mots clés: EXAFS spectroscopy; Iron; Spin crossover; 4-triazole; Chain structures

Domaines: Matériaux

Yann Garcia, Jacques Moscovici, Alain Michalowicz, Vadim Ksenofontov, Georg Levchenko, et al.. A spin transition molecular material with a wide bistability domain.. Chemistry - A European Journal, 2002, 8 (21), pp.4992-5000. ⟨10.1002/1521-3765(20021104)8:21<4992::AID-CHEM4992>3.0.CO;2-8⟩. ⟨hal-00738238⟩