title: A spin transition molecular material with a wide bistability domain.
abstract: [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).
authors.affiliation: Institut für Anorganische Chemie und Analytische Chemie, Universität Mainz, Staudingerweg, Germany. garcia@chim.ucl.ac.be
authors.forename: Yann
authors.initials: Y
authors.lastname: Garcia
authors.forename: Jacques
authors.initials: J
authors.lastname: Moscovici
authors.forename: Alain
authors.initials: A
authors.lastname: Michalowicz
authors.forename: Vadim
authors.initials: V
authors.lastname: Ksenofontov
authors.forename: Georg
authors.initials: G
authors.lastname: Levchenko
authors.forename: Georges
authors.initials: G
authors.lastname: Bravic
authors.forename: Daniel
authors.initials: D
authors.lastname: Chasseau
authors.forename: Philipp
authors.initials: P
authors.lastname: Gütlich