title: Rapid cooling experiments and use of an anionic nuclear probe to sense the spin transition of the 1D coordination polymers [Fe(NH2trz)3]SnF6n x H2O (NH2trz=4-amino-1,2,4-triazole).
abstract: [Fe(NH2trz)3]SnF6n x H2O (NH(2)trz=4-amino-1,2,4-triazole; n=1 (1), n=0.5 (2)) are new 1D spin-crossover coordination polymers. Compound 2 exhibits an incomplete spin transition centred at around 210 K with a thermal hysteresis loop approximately 16 K wide. The spin transition of 2 was detected by the Mössbauer resonance of the 119Sn atom in the SnF6 (2-) anion primarily on the basis of the evolution of its local distortion. Rapid-cooling 57Fe Mössbauer and superconducting quantum interference device experiments allow dramatic widening of the hysteresis width of 2 from 16 K up to 82 K and also shift the spin-transition curve into the room temperature region. This unusual behaviour of quenched samples on warming is attributed to activation of the molecular motion of the anions from a frozen distorted form towards a regular form at temperatures well above approximately 210 K. Potential applications of this new family of materials are discussed.
authors.affiliation: Unité de Chimie des Matériaux Inorganiques et Organiques, Département de Chimie, Université Catholique de Louvain, Place L. Pasteur 1, 1348 Louvain-la-Neuve, Belgium. yann.garcia@uclouvain.be
authors.forename: Yann
authors.initials: Y
authors.lastname: Garcia
authors.forename: Vadim
authors.initials: V
authors.lastname: Ksenofontov
authors.forename: Sophie
authors.initials: S
authors.lastname: Mentior
authors.forename: Marinela M
authors.initials: MM
authors.lastname: Dîrtu
authors.forename: Christine
authors.initials: C
authors.lastname: Gieck
authors.forename: Ashis
authors.initials: A
authors.lastname: Bhatthacharjee
authors.forename: Philipp
authors.initials: P
authors.lastname: Gütlich