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The [Fe(etz)6](BF4)2 Spin-Crossover System - Part Two: Hysteresis in the LIESST Regime

Hinek, Roland
Spiering, Hartmut
Gütlich, Philipp
Published in Chemistry. 1996, vol. 2, no. 11, p. 1435-1439
Abstract In the [Fe(etz)6](BF4)2 spincrossover system the iron(II) complexes occupy two nonequivalent lattice sites, sites A and B. Complexes on site A show a thermal high-spin (HS) low-spin (LS) transition at 105 K, whereas complexes on site B remain in the HS state down to 10 K. Complexes on both sites exhibit light-induced spin state conversions (LIESST) at 20 K: LS HS on site A with = 514.5 nm, and HS LS on site B with = 820 nm. The relaxation processes subsequent to the HS LS conversion on site B reveal a light-induced HSLS bistability for the complexes on site B at 70 K. The bistability as well as the absence of a thermal spin transition on site B are attributed to a thermal hysteresis for the B-site complexes with a critical temperature Tc77 K on heating. This hysteresis can be interpreted in terms of strong cooperative effects of elastic origin, which, in addition, cause characteristic deviations of the relaxation on site B from first-order kinetics (self-acceleration). In contrast, the HS LS relaxation at 60 K on site A after irradiation with = 514.5 nm shows an unusual self-retardation.
Keywords HysteresisIron complexesLIESSTSpin crossoverTetrazoles
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Research group Groupe Hauser
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HINEK, Roland et al. The [Fe(etz)6](BF4)2 Spin-Crossover System - Part Two: Hysteresis in the LIESST Regime. In: Chemistry, 1996, vol. 2, n° 11, p. 1435-1439. doi: 10.1002/chem.19960021116 https://archive-ouverte.unige.ch/unige:2977

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Deposited on : 2009-09-21

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