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Rodríguez-Velamazán JA, Carbonera C, Castro M, et al. Two-step thermal spin transition and LIESST relaxation of the polymeric spin-crossover compounds Fe(X-py)2[Ag(CN)2]2 (X=H, 3-methyl, 4-methyl, 3,4-dimethyl, 3-Cl). Chemistry. 2010;16(29):8785-96doi: 10.1002/chem.201000433.
Rodríguez-Velamazán, J. A., Carbonera, C., Castro, M., Palacios, E., Kitazawa, T., Létard, J. F., & Burriel, R. (2010). Two-step thermal spin transition and LIESST relaxation of the polymeric spin-crossover compounds Fe(X-py)2[Ag(CN)2]2 (X=H, 3-methyl, 4-methyl, 3,4-dimethyl, 3-Cl). Chemistry (Weinheim an der Bergstrasse, Germany), 16(29), 8785-96. https://doi.org/10.1002/chem.201000433
Rodríguez-Velamazán, J Alberto, et al. "Two-step thermal spin transition and LIESST relaxation of the polymeric spin-crossover compounds Fe(X-py)2[Ag(CN)2]2 (X=H, 3-methyl, 4-methyl, 3,4-dimethyl, 3-Cl)." Chemistry (Weinheim an der Bergstrasse, Germany) vol. 16,29 (2010): 8785-96. doi: https://doi.org/10.1002/chem.201000433
Rodríguez-Velamazán JA, Carbonera C, Castro M, Palacios E, Kitazawa T, Létard JF, Burriel R. Two-step thermal spin transition and LIESST relaxation of the polymeric spin-crossover compounds Fe(X-py)2[Ag(CN)2]2 (X=H, 3-methyl, 4-methyl, 3,4-dimethyl, 3-Cl). Chemistry. 2010 Aug 02;16(29):8785-96. doi: 10.1002/chem.201000433. PMID: 20583049.
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Chemistry. 2010 Aug 02;16(29):8785-96. doi: 10.1002/chem.201000433.

Two-step thermal spin transition and LIESST relaxation of the polymeric spin-crossover compounds Fe(X-py)2[Ag(CN)2]2 (X=H, 3-methyl, 4-methyl, 3,4-dimethyl, 3-Cl).

Chemistry (Weinheim an der Bergstrasse, Germany)

J Alberto Rodríguez-Velamazán, Chiara Carbonera, Miguel Castro, Elías Palacios, Takafumi Kitazawa, Jean-François Létard, Ramón Burriel

Affiliations

  1. Instituto de Ciencia de Materiales de Aragón (ICMA), CSIC-Universidad de Zaragoza, 50009 Zaragoza, Spain. [email protected]

PMID: 20583049 DOI: 10.1002/chem.201000433

Abstract

In the series of polymeric spin-crossover compounds Fe(X-py)(2)[Ag(CN)(2))](2) (py=pyridine, X=H, 3-Cl, 3-methyl, 4-methyl, 3,4-dimethyl), magnetic and calorimetric measurements have revealed that the conversion from the high-spin (HS) to the low-spin (LS) state occurs by two-step transitions for three out of five members of the family (X=H, 4-methyl, and X=3,4-dimethyl). The two other compounds (X=3-Cl and 3-methyl) show respectively an incomplete spin transition and no transition at all, the latter remaining in the HS state in the whole temperature range. The spin-crossover behaviour of the compound undergoing two-step transitions is well described by a thermodynamic model that considers both steps. Calculations with this model show low cooperativity in this type of systems. Reflectivity and photomagnetic experiments reveal that all of the compounds except that with X=3-methyl undergo light-induced excited spin state trapping (LIESST) at low temperatures. Isothermal HS-to-LS relaxation curves at different temperatures support the low-cooperativity character by following an exponential decay law, although in the thermally activated regime and for aX=H and X=3,4-dimethyl the behaviour is well described by a double exponential function in accordance with the two-step thermal spin transition. The thermodynamic parameters determined from this isothermal analysis were used for simulation of thermal relaxation curves, which nicely reproduce the experimental data.

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