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RESEARCH PRODUCT

Structural, magnetic and calorimetric studies of a crystalline phase of the spin crossover compound [Fe(tzpy)2(NCSe)2]

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The compound [Fe(tzpy)2(NCSe)2] (tzpy = 3-(2-pyridyl)-[1,2,3]triazolo[1,5-a]pyridine)) has been synthesized and its crystal structure, magnetic behavior and calorimetric properties investigated. Samples constituted of single crystals of [Fe(tzpy)2(NCSe) 2] display a relatively cooperative spin-state change centered at T1/2 ¿ 251.7 K with a hysteresis loop 3.5 K wide. The average enthalpy (¿H) and entropy (¿S) changes upon the spin crossover behavior (SCO) obtained from DSC measurements are 11.1 ± 0.4 kJ mol -1 and 44.5 ± 3 J K-1 mol-1, respectively. The magnetic and calorimetric data have been satisfactorily simulated using the mean-field regular solution model (Slichter-Drickamer) and the domain (Sorai-Seki) models, respectively. The crystal structure of [Fe(tzpy)2(NCSe)2] has been investigated at 120 K and 325 K where the compound is in the low-spin state and essentially in the high-spin state, respectively. The intramolecular and intermolecular structural changes associated with the spin conversion are discussed and correlated with the magnetic and calorimetric data. © 2013 This journal isThe Royal Society of Chemistry.