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Inorganics 2017, 5(3), 49; https://doi.org/10.3390/inorganics5030049

High-Temperature Wide Thermal Hysteresis of an Iron(II) Dinuclear Double Helicate

1
Graduate School of Education, Gifu University, Yanagido 1-1, Gifu 501-1193, Japan
2
Department of Chemistry, Faculty of Education, Gifu University, Yanagido 1-1, Gifu 501-1193, Japan
*
Author to whom correspondence should be addressed.
Received: 28 June 2017 / Revised: 25 July 2017 / Accepted: 25 July 2017 / Published: 28 July 2017
(This article belongs to the Special Issue Spin-Crossover Complexes)
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Abstract

Two new dinuclear iron(II) complexes (1·PF6 and 1·AsF6) of the general formula [FeII2(L2C3)2](X)4·nH2O·mMeCN (X = PF6, n = m = 1.5 for 1·PF6 and X = AsF6, n = 3, m = 1 for 1·AsF6) have been prepared and structurally characterized, where L2C3 is a bis-1,2,3-triazolimine type Schiff-base ligand, 1,1′-[propane-1,3-diylbis(1H-1,2,3-triazole-1,4-diyl)]bis{N-[2-(pyridin-2-yl)ethyl]methanimine}. Single crystal X-ray structure analyses revealed that 1·PF6 and 1·AsF6 are isostructural. The complex-cation [FeII2(L2C3)2]4+ of both has the same dinuclear double helicate architecture, in which each iron(II) center has an N6 octahedral coordination environment. Neighboring helicates are connected by intermolecular π–π interactions to give a chiral one-dimensional (1D) structure, and cationic 1D chains with the opposite chirality exist in the crystal lattice to give a heterochiral crystal. Magnetic and differential scanning calorimetry (DSC) studies were performed only for 1·AsF6, since the thermal stability in a high-temperature spin crossover (SCO) region of 1·PF6 is poorer than that of 1·AsF6. 1·AsF6 shows an unsymmetrical hysteretic SCO between the low-spin–low-spin (LS–LS) and high-spin–high-spin (HS–HS) states at above room temperature. The critical temperatures of warming (Tc↑) and cooling (Tc↓) modes in the abrupt spin transition area are 485 and 401 K, respectively, indicating the occurrence of 84 K-wide thermal hysteresis in the first thermal cycle. View Full-Text
Keywords: double helicate; hysteresis; spin crossover; iron; 1,2,3-triazolimine; π–π interaction double helicate; hysteresis; spin crossover; iron; 1,2,3-triazolimine; π–π interaction
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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Hora, S.; Hagiwara, H. High-Temperature Wide Thermal Hysteresis of an Iron(II) Dinuclear Double Helicate. Inorganics 2017, 5, 49.

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