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.
Inorganics 2017, 5(3), 49; https://doi.org/10.3390/inorganics5030049
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)
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.
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Keywords:
double helicate; hysteresis; spin crossover; iron; 1,2,3-triazolimine; π–π interaction
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MDPI and ACS Style
Hora, S.; Hagiwara, H. High-Temperature Wide Thermal Hysteresis of an Iron(II) Dinuclear Double Helicate. Inorganics 2017, 5, 49. https://doi.org/10.3390/inorganics5030049
AMA Style
Hora S, Hagiwara H. High-Temperature Wide Thermal Hysteresis of an Iron(II) Dinuclear Double Helicate. Inorganics. 2017; 5(3):49. https://doi.org/10.3390/inorganics5030049
Chicago/Turabian StyleHora, Shiori; Hagiwara, Hiroaki. 2017. "High-Temperature Wide Thermal Hysteresis of an Iron(II) Dinuclear Double Helicate" Inorganics 5, no. 3: 49. https://doi.org/10.3390/inorganics5030049
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