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Issue 43, 2016
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Synthesis, structure, and spin crossover above room temperature of a mononuclear and related dinuclear double helicate iron(II) complexes

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Abstract

A mononuclear iron(II) complex, [FeII(L1Me)2](PF6)2 (1), and a related dinuclear one, [FeII2(L2C2)2](PF6)4·5H2O·MeCN (2), were prepared, where L1Me is a tridentate N3 coordinating Schiff-base ligand, 1-methyl-1,2,3-triazol-4-yl-methylideneamino-2-ethylpyridine, and L2C2 is a dimeric form ligand of L1Me, 1,1′-(1,2-ethanediyl)bis-1,2,3-triazol-4-yl-methylideneamino-2-ethylpyridine, and their magnetostructural relationships were investigated. Mononuclear 1 shows a gradual one-step spin crossover (SCO) from the low-spin (LS) state (S = 0) at room temperature (RT) to the mostly high-spin (HS) state (S = 2) at 470 K spanning a temperature range of more than 170 K, while dinuclear 2 shows an anomalous two-step SCO with a gradual transition in a first step from the LS–LS state at RT to around 432 K and then an abrupt spin transition centred at 432 K with 11 K wide hysteresis in a second step (T1/2↑ = 437 K and T1/2↓ = 426 K) reaching the mostly HS–HS state. Single crystal X-ray structure analyses revealed that the iron(II) centre of mononuclear 1 has an N6 octahedral coordination environment with two tridentate L1Me ligands, while the complex-cation of 2 has a dinuclear double helicate architecture as though a dimeric form of two complex-cations of 1 replaced their methyl group with a bridging ethylene chain. Both complexes have a cationic two-dimensional (2D) structure in which the 2D layer of mononuclear 1 is constructed of intermolecular CH⋯N hydrogen bonds between adjacent complex-cations, while that of dinuclear 2 is constructed of both intermolecular π–π and CH/π interactions between neighboring helicates.

Graphical abstract: Synthesis, structure, and spin crossover above room temperature of a mononuclear and related dinuclear double helicate iron(ii) complexes

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Publication details

The article was received on 13 Jul 2016, accepted on 12 Aug 2016 and first published on 12 Aug 2016


Article type: Paper
DOI: 10.1039/C6DT02766K
Citation: Dalton Trans., 2016,45, 17132-17140
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    Synthesis, structure, and spin crossover above room temperature of a mononuclear and related dinuclear double helicate iron(II) complexes

    H. Hagiwara, T. Tanaka and S. Hora, Dalton Trans., 2016, 45, 17132
    DOI: 10.1039/C6DT02766K

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