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Iron(II) Spin Crossover Complex with the 1,2,3-Triazole-Containing Linear Pentadentate Schiff-Base Ligand and the MeCN Monodentate Ligand

1
Department of Chemistry, Faculty of Education, Gifu University, Yanagido 1-1, Gifu 501-1193, Japan
2
Graduate School of Education, Gifu University, Yanagido 1-1, Gifu 501-1193, Japan
3
Department of Chemistry and Biomolecular Science, Faculty of Engineering, Gifu University, Yanagido 1-1, Gifu 501-1193, Japan
*
Author to whom correspondence should be addressed.
Crystals 2019, 9(6), 276; https://doi.org/10.3390/cryst9060276
Received: 16 May 2019 / Revised: 24 May 2019 / Accepted: 25 May 2019 / Published: 28 May 2019
(This article belongs to the Special Issue Synthesis and Applications of New Spin Crossover Compounds)
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Abstract

A mononuclear iron(II) complex bearing the linear pentadentate N5 Schiff-base ligand containing two 1,2,3-triazole moieties and the MeCN monodentate ligand, [FeIIMeCN(L3-Me-3Ph)](BPh4)2·MeCN·H2O (1), have been prepared (L3-Me-3Ph = bis(N,N′-1-Phenyl-1H-1,2,3-triazol-4-yl-methylideneaminopropyl)methylamine). Variable-temperature magnetic susceptibility measurements revealed an incomplete one-step spin crossover (SCO) from the room-temperature low-spin (LS, S = 0) state to a mixture of the LS and high-spin (HS, S = 2) species at the higher temperature of around 400 K upon first heating, which is irreversible on the consecutive cooling mode. The magnetic modulation at around 400 K was induced by the crystal-to-amorphous transformation accompanied by the loss of lattice MeCN solvent, which was evident from powder X-ray diffraction (PXRD) studies and themogravimetry. The single-crystal X-ray diffraction studies showed that the complex is in the LS state (S = 0) between 296 and 387 K. In the crystal lattice, the complex-cations and B(1)Ph4 ions are alternately connected by intermolecular CH···π interactions between the methyl group of the MeCN ligand and phenyl groups of B(1)Ph4 ions, forming a 1D chain structure. The 1D chains are further connected by P4AE (parallel fourfold aryl embrace) interactions between two neighboring complex-cations, constructing a 2D extended structure. B(2)Ph4 ions and MeCN lattice solvents exist in the spaces of the 2D layer. DFT calculations verified that the 1,2,3-triazole-containing ligand L3-Me-3Ph gives a stronger ligand field around the octahedral coordination environment of the iron(II) ion than the analogous imidazole-containing ligand H2L2Me (= bis(N,N′-2-methylimidazol-4-yl-methylideneaminopropyl)methylamine) of the known compound [FeIIMeCN(H2L2Me)](BPh4)1.5·Cl0.5·0.5MeCN (2) reported by Matsumoto et al. (Nishi, K.; Fujinami, T.; Kitabayashi, A.; Matsumoto, N. Tetrameric spin crossover iron(II) complex constructed by imidazole⋯chloride hydrogen bonds. Inorg. Chem. Commun. 2011, 14, 1073–1076), resulting in the much higher spin transition temperature of 1 than that of 2. View Full-Text
Keywords: spin crossover; linear pentadentate ligand; iron(II); mononuclear; 1,2,3-triazole; crystal structure; magnetic properties; DFT calculation; intermolecular interactions; amorphous spin crossover; linear pentadentate ligand; iron(II); mononuclear; 1,2,3-triazole; crystal structure; magnetic properties; DFT calculation; intermolecular interactions; amorphous
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Matsuyama, T.; Nakata, K.; Hagiwara, H.; Udagawa, T. Iron(II) Spin Crossover Complex with the 1,2,3-Triazole-Containing Linear Pentadentate Schiff-Base Ligand and the MeCN Monodentate Ligand. Crystals 2019, 9, 276.

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