Spin-crossover in a trans-[FeL2(NCS)2] family (L = triaryltriazole): remote substituent effects on spin transition modes and temperature

Guo-Ping Shen; Li Qi; Lei Wang; Yan Xu; Jing-Jing Jiang; Dunru Zhu; Xiao-Qin Liu; Xiaozeng You

doi:10.1039/C3DT50821H

Spin-crossover in a trans-[FeL₂(NCS)₂] family (L = triaryltriazole): remote substituent effects on spin transition modes and temperature†

Guo-Ping Shen,^a Li Qi,^a Lei Wang,^a Yan Xu,^a Jing-Jing Jiang,^a Dunru Zhu,*^ab Xiao-Qin Liu^a and Xiaozeng You^b

* Corresponding authors

^a State Key Laboratory of Materials-oriented Chemical Engineering, College of Chemistry and Chemical Engineering, Nanjing University of Technology, Nanjing 210009, China
E-mail: zhudr@njut.edu.cn
Fax: +86 25 83172261
Tel: +86 25 83587717

^b State Key Laboratory of Coordination Chemistry, Nanjing National Laboratory of Microstructures, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, China

Abstract

We report the syntheses, characterisations, and spin-crossover behaviours of four mononuclear trans-[Fe(L1–L4)₂(NCS)₂] complexes (L = 4-(p-R₁-phenyl)-3,5-bis(2-pyridyl)-4H-1,2,4-triazole and 4-(p-methylphenyl)-3-(p-R₂-phenyl)-5-(2-pyridyl)-4H-1,2,4-triazole, (1) R₁ = Cl (L1); (2) R₁ = Me (L2); (3) R₂ = MeO (L3); (4) R₂ = F (L4)). The X-ray single crystal structural analysis reveals that 1 and 2 crystallize in the triclinic space group P [1 with combining macron] , whereas 3·0.5H₂O and 4 crystallize in the monoclinic space group P2₁/c, and all complexes possess a similar distorted [FeN₆] octahedron with two trans-positions NCS⁻ anions. Changing of the distal substituent on the phenyl ring of the triaryltriazoles causes differences in the crystal packing of the complexes that are key to their magnetic properties. Magnetic measurements indicate that 1 shows an abrupt transition with T_1/2 = 235 K, 2 displays a 3 K hysteresis loop with T_1/2^↓ = 217 K and T_1/2^↑ = 220 K, 3 exhibits a gradual spin transition with T_1/2 = 156 K and 4 undergoes an incomplete (70%) spin transition with T_1/2 = 97 K. The substituted group effects and intermolecular interactions appear to be critical to spin transition modes and temperature in this family.

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Article information

DOI: https://doi.org/10.1039/C3DT50821H
Article type: Paper
Submitted: 27 Mar 2013
Accepted: 29 Apr 2013
First published: 01 May 2013

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Dalton Trans., 2013,42, 10144-10152

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Spin-crossover in a trans-[FeL₂(NCS)₂] family (L = triaryltriazole): remote substituent effects on spin transition modes and temperature

G. Shen, L. Qi, L. Wang, Y. Xu, J. Jiang, D. Zhu, X. Liu and X. You, Dalton Trans., 2013, 42, 10144 DOI: 10.1039/C3DT50821H

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