Substituent dependence on the spin crossover behaviour of mononuclear Fe(ii) complexes with asymmetric tridentate ligands

Ryo Saiki; Haruka Miyamoto; Hajime Sagayama; Reiji Kumai; Graham N Newton; Takuya Shiga; Hiroki Oshio

doi:10.1039/c9dt00204a

Substituent dependence on the spin crossover behaviour of mononuclear Fe(ii) complexes with asymmetric tridentate ligands

Dalton Trans. 2019 Mar 14;48(10):3231-3236. doi: 10.1039/c9dt00204a. Epub 2019 Feb 5.

Authors

Ryo Saiki¹, Haruka Miyamoto, Hajime Sagayama, Reiji Kumai, Graham N Newton, Takuya Shiga, Hiroki Oshio

Affiliation

¹ Graduate School of Pure and Applied Sciences, University of Tsukuba, Tennodai 1-1-1, Tsukuba, Ibaraki 305-8571, Japan. shiga@chem.tsukuba.ac.jp oshio@chem.tsukuba.ac.jp.

PMID: 30720038
DOI: 10.1039/c9dt00204a

Abstract

Three mononuclear iron(ii) complexes of the formula [Fe^II(H₂L^1-3)₂](BF₄)₂·x(solv.) (H₂L^1-3 = 2-[5-(R-phenyl)-1H-pyrazole-3-yl] 6-benzimidazole pyridine; H₂L¹: R = 4-methylphenyl, H₂L², R = 2,4,6-trimethylphenyl, H₂L³, R = 2,3,4,5,6-pentamethylphenyl) (1, H₂L¹; 2, H₂L²; 3, H₂L³) with asymmetric tridentate ligands (H₂L^1-3) were synthesized and their structures and magnetic behaviour investigated. Significant structural distortions of the dihedral angles between phenyl and pyrazole groups were observed and found to depend on the nature of the substituent groups. Cryomagnetic studies reveal that 1 and 2 show gradual spin crossover behavior, while 3 remains in the high spin state between 1.8 and 300 K.