title: Synthesis, structure, and spin crossover above room temperature of a mononuclear and related dinuclear double helicate iron(ii) complexes.
abstract: A mononuclear iron(ii) complex, [FeII(L1Me)2](PF6)2(1), and a related dinuclear one, [Fe(L2C2)2](PF6)4·5H2O·MeCN (2), were prepared, where L1Meis a tridentate N3coordinating Schiff-base ligand, 1-methyl-1,2,3-triazol-4-yl-methylideneamino-2-ethylpyridine, and L2C2is 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 L1Meligands, 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 CHN 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.
authors: Department of Chemistry, Faculty of Education, Gifu University, Yanagido 1-1, Gifu 501-1193, Japan. hagiwara@gifu-u.ac.jp.
authors: Hiroaki
authors: http://orcid.org/0000-0003-0396-7965
authors: H
authors: Hagiwara
authors: Department of Chemistry, Faculty of Education, Gifu University, Yanagido 1-1, Gifu 501-1193, Japan. hagiwara@gifu-u.ac.jp.
authors: Tomoko
authors: T
authors: Tanaka
authors: Graduate School of Education, Gifu University, Yanagido 1-1, Gifu 501-1193, Japan.
authors: Shiori
authors: S
authors: Hora