title: In air a spin crossover active iron(II) complex of amine/NCBH3(-) ligands is converted to a low spin complex of imine/CN(-) ligands.
abstract: Two new mononuclear Fe(II) complexes, [FeL1(NCBH3)2] (1) and [FeL2(CN)2]·3H2O (2) (L1 = N,N'-bis(2-pyridylmethyl)-1,2-ethanediamine, L2 = N-(2-pyridylmethyl)-N'-(2-pyridylmethylene)-1,2-ethanediamine) were synthesized from the same starting solution under different atmospheric conditions. Complex 1 was isolated under an N2 atmosphere with an expected molecular structure, namely a tetradentate L1 ligand and two NCBH3(-) co-ligands wrapping an iron(ii) ion. It exhibits a gradual spin crossover centered around 355 K, as confirmed by X-ray crystallography, magnetic, DSC and Mössbauer studies. Complex 2 was isolated in the presence of air. One of the secondary amine groups in L1 undergoes an in situ oxidative dehydrogenation, forming a new monoimine asymmetric ligand L2. Besides, a CN(-) co-ligand is also in situ generated from NCBH3(-) during the reaction. The strong ligand field strength imposed by CN(-) and L2 stabilizes 2 in the LS state. Solvent water molecules in complex 2 are hydrogen bonded into a well-defined 1D water chain. 2 shows a proton conductivity of 8.9 × 10(-5) S cm(-1) at 55 °C and 95% relative humidity.
authors.affiliation: School of Chemical Engineering, Nanjing University of Science and Technology, 210094 Nanjing, P. R. China.
authors.forename: Jian
authors.initials: J
authors.lastname: Zhou
authors.forename: Bo-Wen
authors.initials: BW
authors.lastname: Zhu
authors.forename: Jie
authors.initials: J
authors.lastname: Luan
authors.forename: Zhan
authors.initials: Z
authors.lastname: Liu
authors.forename: Jing-Kun
authors.initials: JK
authors.lastname: Fang
authors.forename: Xin
authors.initials: X
authors.lastname: Bao
authors.forename: Guo
authors.initials: G
authors.lastname: Peng
authors.forename: Jiri
authors.initials: J
authors.lastname: Tucek
authors.forename: Song-Song
authors.initials: SS
authors.lastname: Bao
authors.forename: Li-Min
authors.initials: LM
authors.lastname: Zheng