Ni(III) Mott–Hubbard-like State Containing High-Spin Ni(II) in a Semiconductive Bromide-Bridged Ni-Chain Compound

• Published in: Inorganic chemistry 2022-06, Vol.61 (25), p.9504-9513
• Main Authors: Wakizaka, Masanori, Mian, Mohammad Rasel, Yoshida, Takefumi, Sato, Tetsu, Tanaka, Hisaaki, Miyamoto, Tatsuya, Okamoto, Hiroshi, Takaishi, Shinya, Iguchi, Hiroaki, Yamashita, Masahiro
• Format: Article
• Language: English
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/acs.inorgchem.2c00473

Halogen-bridged linear chain metal complexes (MX-Chains) are fascinating compounds that have a quasi-one-dimensional (1D) electronic system. In this study, we synthesized the first Ni-based MX-Chain compound having hydroxy groups, i.e., [Ni­(dabdOH)2Br]­Br2·[Ni­(dabdOH x )2Br]0.5·(2-PrOH)0.25·(MeOH)0.25 (1·solvent, x = ∼0.6, dabdOH = (2S,3S)-2,3-diaminobutane-1,4-diol). Single-crystal X-ray diffraction revealed that the MX-Chains in 1·solvent formed sheets and single-chain structures in the superlattice. It suggested an MH-like state, whereas the polarized reflection and Raman spectra suggested a CDW-like state. Magnetic and electron spin resonance measurements revealed that both high-spin Ni­(II) (∼15%) and low-spin Ni­(III) (∼85%) sites are present in the chain structures, i.e., the metal sites show mixed valency. Therefore, we concluded that 1·solvent adopts an intermediate state between the MH and CDW states. Moreover, a single crystal of 1·solvent exhibited semiconductive characteristics along the chain direction. This finding represents a new structural and electronic state of 1D electronic systems as well as MX-Chains.