4.17 - One-Dimensional Ni(III) and Pd(III) Mott Insulators

Abstract

Although quasi-one-dimensional halogen-bridged complexes (MX chains) have been studied extensively, most of the MX chains reported are in a charge-density-wave (CDW) state (X⋯MII⋯XMIVX⋯). The first M(III) Mott–Hubbard (MH) complex was reported in 1981, and its remarkable physical properties have been reported. More recently, our group has prepared the first Pd(III) MH complex by utilizing the following two methods: partial substitution with Ni(III) ions, [Ni1−xPdx(chxn)2Br]Br2, and chemical pressure via long alkyl chains attached to the counteranions, [Pd(en)2Br](Cn–Y)2∙4H2O. In both systems, the electronic states of the bromide-bridged Pd MX chains were established via the Pd⋯Pd distances. The results show that the CDW and MH states are stabilized when Pd⋯Pd distances are longer and shorter than 5.26Å, respectively.