Stabilization of Pd(III) states in nano-wire coordination complexes

摘要

In spite of a long history of quasi-one-dimensional halogen-bridged complexes (MX-chains), all Pt and Pd complexes form the charge-density wave (CDW) state (-X…M~Ⅱ…X-M~Ⅳ-X…), while all Ni complexes form Mott-Hubbard (MH) states (-X-Ni~ⅢX-N~Ⅲ-X-), without exception. We have succeeded in stabilizing the Pd(m) MH state for the first time by utilizing the following two methods: partial substitution with Ni(Ⅲ) ions, [Ni_(1-x)Pd_x(chxn)_2Br]Br_2, and chemical pressure via long alkyl chains introduced as counter-anions, [Pd(en)_2Br](C_n-Y)_2·H_2O. In both systems, it has been revealed that the electronic state of bromo-bridged Pd compounds are determined by the Pd…Pd distances, in other words, CDW and MH states are stabilized when Pd…Pd distances are longer and shorter than 5.26 A, respectively.