Structural Study of Electronic States in Quasi-One-Dimensional Halogen-Bridged Mixed-Metal Complexes [Ni1−xPdx(chxn)2Br]Br2

The electronic structures of quasi-one-dimensional halogen-bridged mixed-metal compounds [Ni1−xPdx(chxn)2Br]Br2 were investigated by means of powder X-ray diffraction measurements. Unit cell lengths of all directions obeyed a linear relationship when x < 0.9, whereas those deviated when x > 0.9 especially in the case of the b and c axes. This deviation can be explained by a phase change from an MIII Mott−Hubbard state to an MII−MIV charge-density-wave state because of chemical pressure caused by the substitution of Pd ions into [Pd(chxn)2Br]Br2 with smaller Ni ions.