Competition between electron-correlation in Ni^III states and electron-phonon interaction in Pd^II-Pd^IV mixed-valence states in quasi-one-dimensional halogen-bridged mixed-metal complexes, Ni_1-xPd_x(chxn)₂Br₃

A series of single crystals of quasi-one-dimensional halogen-bridged Ni-Pd mixed-metal compounds, Ni_1-xPd_x(chxn)₂Br₃ (chxn=1R,2R-cyclohexanediamine) have been obtained by electrochemical oxidation methods. In order to investigate the competition between the electron-correlation in the Ni^III states (SDW states) and the electron-phonon interaction in the Pd^IIPd^IV mixed-valence states (CDW states) in the Ni-Pd mixed-metal compounds, the single-crystal electrical conductivities, IR, resonance Raman spectra, ESR, magnetic susceptibilities, and XPS, have been measured. The electrical conductivities of these compounds show semiconducting behavior with the conductivities maximized and the activation energies minimized at x=ca. 0.5. The IR, resonance Raman spectra, and XPS show that the pd^II-pd^IV mixed-valence states are influenced and approaching to the Pd^III states with the increase of the Ni^III components.