Tuning of charge density wave strengths by competition between electron-phonon interaction of Pd^II-Pd^IV mixed-valence states and electron correlation of Ni^III states in quasi-one-dimensional bromo-bridged Ni-Pd mixed-metal MX chain compounds Ni_1-xPd_x(chxn)₂Br₃

A series of single crystals of quasi-one-dimensional bromo-bridged Ni-Pd mixed-metal MX chain compounds Ni_1-xPd_x(chxn)₂Br₃ (chxn = 1(R),2(R)-diaminocyclohexane) have been obtained by electrochemical oxidation methods of the mixed methanol solutions of parent Ni^II complex [Ni(chxn)₂]Br₂ and Pd^II complex [Pd(chxn)₂]Br₂ with various mixing ratios. To investigate the competition between the electron correlation of the Ni^III states (or spin density wave states) and the electron-phonon interaction of the Pd^II-Pd^IV mixed-valence states (or charge density wave states) in the Ni-Pd mixed-metal compounds, IR, Raman, ESR, XP, and Auger spectra have been measured. The IR, resonance Raman, XP, and Auger spectra show that the Pd^II-Pd^IV mixed-valence states are influenced and gradually approach the Pd^III states with the increase of the Ni^III components. This means that in these compounds the electron-phonon interaction in the Pd^II-Pd^IV mixed-valence states is weakened with the strong electron correlation in the Ni^III states.