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 Ni1-x

摘要

A series of single crystals of quasi-one-dimensional bromo-bridged Ni-Pd mixed-metal MX chain compounds Ni1-xPdx(chxn)(2)Br-3 (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)]Br-2 and Pd-II complex [Pd(chxn)(2)]Br-2 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 Anger 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. [References: 55]