ABSTRACT The CDW strengths in quasi-one dimensional halogen-bridged Pt, Pd and Ni mixed-valence compounds, [MII(AA)2][MIVX2(AA)2]Y4 are tuned by substituting the constituent metal ions, bridging halogens, in-plane ligands, and counteranions. Relaxation processes from the excited states, dynamics of solitons and polarons, and third-order nonlinear optical properties depend on their CDW strengths. The SDW strengths in [NiIII(chxn)2X]Y2 are tuned by substituting bridging halogens and counteranions. These compounds are not Mott-insulators but Charge-transfer-insulators. The competition between the CDW states in PdII-PdIV sites and the SDW states in NiIII sites in the Ni-Pd mixed-metal compounds, Ni1-xPdx (chxn)2Br3 are investigated. As a result, the PdII-PdIV states are approaching to the PdIII states, because of the stronger on-site Coulomb interaction in NiIII sites.
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