| Research Abstract |
Quasi-one-dimensional halogen-bridged mixed-valence metal compounds have attracted much attention because they show very interesting physical properties such as intense and diachronic intervalence charge transfer bandsm luminescence with large Stokes shifts, overton progression of resonance Raman spectra, large third order non-linear optical properties, solitons, polarons, etc. Among these compounds, the Pt and Pd compounds take the M (II)-M (IV) mixed valence states or CDW states, where the bridging halogens are distorted from the midpoints between neighboring two metal ions. On the other hand, the Ni compounds take the Ni(III) states or SDW states, where the bridging halogens are located at the midpoints between two metal ions. The Ni compounds have the similar electronic structures to those starting materials of copperoxide supercondutors. Then, the doping to the compounds are very interesting. According such strategy, we have synthesized Ni-Pd mixed-metal complexes by electrochemic
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al methods. In order to investigate their electronic structures, we have measured IR, Raman spectra, XPS, Auger spectra and ESR spectra.
The XPS and Auger spectra revealed that the oxidation states of the Ni ions is +3, but the Pd(II)-Pd(IV) mixed-valence states approach the Pd(III) states with increase of Ni components. In the IR spectra, the doublet of υ(N-H) in Pd(II)-Pd(IV) is gradually changing to the singlet, indicating that the Pd(II)-Pd(IV) state approach the Pd(III) states. In the Raman spectra, the intensity and the number of overtone of υ(Pd(IV)-Br) decrease with increase of the Ni components as observed in IR spectra. The integrated spin susceptibilities at room temperature are enhanced compared with those pure mixture of Pd(II)-Pd(IV) and Ni(III), indicating that the Pd(II)-Pd(IV) states are changed to the Pd(III) sates.
As mentioned above, the Pd(II)-Pd(IV) states are influenced and changed to the Pd(III) states with increase of the Ni(III) components. This is due to the stronger electron correlation of the Ni ions. Less
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