Valence Structures and Spin Dynamics in One-Dimensional Mixed-Metal Complexes, [Cu (chxn)_2] [PtX_2 (chxn)_2]X_4 (X:CI, Br)

We measured the Raman, UV-visible and ^<13>C CP-MAS NMR spectra of halogen-bridged 1-D Cu-Pt mixed-metal complexes, [Cu (chxn)_2] [PtX_2 (chxn) 2]X_4 (X : Cl and Br), consisting of -X-Cu-X-Pt-X-chain. The Raman spectra showed an overtone progression of symmetric stretching mode of Pt (IV) -Cl atoms and the fine structures with halogen isotopic splitting in Pt-Cl band below ca. 50 K. The broad carbon signals of the ^<13>C NMR spectra observed at room temperature are attributable to strong paramagnetic effect from Cu (II) sites. This result is supported by the weak antiferromagnetic interactions between Cu (II) sites in the chain.