Electron-spin dynamics and structures in halogen-bridged 1-D metal complexes studied by solid NMR

Magnetic properties characteristic in I-D systems were investigated in halogen-bridged mixed-valence and averaged-valence metal complexes by applying magnetic resonance techniques. Neutral-solitons and polarons formed from impurity amounts of paramagnetic Pt3+ and Pd3+ sites in I-D chains were sensitively detected by the NMR relaxation measurement. Their rapid I-D diffusion comparable to that in trans-polyacetylene was revealed in [M-II(en)(2)][(MBr2)-Br-VI(en)(2)](ClO4)(4) (M: Pt, Pd). From C-13 NMR spectra and H-1 NMR relaxation studies, [(NiX)-X-III(chxn)(2)]X-2 (X: Cl, Br) was shown to be in an averaged-valence state forming S = 1/2 I-D Heisenberg antiferromagnetic chains. [NiBr(chxn)(2)]Br-2 revealed to have the largest exchange interaction so far reported, was expected to transform into a new state at low-temperatures below 100 K. From studies on thermal motions and phase transitions associated with the I-D chain-structure in [Pt(en)(2)][PtX2(en)(2)](ClO4)(4) (X: Cl, Br), the presence of the dynamic disorder of the Pt(en)(2) chelate-ring conformation in a highly asymmetric double-well potential undetected by the X-ray diffraction was detected by the NMR relaxation measurement.