Nickel K-edge and Bromine K-edge EXAFS spectra have been measured for Br-bridged one-dimensional NiII-NiIVmixed valence compounds and their reference NiIIand NiIIIcomplexes. Fourier transforms of the Br K- and Ni K-edge EXAFS data of the mixed valence compounds show one and two sharp peaks, respectively, assigned to the Br-Ni distance, and the Ni-N and Ni-Br distances. By applying least-squares curve-fitting analyses for the Fourier back-transformed first peaks, a mean NiIV-Br distance for the mixed valence compounds has been determined to be 2.64 A, which is comparable to 2.63 A for the discrete NiIIIcomplex. This suggests a significant elongation of the NiIV-Br bond owing to the charge transfer interaction between the NiIIand NiIVatoms, resulting in the high electrical conductivities of NiII-NiIVcompounds as compared with those of the Pd and Pt analogues. Mean Ni-N distances were accurately determined and were found to increase in the order, octahedral high-spin NiII> octahedral NiIII≃ octahedral NiIV, and square-planar NiIIin the mixed valence compound ≥ square-planar low-spin NiIIin the discrete complex. The NiII… Br distance in the mixed valence compound could not be obtained, possibly Awing to the essentially weak bonding nature.
- nickel(II, IV)
- one-dimensional compound
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Materials Chemistry