Geometry and orientation of molecules in a graphite fluoride matrix

Polarization dependences of the EXAFS and XANES spectra of graphite fluoride intercalation compounds C₂F_x·yA (x ≈ 1, A=Br₂, Fe(AA)₃, FeCl₃, SnCl₄; AA=acetylacetonate) synthesized by diffusion from solution were measured. The measurements were carried out in the FeK-, BrK-, and SnK-edge of absorption spectral regions using synchrotron radiation of the VEPP-3 storage ring (Institute of Nuclear Physics, Siberian Branch, Russian Academy of Sciences). The polarization dependences of effective coordination numbers and edge σ-resonance intensity are analyzed, and parameters of the local surroundings of atoms (coordination numbers, interatomic distances, Debye-Waller factors σ²) are determined. For the Br₂ intercalates, the orientation angle with respect to the matrix layers is 64±1.5°, and the interatomic distances are close to those in the gas phase. The FeCl₃ molecule forms dimers in the matrix as it does in the gas phase, and the iron atoms have tetrahedral surroundings. For the Fe(AA)₃ molecules intercalated into the matrix, the iron atoms have significantly distorted octahedral environments. For the SnCl₄ intercalates, the lowering of temperature does not cause additional coordination of Sn atoms, and structural disorder of SnCl₄ makes the major contribution to σ². Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 37, No. 6, pp. 1081–1088, November–December, 1996 Translated by L. Smolina