Crystal structure determination of the silver carboxylate dimer [Ag(O_2C_(22)H_(43)]_2, silver behenate, using powder X-ray diffraction methods

摘要

High-resolution powder X-ray diffraction has been used to determine the crystal structure of silver behenate, [Ag(O_2C(CH_2)_(20)CH_3]_2. Using CASTEP density functional plane wave pseudo-potential techniques to obtain an optimized structural model, Rietveld refinement of the structure gives R_(wp) = 8.66%. The unit cell is triclinic, space group P1, with cell dimensions of a = 4.1769(2) A, b = 4.7218(2) A, c = 58.3385(1) A, α = 89.440(3)°, β = 89.634(3)°, γ = 75.854(1)°. The structure is characterized by an 8-membered ring dimer of Ag atoms and carboxyl groups with a fully extended all-trans configuration of the alkyl side chains. The dimers are joined by four-membered Ag-O rings creating a polymeric network, giving rise to one-dimensional chains along the b-axis. This structure is supported by EXAFS measurements of the local structure around the silver atoms and IR measurements.