Inclusion compounds formed by triphenylmethanol: Structure, guest dynamics and thermal stability

The crystal structure of an inclusion compound formed by triphenylmethanol with di-methylformamide was determined (space group P1 with a = 898.8(3) pm, b = 1022.3 pm, c = 1177.3pm, alpha =104.57(1)degrees, beta = 110.32(1)degrees, gamma = 96.76(1)degrees, Z = 2 at T = 300 K). The structure of compounds formed with acetone and dimethylsulfoxide were rerefined. A new assignment for the acetone compound in space group P2(1)/n allowed a better ordered description of the molecule. The structure of the dimethylsulfoxide compound at 100 K did not indicate a phase transition and reproduced basically the room temperature structure. The results were compared with the known structures of clathrates formed by triphenylmethanol with methanol and 1,4-dioxane. All triphenylmethanol inclusion compounds are unstable, and therefore their decomposition during heating was analysed by both thermalanalysis and X-ray powder diffraction. Vapor pressure measurements of the inclusion compounds were performed from 283 to 376 K. For the pure host no marked vapor pressure was detected in this temperature range with the setup used. From the logarithmic plots of vapor pressures versus temperature the heats of vaporization were determined. The dynamics of the deuterated guest molecules were studied by measurement of the temperature dependence of the H-2 NMR signals derived from powder spectra in the range 120-335 K.