X-ray and thermochemical studies of phase transitions in crystalline host–guest compounds of 1,1′–binaphthyl–2,2′–dicarboxylic acid with ethanol and acetone

The crystal structures of two 1:2 and 1:1 host–guest compounds between BNDA and acetone have been determined by single crystal X-ray diffraction and are comparatively discussed with reference to recently reported BNDA/ethanol clathrates of different composition. Simultaneous thermogravimetry and differential scanning calorimetry (TG–DSC) in combination with the X-ray powder diffraction (XRD) method reveal that the thermal degradation of the BNDA/ethanol 1:2 α–form clathrate takes place in two steps with the intermediate formation of the 2:1 β–form clathrate. On the other hand, desolvation of the BNDA/acetone 1:2 α–form clathrate gives no indication for the formation of any intermediate phase in the TG–DSC traces unlike the XRD studies showing the existence of the β–form during desolvation. A possible explanation of this latter property is the very similar thermal decomposition temperature of both phases. The TG–DSC results for the isothermal inclusion of vaporous ethanol and acetone indicate that this process takes place in a single step with the formation of the 1:2 BNDA/ethanol and 1:1 BNDA/acetone clathrates, respectively.