Investigation of New Ionic Plastic Crystals inNR4BBu4 (R = Me, Et, Pr, Bu, Pen)

摘要

In order to investigate new ionic plastic crystals, differential-scanning-calorimetry (DSC), nuclear-magnetic-resonance (NMR), and electrical conductivity measurements were carried out in NR_(4)BBu_(4) (R = Me, Et, Pr, Bu, Pen) salts. DSC measurements showed a low entropy change of 29.1 J K~(-1) mol~(-1) at a melting point and large values of 35.7 and 17.8 J K~(-1) mol~(-1) at phase transitions in NEt_(4)BBu_(4) crystals. In contrast, the other compounds of NR_(4)BBu_(4) (R = Me, Pr, Bu, Pen) showed large entropy changes at each melting point. On the basis of solid-state ~(1)H and ~(13)C NMR spectra results, tumbling motions were detected in the NMe_(4)BBu_(4) and NEt_(4)BBu_(4) crystals. Isotropic reorientation motions of partial ions were observed in the NPr_(4)BBu_(4) crystals. Although NR_(4)BBu_(4) (R = Me, Et, Pr) have no plastic phases, low activation energies of ion transfer were recorded in these salts. These results suggest that the tumbling motions can perform the resemble effect as isotropic reorientation in plastic crystals.