A high temperature reversible phase transition in a supramolecular complex of 15-crown-5 with tetraphenylboron sodium

摘要: A supramolecular crystal, [Na(15-crown-5)][BPh4] (1), (15-crown-5 = 1,4,7,10,13-pentaoxacyclopentadecane, NaBPh4 sodium tetraphenylboron), has been obtained by mixing the ethanol solution of 15-crown-5 and in molar ratio 1 : 1. The crystal structure was determined at 293 K, revealing that two [Na(15-crown-5)]+ cations form a dimer via sharing one side-edge coordination pentagonal pyramids; also, there are significant H-bonding interactions between anions supramolecularly dimeric cations. Differential scanning calorimetry (DSC) showed 1 undergoes reversible first-order phase transition ca. 391 K (Tc) upon heating, with thermal hysteresis 19 K. ΔH ΔS were estimated to be 6.9 kJ mol−1 17.7 J K−1, respectively, heating run. variable-temperature powder X-ray diffraction dielectric spectra collected, both disclosed no difference low- high-temperature phases. These results suggest is an ordered–disordered type, which probably involves change anion configuration.