Crystal structure, phase transition, and potassium ion conductivity of potassium trifluoromethanesulfonate

According to the results of temperature dependent powder diffractometry (Gu inier-Simon-technique) potassium trifluoromethanesulfonate is dimorphic. Th e phase transition occurs between -63 degreesC and 45 degreesC. The low-tem perature modification crystallizes monoclinic with a=10.300(3)Angstrom, b = 6.052(1) Angstrom, c = 14.710(4) Angstrom, beta =111.83(2)degrees (-120 de greesC) and the room-temperature modification with a=10.679(5) Angstrom, b= 5.963(2)Angstrom, c=14.624(5)Angstrom, beta =111.57(3)degrees, Z=6, P2(1). According to single crystal structure determination, potassium trifluoromet hanesulfonate consists of three different potassium-oxygen-coordination pol yhedra, linked by sulfur atoms of the trifluoromethanesulfonate groups. Thi s results in a channel structure with all lipophilic trifluoromethane group s pointing into these channels. By means of DSC, the transition temperature and enthalpy have been determined to be -33 degreesC and 0.93 +/-0.03 kJ/m ol, respectively. The enthalpy of melting (237 degreesC) for potassium trif luoromethanesulfonate is 13.59kJ/mol, the potassium ionic conductivity is 3 .68.10(-6) Scm(-1) at 205 degreesC.