Thermodynamics of the Bis(η6-t-butylphenyl)chromium Fulleride [Cr{η6-(t-BuPh)}2]•+C60•−

Abstract

Abstract In this work, the temperature dependence of heat capacity $C_{\text{p,m}}^{o}$ = f(T) of crystalline bis(η6-t-butylphenyl)chromium fulleride between T = 6 and 360 K was measured for the first time by precision adiabatic vacuum calorimetry. Also, for the first time, the temperature dependence of EPR signal parameters of bis(η6-t-butylphenyl)chromium fulleride in the range from 118 to 298 K was investigated by electron paramagnetic resonance. In the interval 170–210 K the reversible endothermic transformation was detected and its thermodynamic characteristics were estimated. This transformation was caused by dedimerization of fullerene fragments during heating. Based on the experimental data, the standard (p° = 0.1 MPa) thermodynamic functions, namely, the heat capacity, enthalpy, entropy, and Gibbs function of heating were calculated for dimeric fulleride in the interval from T → 0 to 170 K as well as for monomeric [Cr{η6-(t-BuPh)}2]•+C60•− complex between 210 and 360 K. The standard thermodynamic properties of tested fulleride and previously studied C60 fullerite and neutral dimer (C60)2 were compared.