Calorimetric Study of Bis(η6-Diphenyl)chromium Fulleride [(η6-Ph2)2Cr]$$^{{ \bullet + }}$$[C70]$$^{{ \bullet - }}$$

Abstract

The molar heat capacity of the crystalline bis(η6-diphenyl)chromium fulleride [(η6-Ph2)2Cr] $$^{{ \bullet + }}$$ [C70] $$^{{ \bullet - }}$$ was determined by precise adiabatic calorimetry over the temperature range T = (6–350) K for the first time. The reversible glass-like transformation was detected on the heat capacity curve of [(η6-Ph2)2Cr] $$^{{ \bullet + }}$$ [C70] $$^{{ \bullet - }}$$ in the interval of T = (12–30) K, and its thermodynamic characteristics were estimated and analyzed. The fundamental thermodynamic functions, namely the enthalpy [H°(T) − H°(0)], the entropy [S°(T)−S°(0)], and the potential Φ° were calculated for the range from T → 0 to 350 K based on the experimentally determined molar heat capacity of [(η6-Ph2)2Cr] $$^{{ \bullet + }}$$ [C70] $$^{{ \bullet - }}$$ . The standard entropy of formation ΔfS° of the investigated fulleride was evaluated at T = 298.15 K. The standard thermodynamic characteristics of [(η6-Ph2)2Cr] $$^{{ \bullet + }}$$ [C70] $$^{{ \bullet - }}$$ were compared with the previously reported data for the studied bis(η6-diphenyl)chromium fulleride [(η6‑Ph2)2Cr] $$^{{ \bullet + }}$$ [C60] $$^{{ \bullet - }}$$ .