Thermodynamic properties of bis-(η6-cumene)chromium fulleride [(η6-PhCH(CH3)2)2Cr].+[C60].- over the range from T → (0 to 310) K

In the present research, the temperature dependence of heat capacity C-p,m(o) = f(T) of crystalline bis-(eta(6)-cumene)chromium fulleridel [(eta(6)-PhCH(CH3)(2))(2)Cr](.+)[C-60](.-) has been measured between T = (6 and 310) K in the precision adiabatic vacuum calorimeter and reported for the first time. Also, for the first time, the temperature dependence of EPR signal parameters of bis-(eta(6)-cumene)chromium fulleride over the range from T = (120 to 290) K was investigated by electron paramagnetic resonance. In the interval from T = (196 to 240) K the reversible endothermic transformation was detected and its thermodynamic characteristics were estimated. This transformation was caused by dissociation of dimer (C-60(-))(2) and formation of fulleride [(eta(6)-PhCH(CH3)(2))(2)Cr](.+)[C-60](.-) during heating. The experimental results have been used to calculate the standard (p(o) = 0.1 MPa) thermodynamic functions C-p,m(o)/R, Delta H-T2(T1)m(o)/RT, Delta S-T2(T1)m(o)/R, and Phi(o)(m)/R = Delta S-T2(T1)m(o)/R - Delta H-T2(T1)m(o)/RT (where R is the universal gas constant) for dimeric fulleride over the range from T (0 to 196) K and for monomeric complex [(eta(6)-PhCH(CH3)(2))(2)Cr](.+)[C-60](.-) between T = (240 and 310) K. (C) 2011 Elsevier Ltd. All rights reserved.