Cooperativity of dynamics of 18-crown-6 molecule forming one-dimensional chain in Cs2(18-crown-6)3[Ni(dmit)2]2.
Heat capacity of Cs2(18-crown-6)3[Ni(dmit)2]2 was measured by adiabatic calorimetry. A broad thermal anomaly was observed around 225 K. The entropy gain (about 52 J K(-1) mol(-1)) is much larger than that expected for twofold disordering of 18-crown-6 assumed in the previous structure analysis. The shape of thermal anomaly was qualitatively explained by a linear Ising model developed for cooperative disordering in polymers. The 18-crown-6 molecules forming a one-dimensional chain in the crystal are orientationally disordered with moderate cooperativity.
Ikeuchi
Satoaki
S
Research Center for Molecular Thermodynamics, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan.
Miyazaki
Yuji
Y
Takeda
Sadamu
S
Akutagawa
Tomoyuki
T
Nishihara
Sadafumi
S
Nakamura
Takayoshi
T
Saito
Kazuya
K