Satoaki Ikeuchi

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.

Phase diagram of lithium-doped copper oxide, Cu1−xLixO ☆

Abstract Heat capacities of lithium-doped samples of CuO have been measured below room temperature by adiabatic calorimetry. The antiferromagnetic ordering transition to incommensurately modulated state was detected as a step in the heat capacity. Its concentration dependence was compatible with existing reports based on Li-NMR. The incommensurate–commensurate transition of lithium-doped copper oxide was clearly detected for the first time. The magnetic phase diagram of Cu1−xLixO was thus constructed. The suppression of both transition temperatures by the Li doping is nearly twice as strong as that expected from mean-field and percolation theories.

Calorimetric Study of MMX Chain Complexes Having Alkyl Groups, Ni2(EtCS2)4I and Ni2(n-PrCS2)4I

Heat capacities of halogen-bridged one-dimensional binuclear metal complexes (so-called MMX chain) having alkyl groups, Ni 2 (RCS 2 ) 4 I (R = Et and n -Pr), were measured by adiabatic and relaxation calorimetry. For each complex, a small broad thermal anomaly due to a spin-Peierls transition was observed around 40 K. For Ni 2 ( n -PrCS 2 ) 4 I, a first-order phase transition was observed at 205.6 K. The enthalpy and entropy of transition were estimated to be about 4.05 kJ mol -1 and 19.7 J K -1 mol -1 , respectively. The magnitude of thermal anomaly shows that the effect of molecular dynamics of ligand on the electronic state in one-dimensional chain is small for Ni complexes having localized electrons in comparison with Pt complexes.