Structural and magnetic properties of the phase transition in absorbed and non-absorbed copper(II) trans-1,4-cyclohexanedicarboxylate

A large amount of toluene can be absorbed into the 1-dimensional tunnels in copper(II) trans-1,4-cyclohexane dicarboxylate (Cu(trans-1,4-OOCC6H10C)) at room temperature, and it can be desorbed by evacuation at elevated temperatures. The reversible absorption/desorption behavior of toluene was studied by magnetic susceptibility measurements using SQUID magnetometer and by powder X-ray diffractometry with high-energy synchrotron radiation at SPring-8, Japan. The first order phase transition was observed at 160 K in the magnetic susceptibility curve for the empty (non-absorbed or desorbed) sample, and the structural difference between the low and high temperature phases was detected in the powder X-ray diffraction patterns. On the other hand, no phase transition was observed in fully toluene-absorbed sample, and the structure was similar to that of the low temperature phase of the empty sample. The absorption/desorption behavior observed in the present study coincides with the results of heat capacity measurements by adiabatic calorimetry reported previously.