Absorption/Desorption Properties of Some Simple Molecules in Copper (II) Dicarboxylate Complexes

Large amount of toluene and carbon tetrachloride can be absorbed into 1-dimensional tunnels in copper(II) trans-1,4-cyclohexanedicarboxylate Cu2(OOC-C6H10-COO) under the saturated vapor pressure at room temperature. The absorbed toluene and carbon tetrachloride can be desorbed easily by evacuation above room temperature, and the absorption/desorption is completely reversible. The absorption/desorption phenomena were studied for the empty, partly and fully toluene and carbon tetrachloride absorbed samples by adiabatic calorimetry between 13K and 300K and by powder X-ray diffractiometry with high-energy synchrotron radiation at SPring-8 of JASRI. The first-order phase transition was observed in the empty sample. The partly toluene-absorbed samples showed smaller heat capacity anomaly at higher temperatures than the empty sample. On the other hand, the partly carbon tetrachloride-absorbed samples showed smaller heat capacity anomaly at lower temperatures than the empty sample. The difference in the two cases was discussed on the basis of structural and thermal data.