Abstract
In continuing attempts to determine the basis for the selectivity shown by the host Ni(4-mepy)4(NCS)2 (1) toward aromatic guests, distribution data between solid and liquid phases are reported for seven ternary systems at room temperature. These consist of 1, p-xylene, and each of the following: p-bromotoluene, p-chlorotoluene, p-fluorotoluene, p-dichlorobenzene, benzene, and 4-methylpyridine, as well as the system 1-p-chlorotoluenep-dichlorobenzene. The results, as well as those for five systems already published, have been reviewed and a hierarchy of selectivity developed. After correcting the observed selectivity for inequality of guest vapour pressures the order of decreasing preference is found to be p-bromotoluene > p-dichlorobenzene > p-chlorotoluene > deuterated and protiatedp-xylenes > ethylbenzene > 4-methylpyridine > p-fluorotoluene > toluene > benzene. With the exception of 4-methylpyridine, this is the same as the order of decreasing van der Waals length of the guest molecule and, where known, the order of enthalpy of inclusion. Although longer guest molecules and those with higher vapour pressures are favoured in selectivity, guests with longer molecules are likely to have lower vapour pressures. The activity coefficients of the included guests are calculated assuming that the liquid phases follow Raoult's law.