2.4.1. Acid Dissociation Constant (pKa)

The formation of the resultant supramolecules can be predicted according to the pKa difference (ΔpKa = pKa[base] − pKa[acid]) of corresponding acid/base pairs [24,25]. It is generally accepted that a salt will be formed if the ΔpKa value is greater than 3, and a ΔpKa value less than 0 will lead to the formation of cocrystals. However, if the ΔpKa value is in the range of 0~3, it will be not accurate to predict the resulting formation [25]. The pKa values of ARI and CCF were calculated by MarvinSketch 15.6.29 (ChemAxon, Budapest, Hungary) [26].
