Ionic liquid (IL) development efforts have focused on achieving desired properties via tuning of the IL through variation of the cations and anions. However, works geared toward a microscopic understanding of the nature and strength of the intrinsic cation-anion interactions of ILs have been rather limited such that the intrinsic strength of the cation-anion interactions in ILs is largely unknown. In previous work, we employed threshold collision-induced dissociation approaches supported and enhanced by electronic structure calculations to characterize the nature of the cation- anion interactions in and determine the bond dissociation energies (BDEs) of a series of four 2:1 clusters of 1-alkyl-3-methylimidazolium cations and tetrafluoroborate anions, [2C(n)mim:BF](+). The cation was varied over the series: 1-ethyl-3-methylimidazolium, [C(2)mim](+), 1-butyl-3-methylimidazolium, [C(4)mim](+), 1-hexy1-3-methylimidazolium, [C(6)mim](+), and 1-octyl-3-methylimidazolium, [C(8)mim](+), to determine the structural and energetic effects of the size of the 1-alkyl substituent on the binding. The variation in the strength of binding determined for these [2C(n)mim:BF4](+) clusters was found to be similar in magnitude to the average experimental uncertainty in these determinations. To definitively establish an absolute order of binding among these [2C(n)mim:BF4](+) clusters, we extend this work here to include competitive binding studies of three mixed 2:1 clusters of 1-alkyl-3-methylimidazolium cations and tetrafluoroborate anions, [C(n-2)mim:BF4:C(n)mim](+) for n = 4, 6, and 8. Importantly, the results of the present work simultaneously provide the absolute BDEs of these mixed [C(n-2)mim:BF4:C,mim](+) clusters and the absolute relative order of the intrinsic binding interactions as a function of the cation with significantly improved precision. Further, by combining the thermochemical results of the previous and present studies, the BDEs of the [2C(n)mim:BF4](+) clusters are more accurately and precisely determined.