Comparison of the first solvation shell complexes show that Yb-complexes have greater 𝐵𝐵𝐵𝐵 𝑃𝑃𝑃𝑃 6 - than those for the Nd-complexes, which suggests the greater preference of PF6 -anions for Yb(III) cation than that of Nd(III) cation. The predicted bond distances show that the Nd-F distances are longer than Yb-F bonds justifying the lower interaction between Nd(III) and PF6 -compared to Yb(III) and PF6 -. Moreover, between the two RE cations under study, Yb(III) is relatively harder than Nd(III). With the F atoms of PF6 -also being hard centers, they interact better with Yb(III) compared to Nd(III) according to hard-softacid-base (HSAB) theory , which also explains the observed 𝐵𝐵𝐵𝐵 𝑃𝑃𝑃𝑃 6 - trend. Another noticeable observation is that for both RE cations, among the similar CN conformers of a particular PF6 -coordinated complex, the conformer where tridentate PF6 -coordination is present has lower 𝐵𝐵𝐵𝐵 𝑃𝑃𝑃𝑃 6 - than the conformer with more bidentate PF6 -coordination. As for example, for Nd-6-PF6 -complex, in Yb 69CN-1 conformer, where one tridentate coordinated PF6 -is present has lower 𝐵𝐵𝐵𝐵 𝑃𝑃𝑃𝑃 6 - than Yb 69CN-2 conformer, where the PF6 - are coordinated in bi-and monodentate fashion. This is likely due to the extra steric repulsion encountered in the tridentate situation where the fluoride anions have less options to reduce interactions with other fluorides.