Fig. 8. Electrostatic potential maps for (a) AzaEx2Cage6+ and (b) BH4EN⊂AzaEx2Cage6+ obtained by using DFT calculations. Light-yellow and deep-blue colors in the maps represent negative and positive electrostatic potentials, respectively, demonstrating that the BIPY2+ units represent better π-electron acceptors on account of their stronger π-electron deficiency. DFT-optimized structures of (c) (PCA)2⊂AzaEx2Cage6+ and (d) (pyrene)2⊂AzaEx2Cage6+. The free energy changes (ΔG) for the formation of (PCA)2⊂AzaEx2Cage6+ and (pyrene)2⊂AzaEx2Cage6+ complexes are calculated to be –7.5 and –3.9 kcal mol–1, respectively.
