Given hydrophobic effect and electron-deficient features, this pyridinium-based cage with two “claw”-like hydrophobic cavities can be an ideal receptor for anionic nucleotide molecules in aqueous media. Therefore, cage could utilize these “claw” cavities to capture two guests, forming the “crab” complex (
Fig. 3a). The host-guest recognition between
1·8Cl
− and G in D
2O was observed by
1H NMR titration experiments (
Fig. 3b): (1) when 0–6.0 equiv. of G was added into the solution of
1·8Cl
− in D
2O, the TPE proton signals (H
a and H
b) of
1·8Cl
− showed obvious upfield shifts (Δ
δ > 0.1 ppm) due to the shielding effect from the aromatic guanine unit of G. At the same time, H
a and H
b were split into multiple peaks, because the chiral ribose moiety of G decreases the symmetry of the cage. (2) The other proton resonances of
1·8Cl
− almost no significant shifts had occurred. This result shows that G dose not enter the central cavity but the “claw”-like cavities at two sides. (3) the proton resonances of guanine (H
1) and the ribose moiety (H
2–6) of G were obviously shifted upfield, indicating that whole G molecule is shielded by the “claw”-like cavities of
1·8Cl
−. ESI-TOF-MS provided evidence for the 1:2 stoichiometry of
1·8Cl
−⊃G
2 (
Fig. 3c). DFT theoretical simulation shows that model I is stable, in which two G are located“claw”-like cavities of
1·8Cl
− (
Fig. 3d, left). In addition,
1·8Cl
− exhibited similar recognition behavior for other nucleotides by NMR experiments (Figs. S14-S22 in Supporting information). Meanwhile, ESI-TOF-MS, UV–vis titration, and Job's plots also strongly supported the formation of these 1:2 host-guest complexes (Figs. S23-S43 in Supporting information). Due to the number of phosphate groups and the different base units,
1·8Cl
− and guests exhibit different first-step binding constants (
Ka) of ~10
2–~10
3 L/mol with the selectivity for G/GTP (Table S5 and Fig. S44 in Supporting information), indicating that the electrostatic interaction between positively-charged pyridinium units of host and negatively-charged phosphate groups of guests and hydrophobic effects from the “claw”-like cavity are main driving forces in these aqueous host-guest complexation.