RESUMEN
An electrochemical sensor based on porous aromatic cages was reported, which can achieve chiral sensing of DOPA enantiomers. The prepared sensor can achieve a recognition efficiency of up to 2.6 for DOPA enantiomers. The enhanced recognition efficiency could be attributed to the cooperation of intermolecular interactions, and the efficient charge transfer process.
RESUMEN
Chiral induction has been an important topic in chemistry, not only for its relevance in understanding the mysterious phenomenon of spontaneous symmetry breaking in nature but also due to its critical implications in medicine and the chiral industry. The induced chirality of fullerenes by host-guest interactions has been rarely reported, mainly attributed to their chiral resistance from high symmetry and challenges in their accessibility. Herein, we report two new pairs of chiral porous aromatic cages (PAC), R-PAC-2, S-PAC-2 (with Br substituents) and R-PAC-3, S-PAC-3 (with CH3 substituents) enantiomers. PAC-2, rather than PAC-3, achieves fullerene encapsulation and selective binding of C70 over C60 in fullerene carbon soot. More significantly, the occurrence of chiral induction between R-PAC-2, S-PAC-2 and fullerenes is confirmed by single-crystal X-ray diffraction and the intense CD signal within the absorption region of fullerenes. DFT calculations reveal the contribution of electrostatic effects originating from face-to-face arene-fullerene interactions dominate C70 selectivity and elucidate the substituent effect on fullerene encapsulation. The disturbance from the differential interactions between fullerene and surrounding chiral cages on the intrinsic highly symmetric electronic structure of fullerene could be the primary reason accounting for the induced chirality of fullerene.
RESUMEN
The synthesis of ultra-stable chiral porous organic cages (POCs) and their controllable chiral self-sorting at the molecular and supramolecular level remains challening. Herein, we report the design and synthesis of a serial of axially chiral porous aromatic cages (PAC 1-S and 1-R) with high chemical stability. The theoretical and experimental studies on the chiral self-sorting reveal that the exclusive self-recognition on cage formation is an enthalpy-driven process while the chiral narcissistic and self-sorting on supramolecular assembly of racemic cages can be precisely regulated by π-π and C-H π interactions from different solvents. Regarding the chemical stability, the crystallinity of PAC 1 is maintained in aqueous solvents, such as boiling water, high-concentrated acid and alkali; mixtures of solvents, such as 1 M H2SO4/MeOH/H2O solution, are also tolerated. Investigations on the chiral sensing performance show that PAC 1 enables enantioselective recognition of axially chiral biaryl molecules.
