Chiral Recognition Of Monoalcohols By Benzene Tricarboxamide-Linked Trisporphyrinates

In recent years, porphyrins have been widespreadly concerned in the field of supramolecular chemistry. Porphyrins have been often used in the study of chiral recognition due to their strong absorption in Soret band region. Bisporphyrins have been intensively studies in literature reports. But few trisporphyrinates have been reported, especially on the recognition of monodentate chiral ligands.In this paper, we studied the chiral recognition ability of benzene tricarboxamide-linked zinc trisporphyrinate [Zn3-1] to a number of monoalcohols. CD titration spectra showed that stoichiometry controlled the chiral induction and chiral inversion, which is due to the formation of 1:1 and 1:2 host-guest complexes with the concentration change of guest. In order to further confirm the mechanism, we designed the compounds [ZnNi2-1], [Zn2Ni-1], and measured the corresponding CD spectra with chiral monoalcohols, the CD titration spectra were corresponding to the first and second steps of [Zn3-1]. It shows that the chiral recognition progress is divided into two steps. We have also further investigated the chiral recognition mechanism by the single crystal structure of the host-guest complex, equilibrium constants, DFT calculations and NMR titration. These results reveal that the host-guest complex adopts to the “inside” binding mode, and the hydrogen bonds are formed between the carbonyl oxygens of the porphyrin and the hydroxyl group of monoalcohols. For aromatic alcohols, there are also ?-? interactions involved. These interactions further stabilize the host-guest complex.