Chiral Recognition By Amide-Linked Achiral Bisporphyrin And Chiral Bisporphyrin

Due to their unique structures and properties,porphyrins have been widely used in most fields of contemporary scientific research.In the aspect of chiral recognition,most stuies are focused on the recognition of bidentate chiral molecules or using achiral bisporphyrins as recognition hosts.However,there are few reports on the recognition of monodentate chiral molecules or using chiral bisporphyrins as the host.In the second chapter of this thesis,one achiral biporphyrin,[Zn2(AmBis)],has been synthesized.We have intensively investigted the chirality transfer from a chiral monoamine to this zinc bisporphyrin.Our studies suggest there are two coordination equilibria when[Zn2(AmBis)]is mixed with chiral monoamines,both processes induce the same sign of CD signals.In this work,we obtained the first crystallographically characterized 1:2 complexes between a bisporphyrin and a monoamine.The structure reveal that the binding modes between the two ligands and the host are different One ligand binds to the host through coordinations,π-πinteractions,hydrogen bonds,and the other binds to the host through coordinations,π-π interactions.We recognize that hydrogen bonding is not necessary for host-guest complexes to form "sandwich" configurations.In the third chapter,one chiral biporphyrin,[Zn2(DDTABis)],has been synthesized.It can effectively chiral recognize chiral amino acid esters.Our studies suggest there are also two coordination equilibria when[Zn2(DDTABis)]is mixed amino acid esters.The aliphatic amino acid esters bind to the host through coordinations,hydrogen bonds,and the aromatic amino acid esters bind to the host through coordinations,hydrogen bonds,π-π interactions.The fitting results of UV-vis and CD spectra showed that the binding constants between[Zn2(DDTABis)]and the enantiomers of amino acid esters were different.The binding constants between[Zn2(DDTABis)]and D-amino acid esters are larger.For PheOEt,the enantioselective parameter reaches 8.35,which confirms the chiral recognition ability of this chiral bisporphyrin.