Chirality Transfer In M-phthalic Diamide-linked Bisporphyrin Systems

Porphyrins are often used as the hosts to recognize a series of chiral guests,because of their unique properties.That is also a hot topic in current research.Studies on polydentate ligands such as amino acids,amino alcohols,diamines,and di-alcohols are extensive,while studies on mono-dentate ligands such as monoamines and mono-alcohols are rare.Accordingly,we have designed and synthesized four novel zinc bisporphyrinates,and inverstigated the chirality transfer by using a series of chiral monoamines and chiral mono-alcohols as guests.Our studies suggest the chirality transfer in these systems are dependent on the substituents of the linker and the guests.In the first part of this thesis,we introduced the chirality transfer in these zinc bisporphyrinate-monoamine systems.CD spectroscopy studies showed that when 1-naphthylethylamine was used as a chiral guest and zinc porphyrinates [Zn2-NABis],[Zn2-BABis] were used as hosts,sign inversion of the CD was observed during the titration.Both CD and NMR spectra suggest that 1:1 and 1:2 complexes are formed in solution and DFT calculations support the proposal that steric interactions between the substituent of the host and the second guest in the 1:2 complex leads to this inversion.In the second part of this thesis,we introduced the chirality transfer in the zinc bisporphyrinate-monoalcohol systems.The mixture of [Zn2-SALBis] and most chiral mono-alcohols can produce CD signals,but compared with those for other zinc porphyrinates,the CD signals are significantly weaker,even for some guests,such as 1-phenylpropanol and 1-phenylbutanol,no observable signals were obtained.The mixture of [Zn2-MBABis] and six chiral monoalcohols can produce CD signals.Compared with those for other zinc porphyrinates,the corresponding CD signals were more intensive.[Zn2-BABis] also can function as a chirality probe for a series of chiral mono-alcohols.When the guests are 1-phenylethanol,1-phenylpropanol and 1-phenylbutanol,the corresponding CD signals are related to the length of carbon chains of their substituent: when the substitutent of the guest changes from methyl to ethyl and propyl groups,the CD signal gradually weakened and then reversed for 1-phenylbutanol.More importantly,we obtained the single crystal structures of the zinc bisporphyrinate-monoalcohols complexes.Their crystal structures reveal that there are two type ?–? interactions: One is formed between the guest and phenyl ring of the linker;another is formed between the guest and the porphyrin plane.Both NMR and CD studies suggest the 1:1 host-guest complex is dominate in solution under our experimental condition.DFT calculations suggest that in the host-guest complexes,the nature of the ?–? interaction and steric hindrance makes a difference.For R-1-phenylethanol,?–? interactions play a leading role in chirality transfer process,which lead to positive exciton chirality.For R-1-phenylbutanol,steric repulsion plays a leading role in chirality transfer process,which lead to negative exciton chiralty.