Synthesis Of Molecular Recognition Functional Pyrrole Macrocycles And Organic Cages

Molecular recognition plays important roles in nature and physiology.Two types of host molecules,namely the doubly N-confused phlorin and amide cages,were designed and constructed as macrocyclic and three-dimensional hosts for molecular recognition.On one hand,the prominent structural feature of the doubly N-confused phlorin is the outward-pointing NH groups on the inverted(?,?'-linked)pyrrolic unit,which is better positioned to interact with the external environment.Thus we envisioned that it would be particularly sensitive to its chemical environment.On the other hand,the three-dimensional organic cages based on amide bonds have the advantages of shape-persistency,more molecular recognition sites(such as amide groups),and can interact with the guest from different spatial perspectives.The work of this thesis consists of four parts:In the first part,the advances in molecular recognition,especially porphyrin derivatives and organic cages,were summarized.The reported porphyrin derivatives can recognize not only molecules such as nucleic acids,amino acids and sugars,but also Cu²⁺,Hg²⁺,F^-and Cl^-ions.The organic cages can be selectively combined with Li⁺and Cs⁺,can also adsorb molecules such as I₂ and Os O₄,and can even be precisely matched with rare gases to separate krypton,xenon,and radon with a concentration of only a few parts per million in the air.In the second part,a novel doubly N-confused phlorin(compound 2-1b)was synthesized successfully.Compound 2-1b was obtained by Fouck-Acylation,Vilsmeier and[2+2]acid-catalyzed condensation using pyrrole as raw material.In the process of synthesizing compound 2-1b,we also found its oxidized derivative,namely the doubly N-confused phlorinone(compound 2-9b).The compound 2-1b could be oxidized directly to 2-9b by treating with 2,3-Dichloro-5,6-dicyano-1,4-benzoquinone(DDQ).These compounds were characterized by ¹H-NMR,¹³C-NMR,LC-MS,single crystal X-ray diffraction and UV-Vis absorption spectrum.In the third part,the molecular recognition properties of the doubly N-confused phlorin(compound 2-1b)was mainly studied.Compound 2-1b showed different colors in different solvents,especially in methanol and ethanol.The UV-Vis absorption spectrum of compounds 2-1b in methanol and ethanol showed obvious red-shift,so it could differentiate methanol and ethanol.At the same time,the molecular recognition properties of the doubly N-confused Phlorinone(compound2-9b)was also discussed.Compound 2-9b has high selectivity for fluoride recognition by Nuclear magnetic titration and UV titration,and its recognition mechanism is deprotonation characterized by ¹H-NMR,¹⁹F-NMR.In the fourth part,the transformation of imine-bonded organic cage into amide-bonded organic cage was explored.So far,most of the reported organic cages are synthesized by reversible bonds(dynamic covalent bonds),which have poor chemical stability and are deconstructed in the presence of water(especially in the presence of acid or base).To improve chemical stability of the organic cage,the reported imine-bonded organic cage(compound CC3-R)was oxidized into amide-bonded organic cage with sodium chlorite.The results showed that the obtained product might contain amide bond.The structure of the compound is not confirmed,and the related research is still in progress.