Design,Synthesis And Properties Of Chiral Amide-Bonded Porphyrins

There are several naturally existing chiral molecules with diverse and valuable characteristics.For example,sugars,peptides,etc.are all chiral compounds,and they are all found in the form of enantiomers.Although these isomers have the same physical properties,there are huge differences in their biological activity and chemical reactivity.Porphyrins,owing to their special biological significance and applications in artificial photosynthesis,nonlinear optical devices,and sensors,have triggered extensive research on their optimized synthesis and applications.Studies have shown that porphyrin derivatives have broad application prospects in the field of renewable energy,such as hydrogen evolution reaction(HER),carbon dioxide reduction reaction(CO₂RR),oxygen reduction reaction(ORR),and are also proven to be useful materials in dye-sensitized solar cells(DSSC).At the same time,porphyrins and their metal complexes can be widely studied in the biological field,such as photodynamic therapy(PDT)treatment of cancer,magnetic resonance imaging(MRI),biomedicine,drug delivery,iron chelatase in the bone marrow and Its clinical applications,and bioimaging applications.However,chemists are not limited to the porphyrin structure itself.In recent years,porphyrin derivatives with ?-?,meso-meso,and ?-meso linkages,due to their novel molecular structure and low HOMO-LUMO energy,received much attention of several researchers.Among them,chiral porphyrin derivatives with covalent linkage are the hotspots and more difficult to produce.In this research,the synthesis is mainly to introduce chiral centers into porphyrins,either through asymmetric synthesis methods or through conjugated or non-conjugated methods.This research intends to construct chiral porphyrin derivatives by introducing different amino acids into the porphyrin structure,combining the chiral characteristics of amino acid derivatives and the photophysical characteristics of porphyrin derivatives to synthesize a series of novel molecular structures for chiral porphyrin derivatives and their metal complexes.The molecular structure and electronic structure of the compound were analyzed in detail through spectroscopy,electrochemistry,and other means,and the properties of the compound were further studied by employing theoretical calculations.Based on this theme,we have planned to research environmental functional materials comprised of chiral porphyrins,with the following aspects:1.Using dicarboxylic acids with different heterocyclic structures as key precursors,eight porphyrin dimers with different functional bridging chiral amide bonds were synthesized and characterized,the spectroscopic characterizations of the above porphyrin dimers were performed.The study of chemical and electrochemical properties,combined with TD-DFT theoretical calculations,conducts in-depth discussions on the electronic structure of compounds.Studies have shown that through the adjustment of bridging groups,the spatial coupling distance between the chromophores introduced on the porphyrin can be effectively changed,and the chiral characteristics of the porphyrin can be fine-tuned.This chapter elaborates on the effective combination of molecular rational design,chiral porphyrin construction,their electronic structure,and provides useful ideas for the design and preparation of chiral porphyrin derivatives in the future.2.One-pot synthesis of zinc chiral-porphyrin compounds(Zn₂Por-PDI)and subsequently their corresponding free base porphyrins(H₄Por-PDI),linked by perylene unit has been carried out.Spectroscopic studies have recognized that due to the introduction of perylene,the newly synthesized porphyrin compound produces a new strong absorption peak at 500 nm,consequently,the new dimers have strong absorption in a longer spectral range.The introduction of chiral amide bonds makes porphyrin dimers show outstanding circular dichroism(CD),which provides a useful idea for the synthesis and properties of extended absorption chiral porphyrin derivatives.3.Through chiral amide bonding,the introduction of methyl-red makes chiral porphyrin molecules have distinctive chiral properties and produce cis-trans isomerism on ultraviolet irradiation.In this chapter,three chiral porphyrin compounds containing methyl-red were successfully synthesized,which were respectively connected to the porphyrin compound through one,two,and three amide bonds,and received an extension of the ultravioletvisible absorption and circular dichroism properties.In addition,due to the trans and cisisomerism of the-N=N-bond of the methyl-red chromophore,it can modulate its chiral properties under the irradiation of ultraviolet light.4.Increasingly serious environmental problems and complications caused by improper pH have attracted widespread attention from all aspects of life,as the cells undergo serious destructive mutations upon p H changes.In this chapter,four examples of chiral porphyrin derivatives with 8-hydroxyquinoline substitution and possessing chiral amide bonds were synthesized,and the electronic structure of the compounds was characterized by spectroscopy and electrochemical methods.Studies have shown that this series of compounds have the characteristics of "OFF-ON-OFF" type p H sensing,which provides an important reference for the design and construction of chiral porphyrin derivatives with the environmental response.