Synthesis, Properties And Function Studies On Unsymmetrical Porphyrins And Their Compounds

The porphyrins are a class of macrocyclic compounds which contains four pyrrole rings linked via methine bridges. When two protons of the pyrrole nitrogen atoms are replaced by metals, they form metallophyrins. In nature, porphyrins and metalloporphyrins play an important role in biological activities as for instance hemoproteins, chlorophylls and vitamin B12. As the particular structure and the nature of the porphyrins, they are importance in the field of photo-electronic conversion, biomimetic, catalytic materials,gas sensor, solar storage, microanalysis, etc. Today, the research of porphyrin derivation are active more and more.Considerable efforts have been made to synthesize different porphyrins by modifying them on the porphine. But most of them were symmetrical. Asymmetric synthesis is the popular and forward position in the study of the organic chemistry today. Asymmetric porphyrins have popular applications in material chemistry, biomimetic chemistry, molecular recognition and catalysis.Porphyrin's periphery has 12 active positions, which could link up different structures soft side chains. So, we would synthesize new type compound of liquid crystal porphyrin with special properties by molecular design. Liquid crystal porphyrin may be used as semicond- uctor or photoconductor materials, scientists gave paid close attention to its photoeletronic property. In this paper, we synthesized three series and twenty-five new unsymmetrical porphyrins and their transitional metal and lanthanide complexes. These compounds have been characterized by elemental analyses, Uv-vis, IR spectra, 1H NMR, and MS. We also studied their luminescent properties by excitation and emission spectra and proved that porphyrin can be used as efficient sensitizer. Their thermal stabilities were also studied by differential thermal analyses. The liquid crystal properties of porphyrin have been researched by DSC and polarized microscopic observation. These studies will provide wider ground for choice and application of the materials. Our work includes the following aspects:I. Syntheses of the complexes:In this paper synthesis method of the ligands, rare earth porphyrins, and transitional metal complexes are introduced, twenty-five new compounds are divided three series.Structures of the ligands are follows:(1) meso-5-(p-octanoyloxyphenyl)-10,15,20-triphenylporphyrin(2) meso-5-(p-palmitoyloxyphenyl)-10,15,20-triphenylporphyrin(3) meso-5-(p-stearoyloxyphenyl)-10,15,20-triphenylporphyrin Structures of compounds are follows:(1) meso-5-(p-octanoyloxyphenyl)-10,15,20-triphenylporphyrin-transition-metal complexes OPTPPM(2) meso-5-(p-palmitoyloxyphenyl)-10,15,20-triphenylporphyrin-transition- metal complexes PPTPPM(3) meso-5-(p-stearoyloxyphenyl)-10,15,20-triphenylporphyrinâ‘ . transition- metal complexes SPTPPMâ‘¡. hydroxy- Rare Earth Complexes LnSPTPP(OH)II. Characterization of complexesThese complexes have been characterized by Elemental analyses, Uv-vis, IR spectra, ¹HNMR, Raman spectra, cyclic voltammetry and MS. Differential thermal analysis showed that they all have higher stability and can be stored for many years as labelled molecules for biology.â…¢.Luminescence spectroscopyTheir luminescent properties were studied by excitation and emission spectra, Quantum yields of Q band (theΦf of the S₁→S₀) fluorescence of the porphyrins are fluorescence of lanthanide complexes are all below 0.21. They have potential application as luminescence materials.The fluorescence intensities of other porphyrin complexes are much weaker than that of the porphyrin ligands and Zn porphyrin complexes. The result is same with the reference and confirmed that the transitional metal on centre of pophyrin ring quench the fluorescence of porphyrinâ…£. Liquid CrystalsThe liquid crystal properties were investigated by DSC and POM and the results show that only the porphyrin ligands with long side chains show liquid crystalline behavior, and they exhibit a high phase transition temperature and a broad mesophase temperature span. While the other porphyrin ligands and all the metal porphyrin complexes are not liquid crystalsâ…¤.Electrochemical propertiesThe spectrum shapes of Ni, Cu, Zn porphyrin complexes are similar to the porphyrin ligands, which show the redox of the porphyrin ring. The cyclic voltammograms of Mn porphyrin complexes are different from the ligands and other transition metal complexes, which showed not only the redox of the porphyrin ring, but also the redox of the metal ion. The complexes are easier to reduce than the free-base porphyrin.â…¥.Thermal studiesPorphyrin ligands and Mn complexes are stable up to nearly 200 oC, and the decomposition of the compounds is a continuous process. They were decomposed completely in the range of 200-600℃, involved the loss of side chains and the collapse of the whole porphyrin framework.