Synthesis And Properties Of Phenanthroimidazole Derivatives-Porphyrin

Porphyrins has a strong absorption in the spectral range of 400⁴50 nm and 500⁷00 nm,and its absorption range is wide.However,there is a narrow absorption between 450 nm and 500 nm,and the fluorescence intensity is weak.When the chromophore introduced into the ? or meso position of the porphyrin ring,the absorption range and fluorescence intensity has improved,correspondingly,the absorption of light and light quantum yield was improved,it is a view to the application of dye-sensitized solar cells.Phenanthroimidazole are a class of strong fluorescent compounds with fluorescence spectral range of 350⁶00 nm,which is a good match to the absorption spectrum range of porphyrins.In this paper,the phenanthroimidazoles were introduced into the porphyrin through the schiff base structure,the phoelectric properties of the symmetrical phenanthroimidazole-porphyrins,asymmetric phenanthroimidazole-porphyrins and Phenanthroimidazole-binuclear porphyrin were studied.The relationship between the position of bridge and the photoelectric properties of porphyrin was explored.By Weidenhagen principle,the imidazole structure was constructed to obtain four phenanthroimidazole derivatives,namely,2-?4-formylphenyl?-1H-phenanthro-[9,10-d ]imidazole?Precursor 1?,1-?4-formylphenyl?-2-?4-carboxyphenyl?-1Hphenanthro[9,10-d]imidazole?Precursor 2?,1-?4-formylphenyl?-2-?4-carboxyphenyl?-1Hphenanthro[9,10-d]imidazole?Precursor 3?,and 1,2-di?4-formylphenyl?-1Hphenanthro[9,10-d ]imidazole?Precursor 4?.The porphyrin rings with nitro groups were synthesized by the conventional Adler-longo synthesis method,Nitro is reduced,and were through dehydration condensation with phenanthroimidazole derivatives to synthesize the porphyrin P1,P2,P3,P4,P5 and P6.The structures of intermediates and compounds were characterized by IR,elemental analysis and proton nuclear magnetic resonance spectroscopy.The precursors and the target compounds were dissolved in DMF solution,respectively.The spectral absorption properties,fluorescence properties,and electrochemical properties of the symmetrical phenanthroimidazole-porphyrins,asymmetric phenanthroimidazole-porphyrins and phenanthroimidazole-binuclear porphyrin were discussed,respecitively.Substituted at the C2 position of phenylphenidimidazole of porphyrins,relative to the N1 position,the degree of enhancement of the red-shifted absorption spectra and fluorescence intensity is relatively large extent.Among them,relative to tetraphenyl porphyrin,the absorption spectra of symmetrical phenanthroimidazole-porphyrin P3 shifted 12 nm,and the degree of enhancement of the fluorescence intensity was nearly 2 times;the asymmetric phenanthroimidazole-porphyrin P5 red shifted to 13 nm,and the porphyrin unit fluorescence intensity was enhanced by nearly 3 times;the fluorescence intensity of phenanthroimidazole-binuclear porphyrin P6 is 2 times as high as mononuclear porphyrin P.Aggregation test showed that the porphyrins,which one-substituted for phenanthroimidazole P1,are easily aggregated in solution,but the absorbance of the porphyrins which bis-substituted for phenanthroimidazole,namely: the symmetrical phenanthroimidazole-porphyrins P2 and P3,asymmetric phenanthroimidazole-porphyrins P4 and P5,and phenanthroimidazole-binuclear porphyrin P6 in DMF solution changes linearly with the concentration,and are less likely to be aggregated.The test of cyclic voltammetry showed that the initial oxidation potential of the symmetrical phenanthroimidazole-porphyrins P1,P2 and P3,was 0.88,0.738,and 0.673 V,repectively,the E_HOMO was-5.28 e V,-5.138 eV and-5.073 eV,the ELUMO was-3.459 eV,-3.36 eV and-3.466 eV,repectively;Substituted at the C2 position of phenylphenidimidazole of porphyrins P3 had lower oxidation potential,the poor level of the HOMO level and LUMO level and electrons were more easily excited;the initial oxidation potential of the asymmetric phenanthroimidazole-porphyrins P4 and P5,was 0.938 V and 0.579 V,repectively,the E_HOMO was-5.338 eV and-4.979 eV,respectively,the ELUMO was-2.785 eV and-2.802 eV,repectively;Substituted at the C2 position of phenylphenidimidazole of porphyrins P5 had lower oxidation potential,the poor level of the HOMO level and LUMO level and electrons were more easily excited;the oxidation potential of phenanthroimidazole-binuclear porphyrin P6 and mononuclear porphyrin P was 0.675 V and 0.713 V,the E_HOMO was-4.660 eV and-4.760 eV,repectively,the ELUMO was-3.374 eV and-3.357 eV,repectively,phenanthroimidazole-binuclear porphyrin P6 had lower oxidation potential,the poor level of the HOMO level and LUMO level and electrons were more easily excited.The E_HOMO and ELUMO values of 6 phenanthroimidazole-porphyrin were matched with the band energy of TiO2 conduction and the vacuum level of I-/I3-respectively,and they could be used as photosensitizer for dye-sensitized solar cells?DSSCs?.