Synthesis,Spectroscopic And Electrochemical Studies Of Imine Bond-bridged Zinc Phthalocyanines Conjugated With Aromatic Substituents

The sensitizers is the important part of the dye-sensitized solar cell,phthalocyanines and their metal complexes are typical NIR dyes have been widely used in dye-sensitized solar cell as the sensitizer due to it's unique optical absorption,heat and chemical stability and facile modification of the chromophore skeleton.But the low solubility in commom solvent,easy to aggregate and narrow spectral absorption rang prevent the phthalocyanines application in dye-sensitized solar cell.Imine compounds which have carbon-nitrogen double bond??C?N??structure,and the absorption spectral is complementary with the absorption spectra of phthalocyanine.In this paper,five aromatic imide-substituted zinc phthalocyanines were designed and synthesized to expand the absorption spectra of phthalocyanines,and prevent the aggregate.The 4-aminophthalonitrile?Pn1?was obtained by reducing 4-nitrophthalonitrile using iron powder as reductant.Then 4-[?4-methylbenzylidene?amino]phthalonitrile?Pn2?;4-[?4-methoxylbenzylidene?amino]phthalonitrile?Pn3?;4-[?furan-2-methylidene?amino] phthalonitrile?Pn4?;4-[?thiophen-2-methylidene?amino]phthalonitrile?Pn5?;4-[?diphenylmethylidene?amino]phthalonitrile?Pn6?,were prepared with 4-aminophthalonitrile,4-methylbenzaldehyde,4-methoxybenzaldehyde,2-furaldehyde,2-thenaldehyde,diphenylmethanone as raw materials.Subsequently 2?3?,9?10?,16?17?,23?24?-tetra-[?4-methylbenzylidene?amino]zinc phthalocyanine?Pc1?;2?3?,9?10?,16?17?,23?24?-tetra-[?4-methoxylbenzylidene?amino]zinc phthalocyanine?Pc2?;2?3?,9?10?,16?17?,23?24?-tetra-[?furan-2-methylidene?amino]zinc phthalocyanine?Pc3?;2?3?,9?10?,16?17?,23?24?-tetra-[?thiophen-2-methylidene?amino]zinc phthalocyanine?Pc4?;2?3?,9?10?,16?17?,23?24?-tetra-[?diphenylmethylidene?amino]zinc phthalocyanine?Pc5?were obtained by self-cyclotetramerization of the imide-substituted phthalonitrile.The target compounds were characterized by FTIR,1H NMR and elemental analyses.The characterization data of the compounds was consistent with the assigned formula.The absorption properties of aromatic imide-substituted zinc phthalocyanines were investigated according to the UV-vis spectroscopy recorded in DMF solution.The results indicated that the Q-band of aromatic imide-substituted zinc phthalocyanines exhibited a red shift of 34 nm,36 nm,43 nm,45 nm,48 nm,respectively,the absorbance intensity of the B-band has been significantly enhanced,compared with that of the unsubstituted znic phthalocyanine.The aggregation behavior of aromatic imide-substituted zinc phthalocyanines were investigated according to the UV-vis spectroscopy recorded in DMF at different concentrations.The results showed that the target compounds existed in a form of monomer in DMF solution?0.002 0.010 mmol/L?.Their redox behavior was investigated by cyclic voltammetry,they have similar curves.And the HOMO and LUMO level was calculated by cyclic voltammetry curves.The ELUMO of the aromatic imide-substituted zinc phthalocyanines were-3.25 e V?-3.27 eV?-3.34 eV?-3.42 eV and-3.45 eV,the EHOMO were-4.71 eV?-4.69 eV?-4.72 eV?-4.77 eV and-4.75 eV,which matched with the conduction band of nano-TiO₂,and achieved the purpose of dye regeneration.