Synthesis And Properties Of Carboxyl Coumarin-substituted Phthalocyaninato Zinc(Ⅱ)

Phthalocyanine and their deriativers have outstanding electronic and optical properties, along with two strong absorption at the range of 300~400 nm and 600~700 nm region. Althought the chromophore and auxochrome introduced to the phthalocyanine core will boarder and red-shifted the absorption spectrum, the effective absorption is also lack betweem 400 nm and 600 nm under the sun radiation. It is necessary to design and synthesis the phthalocyanine dyes with spectral absorption cover the visible region for dye-sensitized solar cells.Coumarin dyes have intensely absorption around 450 nm, which could complementary the light absorption scope of phthalocyanine compounds. Thus, coumarin used as a modifying group attached to the phthalocyanine core, by changing the bridging structure between coumarin ring and phthalocyanine core, exploring the relationship between bridged linkage and the spectral absorption of coumarin-substituted phthalocyanine, finally the optoelectronic properties of DSSCs based on the synthesis dyes were tested.The coumarin skeleton was synthesized according to Pechmann and Knoevenagel reaction, then coumarin intermediate reacted with 4-nitrophthalonitrile or 4-aminophthalonitrile through aromatic nucleophilic substitution, diazonium electrophilic substitution and Schiff”s condensation reaction to prepare the coumarin-substituted phthalonitriles: 4-methyl-7-(3,4-dicyanophenoxy)coumarin; 7-(3,4-dicyanophenoxy) coumarin-3-acid, 6-(3,4-dicyanophenylazo)coumarin-3-carboxylic acid, 7-hydroxy-8-(3,4- cyanophenylimino) coumarin-3-carboxylic acid. The coumarin-substituted phthalonitriles reaction with zinc iron in the catalyst of 1,8-Diazabicyclo[5.4.0]undec-7-ene(DBU) afforded four coumarin-substituted phthalocyanines: 2(3),9(10),16(17),23(24)-tetrakis-(3-carboxycoumarin-7-oxy)phthalocyaninato zinc(II), 2(3),9(10),16(17),23(34)-tetrakis-(3-carboxycoumarin-7-azo)phthalocyaninato zinc(II), 2(3), 9(10),16(17),23(24)-tetrakis-(3-carboxycoumarin-7-imino)phthalocyaninato zinc(II) and 2(3),9(10),16(17’)-tris-(4-methylcoumarin-7-oxy)-23(24)-(3-carboxycoumarin-7-azo)phthalo cyaninato zinc(II). The structure of target compounds were confirmed by IR, Uv-Visible absorption spectroscopy, elemental analysis and proton nuclear magnetic resonance.The spectral absorption properties, aggregation behavior and electrochemistry of four phthalocyanine compounds were researched in DMF solution. The coumarin-substituted phthalocyanine which connect coumarin and phthalocyanine ring through azo and imino double bands have bigger red-shifted than oxygen linkage, and the absorption have more 50 nm red-shifted than unsubstituted phthalocyanine phthalocyaninato zinc(II). In this experiment, the azo structure connected the coumarin and phthalocyanine appear a new absorption peak at 500~600 nm, supplementing the absorption of metal phthalocyanine compound in the region of light. Within the range of concentrations tested, only CAPc occurr aggregation. Combined the initial oxidation potential calculated from cyclic voltammetry with photochemical band gap of four complexs, the EHOMO and ELUMO were investigated. The ELUMO of COPC, CAPc, CSPc and OAPc is higher than the levels of TiO2 conduction band, and the ELUMO could also ensure the oxidation state of dye obtained electronic from the electrolyte. The thermogravimetric analysis showed that all synthesized carboxylic coumarin-substituted phthalocyaninato zinc were stabilized up to 200 oC.The DSSCs based on four carboxylic coumarin-substituted phthalocyaninato zinc were constructed to evaluate the photovoltaic performance of four dyes, the compound OAPc which have the asymmetric structure obtained the highest photoelectric conversion efficiency.