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Synthesis and Spectroscopic Properties of Porphyrin-C60 Dyad Bearing a Carboxylic Acid Group With Potential Use in Solar Cells
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1  Departamento de Química, Universidad Nacional de Río Cuarto, Agencia Postal Nro 3, X5804BYA Río Cuarto, Argentina

Abstract: Novel porphyrin-C60 dyad (H2P-C60) was synthesized by 1,3-dipolar cycloaddition using 5-(4-carbonylphenyl)-10,15,20-tris(4-methoxylphenyl)porphyrin (H2P), N-methylglycine and 1,2-dihydro-1,2-methanofullerene[60]-61-carboxylic acid (acid-C60). This dyad was designed to improve the intramolecular electron transfer capacity. Thus, the electron-donor capacity of the porphyrin moiety is enhanced by methoxy group substitution on the macrocycle peripheries. The H2P moiety is attached to a highly electron-withdrawing C60 structure. Also, the C60 bears a remaining carboxylic acid group, which could be able to benefit the orientation of dyad adsorbed on the semiconductor electrode, such as SnO2. Furthermore, the donor property of H2P was increased by forming complex with Zn(II) (ZnP-C60 dyad). Spectroscopic studies show only a very weak interaction between the chromophores in the grown state. The emission of the porphyrin moiety in the dyads is quenched by the attached fullerene C60 moiety. In this system, two processes may be contributing to enhance the charge injection efficiency of dyad, one involves an antenna effect that produces energy transfer from porphyrin to C60 and the other includes electron transfer from prophyrin moiety to C60. This dyad design, with C60 in direct contact with the substrate through the free carboxylic acid group, is a promising architecture of organic material for spectral sensitization of semiconductor solar cells.
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