Hybrids of Thio-ethylporphyrazine with Nanocarbons for Photoinduced Electron Transfer

International Conference on Hybrid and Organic Photovoltaics
Proceedings of International Conference on Hybrid and Organic Photovoltaics 2015 (HOPV15)

Poster, Sandra Belviso, 425
Publication date: 5th February 2015

Tetrapyrrole macrocycles are amongst the most promising light acceptors in organic photovoltaic (OPV) devices, in which they act both as “antenna” molecule, i.e., by absorbing light in the visible range, and as electron donor or acceptor once excited.^1,2 In recent studies, the preparation of photoactive nanohybrids formed by phthalocyanine or porphyrin macrocycle with either single-wall carbon nanotubes (SWNTs)³ or graphene sheets⁴ has been investigated.In these nanocomposites, the macrocycles are linked to the carbon surface either by covalent bonds or by noncovalent supramolecular pi-pi interactions,⁵ the latter being often mediated by the presence of pyrene units. Driven by the need for light acceptors leading to OPV devices with increased efficiency, we focused on pyrene derivatives of thio-alkylporphyrazines. This class of tetrapyrrole macrocycles, which displayed applications as liquid-crystals⁶ and materials for non-linear optics,⁷ has been never studied before in OPV. With this aim, we synthesized a new pyrene-substituted thio-ethylporphyrazine 1 (Figure) exploiting the Suzuki-Miyaura cross-coupling reaction⁸. In this compound the pyrene unit can promote the formation of nanohybrids with SWNTs or graphene and, being directly bonded to the macrocycle ß-position, might facilitate an effective electronic interaction between the two donor-acceptor units in the hybrid composite. We herein describe the synthesis of compound 1, along with its spectroscopic and electrochemical characterization. Nanohybrids resulting by noncovalent interaction of 1 with SWNTs were prepared, carrying out microscopy analyses and preliminary electrochemical measurements on photocurrent generation. Moreover, nanohybrids with graphene were made by mixing in solution the compound 1 with graphene flakes, which were previously prepared by liquid phase exfoliation of graphite. The nanocomposite material was characterized by SEM, TEM, Raman and absorption spectroscopy. A planar diode was fabricated by depositing the nanocomposite on glass between two metal electrodes. The IV characteristics of the diode were evaluated in dark and under light illumination.
Structure of the studied compound 1.
1. Walter, M. G.; Rudine, A. B.; Wamser, C. C. Porphyrins and Phthalocyanines in Solar Photovoltaic Cells. J. Porphyrins Phthalocyanines 2010, 14, 759–792. 2. Calogero, G.; Bartolotta, A.; Di Marco, G.; Di Carlo, A.; Bonaccorso, F. Vegetable-based Dye-Sensitized Solar Cells. Chem. Soc. Rev. 2015, DOI:10.1039/c4cs00309h. 3. Ince, M.; Bartelmess, J.; Kiessling, D.; Dirian, K.; Martìnez-Dìaz, M. V.; Torres, T.; Guldi, D. M. Immobilizing NIR Absorbing azulenocyanines onto single wall carbon nanotubes—from charge transfer to photovoltaics. Chem. Sci. 2012, 3, 1472-1480. 4. Roth, A.; Ragoussi, M.-E.; Wibmer, L.; Katsukis, G.; de la Torre, G.; Torres, T.; Guldi, D. M. Electron-Accepting Phthalocyanine–Pyrene Conjugates: Towards Liquid Phase Exfoliation of Graphite and Photoactive Nanohybrid Formation with Graphene. Chem. Sci. 2014, 5, 3432-3438. 5. Bottari, G.; de la Torre, G.; Guldi, D.M.; Torres, T. Covalent and Noncovalent Phthalocyanine-Carbon Nanostructure Systems: Synthesis, Photoinduced Electron Transfer, and Application to Molecular Photovoltaics. Chem Rev. 2010, 111, 6768-6816. 6. (a)Belviso, S.; Ricciardi, G.; Lelj, F. Inter-ring interactions and peripheral tail effects on the discotic mesomorphism of `free-base' and Co(II), Ni(II) and Cu(II) alkenyl(sulfanyl) porphyrazines. J. Mater. Chem. 2000, 10, 297–304. (b) Belviso, S.; Amati, M.; De Bonis, M.; Lelj, F. Columnar Discotic Mesophases from Novel Non-symmetrically Substituted (Octylsulfanyl) Porphyrazines. Mol. Cryst. Liq. Cryst. 2008, 481, 56–72. 7. Belviso, S.; Amati, M.; Rossano, R.; Crispini, A.; Lelj, F. Non-Symmetrical Aryl- And Arylethynyl-Substituted Thioalkyl-Porphyrazines for Optoelectronic Materials: Synthesis, Properties, and Computational Studies. Dalton Trans. 2015, 44, 2191-2207 and references therein. 8. Miyaura, N.; Suzuki, A. Palladium-Catalyzed Cross-Coupling Reactions of Organoboron Compounds. Chem. Rev. 1995, 95, 2457–2483.

© FUNDACIO DE LA COMUNITAT VALENCIANA SCITO