Quinoxaline-based and pyrazine-based organic dyes as anodic sensitizers in photoelectrochemical cells Xheila Yzeiri a,b , Nicola Sangiorgi c , Francesca Gambassi d , Andrea Barbieri d , Massimo Calamante b,e , Daniele Franchi b , Carmen Coppola a,b, f , Adalgisa Sinicropi a,b, f , Barbara Ventura d , Alessandro Mordini b,e , Alessandra Sanson c , Lorenzo Zani b a Department of Biotechnology, Chemistry and Pharmacy, University of Siena, Via A. Moro 2, 53100, Siena, Italy, b Institute of Chemistry of Organometallic Compounds (CNR-ICCOM), Via Madonna del Piano 10, 50019, Sesto Fiorentino, Italy, c Institute of Science, Technology and Sustainability for Ceramics (CNR-ISSMC), Via Granarolo 64, 48018, Faenza, Italy, d Institute for Organic Synthesis and Photoreactivity (CNR-ISOF), Via P. Gobetti 101, 40129, Bologna, Italy, e Department of Chemistry “U. Schiff”, University of Florence, Via della Lastruccia 13, 50019, Sesto Fiorentino, Italy, f Consorzio per lo Sviluppo dei Sistemi a Grande Interfase (CSGI), Via della Lastruccia 3, 50019, Sesto Fiorentino, Italy In light of the current climate crisis and the growing scarcity of resources, there is an urgent need for innovative strategies to produce fuels, chemicals, and materials from renewable sources. To ensure a sustainable future, it is essential to develop efficient transformations that rely solely on renewable energy and minimize the emission of hazardous substances. Photocatalysis, as a direct sunlight-driven process, presents a promising approach to achieving a sustainable economy by facilitating both the synthesis and chemical recycling of diverse chemicals, materials, and fuels. The use of light to generate excited states enables thermodynamically uphill reactions, laying the foundation for solar energy storage in fuels. Additionally, photocatalysis allows access to novel reaction pathways through excited-state reactivity, which are unattainable via conventional ground-state catalytic mechanisms. We explore the application of photocatalytic processes in the field of artificial photosynthesis. The core of the research focuses on Dye-Sensitized Photoelectrochemical Cells (DS-PECs) for water splitting, a promising technology for converting solar energy into chemical energy. In this system, sunlight is absorbed by a dye and used to drive the photo-oxidation of water, catalyzed by a water oxidation catalyst (WOC), to produce 'solar' fuels such as hydrogen (H 2 ). The research involved the design, synthesis, and characterization of novel metal-free organic dyes. Two families of donor-auxiliary acceptor-π-acceptor (D-A-π-A) sensitizers were developed: compound based on 2,3-diphenylquinoxaline core ( 1a-c ) 1 , and compounds incorporating a 2,3-diphenylpyrido[3,4-b]pyrazine core ( PP2a-c) . These dyes were successfully synthesized and thoroughly characterized through spectroscopic and electrochemical methods. Photoelectrochemical tests in a three- electrode cell evaluated the anodic sensitization capabilities of compounds 1a-c , with compound 1a exhibiting the highest photocurrent generation. Further research extended beyond conventional co-loading approaches by developing an innovative dye/catalyst photoanode-sensitization strategy. This involved designing a novel metal-free sensitizer-catalyst covalent adduct (dyad), based on the structure of dye 1a , and modifying it to facilitate coordination with the Ru(bda) WOC. The resulting dyad was successfully synthesized and its structure was confirmed through comprehensive spectro- electrochemical characterization. References 1. Yzeiri, X; Sangiorgi, N.; Gambassi, F.; Barbieri, A.; Calamante, M.; Franchi, D.; Coppola, C.; Sinicropi, A.; Ventura, B.; Mordini, A.; Sanson, A.; Zani, A. Dyes and Pigments 2025, 232,112455.
P18
© The Author(s), 2025
Made with FlippingBook Learn more on our blog