(Nanocarbons Division Robert C. Haddon Research Award) Nano Carbons in Mimicking the Early Events of Photosynthetic Reaction Center: ‘Simple’ and ‘Not-so-Simple’ Donor-Acceptor Conjugates

Abstract

Light-induced electron transfer is a key step in solar energy conversion, and a process with myriad relevance in the fields of artificial photosynthesis, photocatalysis, photoconductivity, and photovoltaics. In a donor-acceptor, D-A system, light absorption by a chromophore results in the formation of an excited state species, followed by a charge transfer between an electron donor (D) and an electron acceptor (A) leading to a charge-separated D .+ -A .- species.The optimization of these processes and comprehending their mutual interplay to ultimately achieve charge-separated species is of paramount importance for the development of efficient systems in solar light conversion schemes.The present talk summarizes our research over the years focused on utilizing nano carbons, viz., fullerenes, endohedral fullerenes, carbon nanotubes, and graphene in the construction of donor-acceptor systems capable of undergoing photoinduced energy and electron transfer events. Both, covalently linked with rigid, semi-rigid, flexible, or conjugated spacers, and self-assembled via metal-ligand axial coordination, ion-pairing, ion-dipole, or hydrogen bonding strategies were utilized in the construction of donor-acceptor conjugates. Multi-modular donor-acceptor constructs were designed, synthesized, and studied to probe sequential energy and electron transfer events, finally resulting in long-lived charge-separated states. In some instances, these molecular systems were also used as photocatalytic energy conversion schemes. The pros and cons of utilizing nanocarbon materials as photo-active functional materials will be highlighted. D’Souza, F.; Sandanayaka, A. S. D.; Ito, O. ‘SWNT-Based Supramolecular Nanoarchitectures with Photosensitizing Donor and Acceptor Molecules’ Phys. Chem. Letts. 2010, 1. 2586-2593.D’Souza, and O. Ito ‘Photosensitized electron transfer processes of nano carbons applicable to solar cells,’ Chem. Soc. Rev. 2012, 41, 86-96.B. KC, F. D’Souza, ‘Design and photochemical study of supramolecular donor-acceptor systems assembled via metal-ligand axial coordination Coord. Chem. Rev. 2016, 322, 104-141.Bottari, M. A. Herranz, L. Wibmer, M. Vollard, L. Rodriguez-Perez, D. M. Guldi, A. Hirsch, N. Martin, F. D’Souza, T. Torres, Chemical functionalization and characterization of graphene-based materials, Chem. Soc. Rev. 2017, 46, 4464-4500.Barrejon, L. M. Arellano, F. D’Souza, F. Langa, ‘Bidirectional charge transfer in carbon-based hybrid nanomaterials’ Nanoscale, 2019, 11, 14978-14992.Kazemi, Y. Jang, A. Liyanage, P. A. Karr, and F. D’Souza, ‘A Carbon Nanotube Binding Bis(pyrenylstyryl)BODIPY-C60 Nano Tweezer: Charge Stabilization through Sequential Electron Transfer’, Angew. Chem. Int. Ed. 2022, in press