(Invited) A Carbon Nanotube Binding Bis(pyrenylstyryl)Bodipy-C60 Nano Tweezer: Formation and Photoinduced Charge Separation in Supramolecular C60-Bodipy-SWCNT Triads

Electron donor-acceptor hybrids comprised of single-wall carbon nanotubes (SWCNT) are promising functional structures having direct applications in energy conversion schemes and molecular optoelectronics. For building such hybrids and exfoliation of SWCNTs, the p-stacking ability of large aromatic compounds such as pyrene is one of the commonly employed approaches. Often, the desired donor or acceptor entities are functionalized to carry one or more pyrene entities and allowed to interact with CNTs. As a suitable electron donor, BODIPYs stand out owing to their ease of structural modifications and rich spectral and redox properties. Consequently, several donor-acceptor conjugates comprised of BF2-chelated dipyrromethene, BODIPY, and the well-known electron acceptor, C60 have been developed. In the present study, we have newly synthesized a nano tweezer comprised of covalently linked BODIPY-C60 carrying two pyrenylstyryl arms, 1. Compound 1 is further allowed to interact with SWCNT(6,5) and SWCNT(7,6) to form the supramolecular C60-BODIPY-SWCNT triads. Upon spectral, electrochemical, and computational characterization, pump-probe spectroscopic studies covering a wide femto-to-millisecond time scale have been performed to establish the occurrence of photoinduced charge separation. The presence of CNT prolonged the lifetime of the charge-separated states revealing the success of the present molecular design strategy for energy harvesting applications. 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. B. KC, G. N. Lim, and F. D’Souza, ‘Accelerated Charge Separation in Graphene Decorated Multi-Modular Tripyrene-Subphthalocyanine-Fullerene Donor-Acceptor Hybrids,’ Angew. Chem. Int. Ed. 2015, 54, 5088-5092. Barrejon, L. M. Arellano, F. D’Souza, F. Langa, ‘Bidirectional charge transfer in carbon-based hybrid nanomaterials’ Nanoscale, 2019, 11, 14978-14992. Figure 1