Excitation energy transfer and two-dimensional spectra of porphyrin nanorings

Synthetic meso–meso linked porphyrin nanorings are promising systems for studying exciton dynamics and energy transfer processes due to their structural similarity to natural light-harvesting complexes, recent experimental works have been shown to exhibit excitation energy transfer on the same timescale and length scale as the natural light-harvesting complex LH2 and with comparable efficiency. In this talk I will explain how we employed a combination of different methods to thoroughly investigate these nanorings, focusing on exciton dynamics in such systems. We characterized the coupling between the solvent environment and the vertical excitation energies of the nanoring chromophores, using time-dependent density functional theory over a 12 ps long molecular dynamics trajectory, determining spectral densities from the temporal autocorrelation functions of the energy gaps. With this characterization of the system and the environment, the excitonic dynamics and the 2D electronic spectrum of the system were calculated using Redfield theory, revealing details about the exciton energy transfer processes. The cross peaks provided valuable insights into the coherent and incoherent energy transfer mechanisms within the nanorings, highlighting key features of exciton migration and localization. This integrated approach deepens our understanding of exciton dynamics in porphyrin nanorings and opens new avenues for their application in artificial photosynthetic systems.