A New Efficient Method for Calculation of Frenkel Exciton Parameters in Molecular Aggregates

The Frenkel exciton Hamiltonian is at the heart of many simulations of excitation energy transfer in molecular aggregates. It separates the aggregate into Coulomb-coupled monomers. Here it is shown that the respective parameters, i.e. monomeric excitation energies and Coulomb couplings between transition densities, can be efficiently calculated using time-dependent tight-binding-based density functional theory (TD-DFTB). Specifically, Coulomb couplings are expressed in terms of self-consistently determined Mulliken transition charges. The determination of the sign of the coupling requires an additional super-molecule calculation. The approach is applied to two dimer systems. First, formaldehyde oxime for which a detailed comparison with standard DFT using the B3LYP and the PBE functionals is provided. Second, the Coulomb coupling is explored in dependence on the intermolecular coordinates for a perylene bisimide dimer. This provides structural evidence for the previously observed biphasic aggregation behavior of this dye

Mapping long-lived dark states in copper porphyrin nanostructures

Long-lived excited states in molecular aggregates are a promising route for efficient energy transfer with potential applications in optoelectronic devices. Spatially resolved optical detection of these states is challenging due to a critical trade-off between sufficiently high photon emission rates and negligible contribution of the luminescence channel to the total lifetime. Here, we report on selective mapping of excited states in copper tetraundecylporphyrin (CuTUP) assemblies on graphite (HOPG) using two-photon photoemission electron microscopy. While the photoemission electron microscopy (PEEM) data are consistent with time-resolved luminescence measurements on a nanosecond time scale, additional long-lived states with lifetimes in the microsecond range are found with nondetectable emission of photons. These,dark states serve as initial states in a subsequent photoemission process, giving rise to a high yield and, pronounced lateral contrast. In combination with long-range corrected density functional theory (DFT) we analyze the energetics and nature of contributing states. Our study underlines the versatility and specificity of excitation nanoscopy by PEEM enabling high spatial resolution beyond the wavelength limit

Luminescence sensing and imaging:general discussion

Faraday Discussion on Supramolecular Photochemistr

Natural and artificial photosynthesis: general discussion

34sinot availablereservedmixedBohne, C.; Pan, Q.; Ceroni, P.; Börjesson, K.; Rohacova, J.; Lewis, F.; Vlcek, A.; Bassani, D. M.; Würthner, F.; Sartorel, A.; de Silva, A. P.; Nocera, D.; Scandola, F.; Lemon, C.; Allain, C.; Brudvig, G. W.; Marchesan, Silvia; Sundstrom, V.; Campagna, S.; Sheehan, S. W.; Plötz, P.; Monti, F.; Kelly, J. M.; Gibson, E.; Maneiro, M.; Harriman, A.; Ruggi, A.; Galoppini, E.; Thummel, R.; Weinstein, J.; Vos, J.; Ishitani, O.; Gust, D.; Díaz-Moscoso, A.Bohne, C.; Pan, Q.; Ceroni, P.; Börjesson, K.; Rohacova, J.; Lewis, F.; Vlcek, A.; Bassani, D. M.; Würthner, F.; Sartorel, A.; de Silva, A. P.; Nocera, D.; Scandola, F.; Lemon, C.; Allain, C.; Brudvig, G. W.; Marchesan, Silvia; Sundstrom, V.; Campagna, S.; Sheehan, S. W.; Plötz, P.; Monti, F.; Kelly, J. M.; Gibson, E.; Maneiro, M.; Harriman, A.; Ruggi, A.; Galoppini, E.; Thummel, R.; Weinstein, J.; Vos, J.; Ishitani, O.; Gust, D.; Díaz Moscoso, A