Adapting the Förster Theory of Energy Transfer for Modeling Dynamics in Aggregated Molecular Assemblies

Abstract

The remarkable efficiencies of solar energy conversion attained by photosynthetic organisms derive partly from the designs of the light-harvesting apparatuses. The strategy employed by nature is to capture sunlight over a wide spectral and spatial cross section in chromophore arrays, then funnel the energy to a trap (reaction center). Nature's blueprint has inspired the conception of a diversity of artificial light-harvesting antenna systems for applications in solar energy conversion or photonics. Despite numerous, wide-ranging studies, truly quantitative predictions for such multichromophoric assemblies are scarce because Fo ¨rster theory in its standard form often seems to fail. We report here a new framework within which energy transfer in molecular assemblies can be modeled quantitatively using a generalization of Fo ¨rster's theory. Our results show that the principles involved in optimization of energy transfer in confined molecular assemblies are not revealed in a simple way by the absorption and emission spectra because such spectra are insensitive to length scales on the order of molecular dimensions.

The feasibility of coherent energy transfer in microtubules

“…However, as the interdimer spacing of Trps is uninterrupted (figure 4), it is feasible that such an arrangement could effectively transfer energy along the protofilament length via a combination of coherent tunnelling and incoherent relaxation/excitation. Additionally, the unique cylindrical lattice symmetries found [36], induced by geometrical symmetries, can enhance the exciton diffusion length along cylindrically symmetric structures [37], similar to the helical arrangement of tubulin, and its chromophores, in microtubules.…”

Excitation Energy Transfer between Closely Spaced Multichromophoric Systems: Effects of Band Mixing and Intraband Relaxation

“…18,19,20,21,22,23,24,34 We have focused, however, on two other aspects specific to multichromophoric systems, namely the effects of band mixing and intraband relaxation on the energy transfer. The first has been studied by comparison of the perturbative and the nonperterbative method.…”

“…20,21,22,23,24,34 We note that in Refs. 18 and 19 the problem was treated in a more general way than we did above: only the transfer interactions J DA nm were considered as perturbations, while the exciton-bath couplings were accounted for by a selfconsistent second-order evaluation of the self-energy.…”

“…This problem has drawn particular attention in the context of excitation energy transfer from the B800 to the B850 ring of the photosynthetic antenna system LH2. 18,19,20,21,22,23,24 The first complication when dealing with systems of strongly interacting chromophores is that their excited states are excitons, consisting of a coherent superposition of the excited states of many molecules. Due to their spatial extent, which may easily exceed the separation between the two systems, the effective interaction between an exciton state on the donor system and one on the acceptor system cannot be modelled as the interaction between the transition dipoles of both states.…”

Ultrafast energy transfer with competing channels: Non-equilibrium Förster and Modified Redfield theories

“…In molecular complexes, simple predictions of the Förster theory often fail [14][15][16], but generalizations of the original ideas to interactions between the whole molecular complexes is straightforward [14,17,18]. Similarly, Redfield equations adapted for molecular aggregates proved to be an extremely versatile tool [1,2,19].…”