Energy Transfer and Spectroscopic Characterization of Multichromophoric Assemblies

Abstract

The description and interpretation of electronic spectra of aggregates and the relationship of these quantities to the electronic transfer matrix element for energy transfer between its components are examined. An analysis of higher multipole interactions in the Coulombic integral as well as an introduction to the consequence of the “through-configuration” interaction (involving interchromophore charge transfer states) on spectral shifts, band intensities, and radiative rates is presented. It is found that as higher multipole contributions become significant in comparison with the dipole−dipole interaction, short-range, interchromophore orbital overlap (IOO) dependent interactions often become much greater than the higher multipole corrections to the dipole−dipole interaction. It is shown that IOO effects due to the through-configuration interaction may be evident in the absorption spectra of molecular aggregates as hypochromism or hyperchromism. It is postulated that fluorescence lifetime data for a single chromophore as compared to a dimer should convey information regarding the strength of the electronic coupling in the lowest excited state. The analysis of interactions that lead to interchromophore energy transfer or delocalization in photosynthetic light harvesting complexes, monolayer assemblies, and bichromophores is discussed.

UV Spectra and Excitation Delocalization in DNA: Influence of the Spectral Width

“…Quantum-chemical calculations performed for stacked aromatic molecules have shown that orbital overlap interactions may be of the order of one hundred wavenumbers. [14][15][16][17][18][19][20][21][22][23][24][25][26][27] A very rough estimation of the combined action of dipolar coupling and orbital-overlap interactions, can be made by adding a constant term of 100 cm À1 to the off-diagonal terms corresponding to nearest neighbors. For a base n, we considered the bases nÀ1 and n + 1 on the same strand, and the bases 20Àn, 21Àn and 22Àn on the opposite strand as nearest neighbors.…”

“…Finally, charge-transfer interactions, neglected here, are expected to induce a bathochromic shift of the duplex spectrum as well as a change in the oscillator strength. [15] In spite of the above limitations, the calculated spectra of (dA) 10 . (dT) 10 allows us to show the effect of the formation of delocalized excited states due to dipolar coupling.…”

“…New methodologies, introducing quantum chemistry methods in the calculation of the diagonal and off-diagonal terms, were applied in the investigation of various systems such as molecular aggregates and photosynthetic antennas (see for example refs. [13][14][15][16][17][18]). Thus, subtle differences appeared in the properties of various systems and the effect of structural disorder could be evaluated.…”

Triplet transport in thin films: fundamentals and applications

“…These ionic, charged intermediates result in the same exponential dependence on donor and acceptor distance, described by the original 'Dexter-type' model. [48][49][50] In other words, TET across short bridges with high tunnelling barriers involves either sequential or simultaneous transfer of ionic intermediates. 51 Formally, the matrix element for Dexter transfer is proportional to the square of the orbital overlap between the donor and acceptor, as shown in eqn (5), but for charge transfer, it is proportional to the orbital overlap only.…”

Damping and higher multipole effects in the quantum electrodynamical model for electronic energy transfer in the condensed phase

“…This was investigated recently for various model dimer separations. 6,37 Examination of the form for the coupling tensors for the electric-magnetic cross terms Ep -M q, VЈ, shows that the interaction depends always upon , even in the near zone. Thus these constitute examples of ''entirely retarded'' couplings.…”