Excitation Energy Migration in A Dodecameric Porphyrin Wheel

Abstract

Intramolecular excitation energy hopping (EEH) time within a dodecameric porphyrin wheel C6ZA, in which six meso-meso linked zinc(II) diporphyrin (Z2) subunits are bridged by 1,3-phenylene spacers, is deduced by a Förster energy hopping model based on S(1)-S(1) exciton-exciton annihilation and anisotropy depolarization. Under the assumption that the energy hopping sites are six Z2 subunits, two different observables (e.g., exciton-exciton annihilation and anisotropy depolarization times) consistently give the EEH time of 4.0 +/- 0.4 ps via 1,3-phenylene spacer of C6ZA, which is faster than 9.4 ps of linear 2Z2 (1,3-phenylene-linked zinc(II) tetraporphyrin). As a consequence, C6ZA serves as a well-defined two-dimensional model for a light-harvesting complex.

Giant Porphyrin Wheels with Large Electronic Coupling as Models of Light‐Harvesting Photosynthetic Antenna

“…When the Fçrster-type incoherent energy-hopping model is employed for this EET mechanism, the depolarization times are related to the EET time by t depolarization = t EET /3. [21,22] Overall, the EET time constant in C24ZB has been calculated to be 3 11.7 = 35.1 ps (Scheme 5). Interestingly, the slower EET rate in C24ZB relative to that in C12ZA (3.6 ps)…”

Ultrafast Photoinduced Charge Separation in Naphthalene Diimide Based Multichromophoric Systems in Liquid Solutions and in a Lipid Membrane

“…One major motivation was the elaboration of artificial analogues of the light-harvesting complexes of photosynthetic organisms. [1][2][3][4][5][6][7] However, multichromophoric molecules have also been developed for other applications such as, for example, molecular wires, 8,9 single photon sources, 10 logic gates, 11 light stabilizers, 12 fluorescent DNA probes, 13,14 or nonlinear optical materials. 15 The covalent bonding allows the degree of interaction between the chromophoric units to be controlled to some extent.…”

“…In this case, however, a modest interaction between the chromophoric moieties is sufficient to enable efficient excitation energy hopping over the whole system, as observed, for example, in the light-harvesting complexes of photosynthetic bacteria 16 and in many artificial analogues. [1][2][3][4][5][6][7] Although excitation energy hopping is a major process in these systems, photoinduced charge separation (CS) between two chemically identical chromophores can also be operative in some cases. For example, the self-quenching of perylene fluorescence has been shown to lead to the formation of both perylene radical cation and anion.…”

Photoinduced Processes in a Dendritic Zn Porphyrin Structure with a Free‐Base Porphyrin Core

“…To mimic the natural processes, artificial light-harvesting antennae require a great number of chromophore units that are well organized in space and able to transfer the absorbed energy to one specific site with high efficiency. Porphyrins are ideal candidates for the construction of lightharvesting arrays and, in the past decade, many artificial multi-porphyrin systems have been developed, such as linear or linear-branched arrays, [1][2][3][4][5] rings, [6][7][8] windmills, [9] dendrimers, [10,11] and other assemblies. [12,13] Among these, dendritic frameworks appear to be the most promising arrays as they allow site-specific placement of the dye molecules in a three-dimensional hyperbranched treelike fashion, and a good choice of the chromophoric units permit the conveyance of the collected energy toward the central core.…”