Excitation energy transfer in multiporphyrin arrays with cyclic architectures: towards artificial light-harvesting antenna complexes

Abstract

Since highly symmetric cyclic architecture of light-harvesting antenna complex LH2 in purple bacteria was revealed in 1995, there has been a renaissance in developing cyclic porphyrin arrays to duplicate natural systems in terms of high efficiency, in particular, in transferring excitation energy. This tutorial review highlights the mechanisms and rates of excitation energy transfer (EET) in a variety of synthetic cyclic porphyrin arrays on the basis of time-resolved spectroscopic measurements performed at both ensemble and single-molecule levels. Subtle change in structural parameters such as connectivity, distance, and orientation between neighboring porphyrin moieties exquisitely modulates not only the nature of interchromophoric interactions but also the rates and efficiencies of EET. The relationship between the structure and EET dynamics described here should assist a rational design of novel cyclic porphyrin arrays, more contiguous to real applications in artificial photosynthesis.

Supramolecular Organization of Porphyrins and Phthalocyanines by Use of Biomimetic Coordination Methodology

“…[88][89][90] Schugar and coworkers reported that a cyclic array of hexameric Zn-porphyrin 30 6 formed through head-to-tail nitrogen-to-zinc coordination in a single crystal, although a self-coordinating dimer 30 2 was assembled in solution (Scheme 15). 91 So far, the control of the internal angle of ligand-appended porphyrin has rarely been successful in designing large macrocyclic wheels.…”

“…The experimental procedures, how to evaluate and analyze the experimental results, and covalently linked porphyrin arrays are welldocumented in a review by Kim and coworkers. 89 A multichromophore array with energy cascade can direct sequential photoexcited energy flow. Weiss and coworkers arranged boron dipyrromethene (BOD-IPY)-Zn porphyrin-free base porphyrin as an energy cascade array 91·92 based on a phenanthroline-strapped porphyrin, which recognizes an imidazolyl group inside the strap.…”

Understanding excitation energy transfer in metalloporphyrin heterodimers with different linkers, bonding structures, and geometries through stimulated X-ray Raman spectroscopy

“…1 This stimulates researchers to synthesis cyclic porphyrin arrays to achieve high EET efficiency. 32,33 …”

Time resolved structural dynamics of butadiyne-linked porphyrin dimers

“…However, this also restricts the conjugation length and therefore is not the best solution for certain applications 12 . For an efficient “through bond” charge transport, it is preferable that the porphyrin rings show an extended π-orbital communication (conjugation) 13 .…”