Review—Two Different Multiple Photosynthetic Reaction Centers Using Either Zinc Porphyrinic Oligopeptide-Fulleropyrrolidine or Free-Base Porphyrinic Polypeptide-Li+@C60 Supramolecular Complexes

Nathalie Solladié,Kei Ohkubo,Suresh Gadde,Francis D’Souza,Régis Rein,Vincent Troiani,Kenji Saito,Hongjin Qiu,Tetsuya Hasegawa,Shunichi Fukuzumi

doi:10.1149/2162-8777/abaaf5

Abstract

An overview of two successful examples of photosynthetic reaction center models combined with light-capturing antenna chromophores is presented. In the first example, supramolecular complexes are formed between flexible zinc porphyrinic oligopeptides and fulleropyrrolidine bearing either a pyridine or imidazole functionalized C60 via a coordination bond plus π−π interactions. The excited energy migration occurs between porphyrin units followed by charge separation. The charge separation (CS) lifetimes of the supramolecular oligopeptide complexes have been elongated by increasing the generation of the porphyrins, enabling us to attain the longest lifetime (0.84 ms) for the P(ZnP)8-ImC60 supramolecular system in PhCN solution at 298 K, ever reported for supramolecular complexes. In the second example, free-base porphyrin polypeptides (P(H2P)n; n = 4 and 8) form supramolecular complexes with Li+@C60 in PhCN, in which the binding is much stronger than C60. Efficient energy migration occurs between porphyrins in P(H2P)n. The triplet CS states derived from 3Li+@C60 had long lifetimes due to spin-forbidden back electron transfer. The triplet CS lifetime becomes longer upon increasing the number of H2P due to the charge migration among porphyrins. The present study provides valuable insight into the energy and electron transfer processes leading to long-lived charge separated states in artificial photosynthetic antenna-reaction center models.

Highlights

In natural photosynthetic systems, the solar energy is collected by pigment molecules attached to the light harvesting complexes
Metal centres were required for the construction of supramolecular complexes between porphyrins acting as light harvesting units and electron acceptors containing Lewis base ligands for coordination to the metal centres.[36–44]
Multiple photosynthetic reaction centers using zinc porphyrinic oligopeptide–fulleropyrrolidine supramolecular complexes.—We first synthesized multiple photosynthetic reaction centers composed of light-harvesting multiporphyrin units and charge-separation units, which have been combined by using non-covalent binding including coordination bond and π−π interaction

Summary

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Review—Two Different Multiple Photosynthetic Reaction Centers Using Either Zinc Porphyrinic Oligopeptide-Fulleropyrrolidine or Free-Base Porphyrinic Polypeptide-Li+@C60 Supramolecular Complexes. The solar energy is collected by pigment molecules attached to the light harvesting complexes In these units, the chlorophylls are held in a favored spacing and orientation by fairly short α-helical polypeptides.[1–3]. Among multi-porphyrin arrays, porphyrin oligomers with oligopeptidic backbones in which porphyrins are held in a favored spacing and orientation by fairly short helical oligopeptides have merited special attention in relevance to the natural light-harvesting complex in which chlorophyll and oligopeptides are well-organized in the protein.[65,66]. We highlight in this mini-review the elaboration of two different multiple photosynthetic reaction centres using either zinc. Porphyrinic oligopeptide–fulleropyrrolidine or free-base porphyrinic polypeptide–Li+@C60 supramolecular complexes

Results and Discussion

The laser flash photolysis of the supramolecular complexes of

Conclusions