A cyanine dye rotaxane porphyrin nanoring complex as a model light harvesting system

TL;DR

This study presents a synthetic nanoring-rotaxane assembly with a cyanine dye and zinc porphyrin that models natural photosynthetic energy transfer, supported by theoretical analysis of excitonic interactions.

Contribution

It introduces a novel supramolecular complex mimicking natural light harvesting systems, with a theoretical model explaining its efficient energy transfer.

Findings

Efficient energy transfer from dye to nanoring observed

Theoretical model reproduces absorption spectrum accurately

Excitonic coupling explains energy transfer efficiency

Abstract

A nanoring-rotaxane supramolecular assembly, with a Cy7 cyanine dye (hexamethylindotricarbocyanine) threaded along the axis of the nanoring, has been synthesized as a model for the energy transfer between the light harvesting complex LH1 and the reaction center in purple bacteria photosynthesis. The complex displays efficient energy transfer from the central cyanine dye to the surrounding zinc porphyrin nanoring. We present a theoretical model that reproduces the absorption spectrum of the nanoring and quantifies the excitonic coupling between the nanoring and the central dye, explaining the efficient energy transfer and elucidating the similarity with structurally related natural light harvesting systems.