Light‐Harvesting Nanotubes Formed by Supramolecular Assembly of Aromatic Oligophosphates

Abstract

A 2,7‐disubstituted phosphodiester‐linked phenanthrene trimer forms tubular structures in aqueous media. Chromophores are arranged in H‐aggregates. Incorporation of small quantities of pyrene results in the development of light‐harvesting nanotubes in which phenanthrenes act as antenna chromophores and pyrenes as energy acceptors. Energy collection is most efficient after excitation at the phenanthrene H‐band. Fluorescence quantum yields up to 23 % are reached in pyrene doped, supramolecular nanotubes.

Supramolecular Assembly of DNA-Phenanthrene Conjugates into Vesicles with Light-Harvesting Properties

“…For this purpose, the vesicles were doped by addition of the pyrene-containing oligomer 5 (Figure 3), which was previously shown to function as an acceptor in supramolecular phenanthrene nanotubes. 71 Phenanthrene emission (378 and 398 nm) decreases, whereas pyrene emission (412, 435, and 462 nm) grows. No mentionable pyrene emission occurred if the experiment was performed in the absence of spermine tetrahydrochloride but otherwise identical conditions (see Supporting Information, Figure S3).…”

“…Two isosbestic points are observed at 285 nm and 322 nm. Significant changes are also observed in the region from 240 -280 nm, where phenanthrene also shows significant absorption (λmax ~ 274 nm 71 ). This strongly indicates hybridization of the two complementary single strands and, at the same time, aggregation of the phenanthrene units.…”

“…[51][52][53][54][55][56][57][58][59][60][61][62][63][64][65][66][67][68] We recently described the light-harvesting properties of phenanthrene arrays in DNA-based scaffolds, 55,69 supramolecular fibres 70 or nanotubes. 71 Here, we present the formation and characteristics of lightharvesting vesicles assembled from DNA-phenanthrene conjugates. Table 1 shows the DNA strands used for this study.…”

“…In combination with pyrene as an acceptor chromophore, the phenanthrene assemblies act as lightharvesting antennae (LHA). 55,[69][70][71] In order to test if the vesicles assembled from oligomers 1 and 2 also act as LHAs, they were subjected to incorporation of small quantities of pyrene molecules. For this purpose, the vesicle were doped by addition of the pyrene-containing oligomer 5 (Figure 3), which was previously shown to function as an acceptor in the context of tubular phenanthrene supramolecular polymers.…”

“…For this purpose, the vesicle were doped by addition of the pyrene-containing oligomer 5 (Figure 3), which was previously shown to function as an acceptor in the context of tubular phenanthrene supramolecular polymers. 71 Figure 3 (top) shows the effect of addition of 1% of pyrene per phenanthrene on the fluorescence spectrum.…”