DNA‐Organized Light‐Harvesting Antennae: Energy Transfer in Polyaromatic Stacks Proceeds through Interposed Nucleobase Pairs

Abstract

DNA‐based light‐harvesting antennae with varying arrangements of light‐absorbing phenanthrene donor units and a pyrene acceptor dye were synthesized and tested for their light‐harvesting properties. Excitation of phenanthrene is followed by rapid transfer of the excitation energy to the pyrene chromophore. A block of six light‐absorbing phenanthrenes was separated from the site of the acceptor in a stepwise manner by an increasing number of intervening AT base pairs. Energy transfer occurs through interposed AT base pairs and is still detected when the phenanthrene antenna is separated by 5 AT base pairs.

DNA-organized artificial LHCs – testing the limits of chromophore segmentation

“…In fact, the fluorescence quantum yield even slightly increased by going from a continuous chromophore stack to a bi-segmental arrangement. 13 The present study shows that the efficiency of energy transfer in multi-segmental phenanthrene arrangements, in which phenanthrenes and DNA base pairs are arranged in an alternating fashion (see Fig. 1 for an illustration), is not only maintained but even grows until it reaches a maximum after three to four segments.…”

“…[1][2][3][4][5][6][7][8][9][10][11][12] The defined positioning of chromophores in a framework is an important aspect in the design of artificial light-harvesting complexes (LHCs). [13][14][15][16][17][18][19][20][21][22] In such systems, light is collected by precisely arranged donor chromophores and the absorbed energy is transferred to a suitable acceptor. [23][24][25][26][27][28][29][30] The light-harvesting properties resulting from the supramolecular assembly of phenanthrene and pyrene molecules within the scaffold of the DNA duplexes was demonstrated before.…”

“…Transient absorption spectroscopy indicates that the energy is transferred over a delocalized excited state of the phenanthrenes. 13 Subsequent studies showed that excitation energy transfer also takes place if the aromatic stack of phenanthrenes is divided into two segments by intervening base pairs. Excitation energy is still efficiently transmitted along the phenanthrene antenna if the latter is interrupted by up to three DNA base pairs.…”

A posteriori localization of many‐body excited states through simultaneous diagonalization

“…As a prototypical example, linear arrangements of π ‐stacked phenanthrenes and pyrenes embedded in a DNA scaffold were shown experimentally to transport excitons over large distances after photoexcitation, up to 150 nm. These have great potential as quasi‐1D antennas to be used in photon‐harvesting and as transmitting nanodevices 7 . Studying coherent energy transport in such systems requires the description of excitons delocalized over the whole structure of the device.…”

“…These have great potential as quasi-1D antennas to be used in photon-harvesting and as transmitting nanodevices. 7 Studying coherent energy transport in such systems requires the description of excitons delocalized over the whole structure of the device. Yet, to rationalize such non-local phenomena, it is often preferable to work with a local description of the electronic structure.…”