Directed Energy Transfer Funnels in Dendrimeric Antenna Supermolecules

Abstract

We have studied the dynamics of directed, multistep energy transport in a class of fractal-like dendrimeric molecules. For particular forms of these highly branched phenylacetylene dendrimers, both theory and experiment put the lowest excitation energy at the center (locus) of the supermolecule. This results in a structurally symmetric and ordered exciton funnel, with a well-directed energy gradient. We have designed and synthesized a derivative of these dendrimers with a perylene moiety at the locus, which acts as an energy trap for the directed exciton funnel. Spectroscopic evidence indicates transfer efficiency of 98% from the photoabsorbing dendrimer backbone to the perylenic trap.

Nonadiabatic Molecular Dynamics Simulations of the Energy Transfer between Building Blocks in a Phenylene Ethynylene Dendrimer

“…[8][9][10][11][12][13] Since they can be prepared with high regularity and controlled molecular weights, 14 dendrimers offer great promise in the control of energy funneling. Their successful directional-energy transfer has been studied by Moore et al, 15,16,9,17 who have reported the syntheses of a peryleneterminated dendrimer, called the nanostar. This molecule presents four generations of linear PPE segments with decreasing lengths toward the periphery, creating an efficient energy funnel toward the perylene trap.…”

“…As a result, the excitons in the nanostar are localized on each PPE segment, 9 and its overall absorption spectrum can be interpreted as the sum of these individual contributions. 15,10,17 Theoretical interest in PPE dendrimers arises from the possibility of analyzing them as an ensemble of individual coupled chromophore units. Therefore, the system can be described using the Frenkel exciton Hamiltonian 18,19 with Coulombic coupling between excitations localized on the linear units.…”

Exciton confinement in organic dendrimer quantum wells for opto-electronic applications

“…[1][2][3][4][5][6][7][8][9][10][11] Rather than employing a linear geometry like in polymers, dendrimers are based on a self-similar fractal branching geometry, where the amount of branching increases with the size of the molecule. Through elegant synthetic routes it has been possible to create large, almost nanoscale molecules with a wide range of functional properties ranging from molecular recognition, such as in drug delivery systems 1 to artificial light-harvesting antennae.…”

“…Through elegant synthetic routes it has been possible to create large, almost nanoscale molecules with a wide range of functional properties ranging from molecular recognition, such as in drug delivery systems 1 to artificial light-harvesting antennae. 3,4,9 A particularly interesting area of applications is in optoelectronic devices such as light-emitting diodes ͑LEDs͒, where dendrimers have been used both as emitting layers 6,7,10 and as charge transport layers. 11,12 The well defined chemical structure of dendrimers allows a systematic correlation to be drawn between the device properties and the dendrimer structure.…”

Principles of Directed Electronic Energy Transfer

“…Striking examples of this principle can be seen in classic work on perylene-functionalised phenylacetylene dendrimers [35,36]. An example of a organosilicon cationic dendrimer is given in figure 6.…”