Utilizing redox-chemistry to elucidate the nature of exciton transitions in supramolecular dye nanotubes

Abstract

Supramolecular assemblies that interact with light have recently garnered much interest as well-defined nanoscale materials for electronic excitation energy collection and transport. However, to control such complex systems it is essential to understand how their various parts interact and whether these interactions result in coherently shared excited states (excitons) or in diffusive energy transport between them. Here, we address this by studying a model system consisting of two concentric cylindrical dye aggregates in a light-harvesting nanotube. Through selective chemistry we are able to unambiguously determine the supramolecular origin of the observed excitonic transitions. These results required the development of a new theoretical model of the supramolecular structure of the assembly. Our results demonstrate that the two cylinders of the nanotube have distinct spectral responses and are best described as two separate, weakly coupled excitonic systems. Understanding such interactions is critical to the control of energy transfer on a molecular scale, a goal in various applications ranging from artificial photosynthesis to molecular electronics.

Room-Temperature Micron-Scale Exciton Migration in a Stabilized Emissive Molecular Aggregate

“…From the temperature-independent term of the Voight function fit, we estimate the contribution of static energetic disorder to be 115 cm −1 (fwhm), roughly half of previous reports for this system, 10,18 close to the average absorption and emission line width at 5 K. The room temperature line width is the convolution of this static Gaussian line width with the temperature-dependent Lorentzian line width. Using repeated measurements, we find the Lorentzian homogeneous fwhm to be 118 cm −1 at 298 K. The relative quantum yield is plotted on a linear/(log) excitation scale (inset).…”

“…10 Matrix-suspended LHNs are photostable over several days under ambient room light and in air (Figure 1f), enabling temperature-dependent linear and transient optical spectroscopies.…”

Vibronic effects and destruction of exciton coherence in optical spectra of J-aggregates: A variational polaron transformation approach

“…A well-known recent example concerns the coherence of excitons in lightharvesting antenna complexes, such as FMO, and its contribution to the excitation transport efficiency in these systems [42][43][44][45][46][47][48][49][50][51]. Another recent example of interest relates to the coherence between electronic excitations on inner and outer walls of double-walled cylindrical molecular aggregates [52][53][54][55][56][57].…”

Exciton Level Structure and Dynamics in Tubular Porphyrin Aggregates

“…11,[16][17] Tubular aggregates formed by self-assembly of dye molecules represent one of the most promising constructs for biomimetic photosynthetic antenna systems. 5,7,[18][19][20] A prominent example of tubular molecular aggregates is derived from meso-tetra(4-sulfonatophenyl) porphyrin (TPPS4) and provides a biomimetic analogue of the chlorosomes of green sulfur bacteria. 9,[21][22][23][24] The structure of TPPS4 tubular aggregates has been characterized by small angle X-ray scattering, atomic force microscopy (AFM), and cryo-electron microscopy.…”