Multiscale Modeling of Molecular Structure and Optical Properties of Complex Supramolecular Aggregates

Abstract

<div> <div> <div> <p>Supramolecular aggregates of synthetic dye molecules offer great perspectives to prepare biomimetic functional materials for light-harvesting and energy transport. The design is complicated by the fact that structure-property relationships are hard to establish, because the molecular packing results from a delicate balance of interactions and the excitonic properties that dictate the optics and excited state dynamics, in turn sensitively depend on this packing. Here we show how an iterative multiscale approach combining molecular dynamics and quantum mechanical exciton modeling can be used to obtain accurate insight into the packing of thousands of cyanine dye molecules in a complex double-walled tubular aggregate in close interaction with its solvent environment. Our approach allows us not only to answer open questions on the structure of these prototypical aggregates, but also about their molecular-scale structural and energetic heterogeneity, and the microscopic origin of their photophysical properties. This opens the route to accurate predictions of energy transport and other functional properties.<br></p> </div> </div> </div>

Structural characterization of supramolecular hollow nanotubes with atomistic simulations and SAXS

“…Both experimental and theoretical studies would greatly benefit from an explicit atomistic description of the monomer position and arrangement. 67 Our approach of constructing such complex systems and our findings on the dimensions of these aggregates pave the way for simulating more complex processes, such as the self-assembly of the C8S3 nanotubes or the formation of bundles, whose mechanisms are still not fully understood.…”

Molecular versus Excitonic Disorder in Individual Artificial Light-Harvesting Systems

“…We built on recent work where a combination of molecular dynamics (MD) simulations and quantum mechanical exciton modeling was used to calculate the structure and the linear absorption spectrum of the double-walled C8S3 nanotubes in interaction with the surrounding solvent. 29 Using this model as a starting point, we ran an MD simulation to generate a time sequence of configurations of the entire nanotube and solvent at 10 fs intervals. From these configurations, we obtained the optical transition energies ω n ( t ) of individual C8S3 molecules as a function of time using microelectrostatic calculations as well as the intermolecular excitation transfer interactions J nm ( t ) ( n and m label the molecules in a particular wall of the nanotube) using the extended dipole model ( Methods section).…”

“…We used a recently developed large-scale atomistic model of the C8S3 double-walled nanotube. 29 The initial structures were obtained by constructing 2D lattices from a unit cell in which the C8S3 molecules were arranged in a herringbone formation. The lattices were then rolled into cylindrical shapes and put together to create double-walled structures that maintained their tubular formation.…”

“…The lattices were then rolled into cylindrical shapes and put together to create double-walled structures that maintained their tubular formation. (For more details, see refs ( 29 ) and ( 65 ).) The nanotube model is 100 nm long, corresponding to 7024 C8S3 molecules, and solvated in water and Na + counterions.…”

“… 4 , 25 , 26 The interpretation of these experiments, which provide increasingly detailed information, has also triggered the development of new theoretical and computational approaches that are able to model the exciton energetics and dynamics of large molecular assemblies in interaction with a complex and fluctuating embedding matrix (such as a solvent or a protein scaffold). 27 − 29 …”