Bridging the gap between H- and J-aggregates: Classification and supramolecular tunability for excitonic band structures in two-dimensional molecular aggregates

Deshmukh, Arundhati; Geue, Niklas; Bradbury, Nadine C.; Atallah, Timothy; Chuang, Chern; Pengshung, Monica; Cao, Jianshu; Sletten, Ellen M.; Neuhauser, Daniel; Caram, Justin R.

doi:10.1063/5.0094451

Cited by 26 publications

(50 citation statements)

References 59 publications

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“…23 Recent work has shown several extensions of this theory, illustrating that excitonic coupling and thereby, the spectral shifts and the degree of narrowing are sensitive the geometric arrangements of the molecules, nature of various intermolecular interactions, structural and/or energetic disorder, as well as the overall aggregate topology (linear, 2D sheets, tubes etc.). [25][26][27] However, achieving finecontrol over all these parameters requires a high-resolution structure of the underlying supramolecular self-assemblies.…”

Section: Introductionmentioning

confidence: 99%

Near-Atomic Resolution Structure of J-aggregated Helical Light Harvesting Nanotubes

Deshmukh

Zheng

Chuang

et al. 2022

Preprint

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Function-oriented design of supramolecular self-assemblies represents a foundational goal in chemistry. Especially, chromophore self-assemblies display extreme photophysical changes from their monomers that are sensitive to the nanoscale molecular arrangements. Slip-stacked arrangements in J-aggregates lead to red shifts (>200 nm) and enhanced quantum yields. Actively introducing specific molecular arrangements using supramolecular chemistry provides a platform to tune the excitonic couplings and avail exotic photophysical properties. However, the nanoscale molecular arrangements have not yet been directly observed in these solution-state assemblies. Here, we present a high-resolution structure of the prototypical biomimetic light harvesting nanotubes (LHNs) of an amphiphilic cyanine dye (C8S3-Cl). We achieve a 3.3 Å resolution with helical reconstruction of cryo-EM images, directly visualizing the atomic scale parameters and packing arrangements that control the excitonic properties. Our structure clearly shows a brick layer arrangement of the molecules as opposed to the previously thought herringbone arrangement. Furthermore, we identify a new non-biological supramolecular motif – interlocking sulfonates, that may be responsible for the slip-stacked packing and ultimately the J-aggregate nature of LHNs. This motif may be relevant towards other amphiphilic self-assemblies, in general and provides a new chemical handle on predictable self-assemblies.

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Section: Introductionmentioning

confidence: 99%

Near-Atomic Resolution Structure of J-aggregated Helical Light Harvesting Nanotubes

Deshmukh

Zheng

Chuang

et al. 2022

Preprint

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“…Similar to our previous work, we scanned all possible slips excluding the range of 0-2 Å, where H-aggregation predominates. 44 Using the best fit solutions generated in Figure 4b/c, we generated spectra by implementing different amounts of diagonal disorder until we showed agreement with the FWHM of the experimental absorption spectra. The slip value and chiral angle between bundles of 1a and 2a dyes are consistent (24° vs. 30.4° and 6.15 Å vs. 5.5 Å, respectively).…”

Section: Dye Bundlesmentioning

confidence: 96%

“…26 Lattice brick dimensions were determined by adding 2 Å of slip to the Cl-Cl distance across the dye following prior work. 44 Potential tube structures (and thus Hamiltonians) were determined using a planar lattice with a variable slip between bricks. Furthermore, we only considered only chiral angles that permit tubular radii within 1 Å of the measured value.…”

Section: Tablementioning

confidence: 99%

Exploring the Design of Superradiant J-Aggregates from Amphiphilic Monomer Units

Bailey

Deshmukh

Atallah

et al. 2022

Preprint

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Excitonic chromophore aggregates have wide-ranging applicability in fields such as imaging and energy harvesting, however their rational design requires adapting principles of self-assembly to the requirements of excited state coupling. Using the well-studied amphiphilic cyanine dye C8S3 as a template—known to assemble into tubular excitonic aggregates—we synthesize several redshifted variants and study their self-assembly and photophysics. The new pentamethine dyes retain their tubular self-assembly and demonstrate nearly identical bathochromic shifts and lineshapes well into near-infrared wavelengths. However, detailed photophysical analysis finds that the new aggregates show a significant decline in superradiance. Additionally, cryo-TEM reveals that these aggregates readily form short bundles of nanotubes that have nearly half the radii of their trimethine comparators. We employ computational screening to gain intuition on how the structural components of these new aggregates affect their excitonic states, finding that the narrower tubes are able to assemble into a larger number of arrangements, resulting in more disordered aggregates (i.e. less superradiant) with highly similar degrees of redshift.

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“…The methanol solution of TDBC has a relatively low QY of 3%. [42,44] This is because of the flexible trimethine chain, where excited-state C-C rotations act as a major nonradiative recombination pathway reducing the PL QY. [45,46] It has been shown that rigidification of the polymethine chain in many cyanine dyes using fused ring systems leads to a significantly improved PL QY.…”

Section: Characterization Of the Tdbc Molecule And Its Self-assembly ...mentioning

confidence: 99%

Near‐Unity Superradiant Emission from Delocalized Frenkel Excitons in a Two‐Dimensional Supramolecular Assembly

Barotov

Arachchi

Klein

et al. 2022

Advanced Optical Materials

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ordered molecules in a wide variety of morphologies, such as fibers, sheets, and nanotubes. [1,2] Since their independent discovery by Jelley and Scheibe in 1936, [3,4] there has been keen interest in understanding supramolecular assemblies for their unique exciton properties which are distinctly different from those of the single constituting molecules. Close and highly ordered packing allows strong long-range excitonic interaction between the chromophores, resulting in optical properties that strongly depend on the precise alignment of transition dipole moments in the aggregate. In particular, the head-to-tail arrangement of transition dipole moments in J-aggregates leads to the formation of new molecular excitons with redshifted and narrowed spectra. [5] As in natural lightharvesting complexes, molecular excitons in supramolecular assemblies, also called Frenkel excitons, are delocalized over several chromophores in the aggregates. At low temperatures, exciton delocalization lengths of up to 200 molecules have been observed. [6,7] The collective nature of excitations in supramolecular assemblies is responsible for their unique optical properties, such as remarkably narrow and intense absorption, long-range exciton transport, and short radiative lifetimes.As a result of coherent exciton coupling, the oscillator strength for certain excitonic transitions in J-aggregates increases nonlinearly with the number of coupled molecules, leading to strong absorption. In fact, J-aggregates are some of the strongest absorbers known, with measured absorption constants as high as 10 6 cm −1 and absorption strengths reaching 30% at their resonance wavelengths even for a single monolayer. [8,9] Because of their absorption and transport properties, J-aggregates have been widely used as spectral sensitizers in the photographic film industry. [1,2,10] Coherent exciton coupling also leads to a cooperative emission, known as superradiance, which occurs at much faster timescales since the radiative rate is proportional to the oscillator strength. [1,11,12] Even at room temperature, radiative lifetimes as low as 27 ps have been observed for high-quality 2D monolayers of perylene bisimide J-aggregates in the solid state. [9] Because of their strong absorption and superradiant emission, molecular J-aggregates hold great promise towards efficient high-speed light sources, which are important for many applications including high-speed Three general effective strategies are shown to mitigate nonradiative losses in the superradiant emission from supramolecular assemblies. J-aggregates of 5,5′,6,6′-tetrachloro-1,1′-diethyl-3,3′-di(4-sulfobutyl)-benzimidazolocarbocyanine (TDBC) are used to elucidate the nature of nonradiative processes. Selfannealing at room temperature (RT), photo-brightening, and purification of the dye monomers are shown to all lead to substantial increases in emission quantum yields (QYs) and a concomitant lengthening of the emission lifetime, with purification having the largest effect. Structural and optical measuremen...

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Bridging the gap between H- and J-aggregates: Classification and supramolecular tunability for excitonic band structures in two-dimensional molecular aggregates

Cited by 26 publications

References 59 publications

Near-Atomic Resolution Structure of J-aggregated Helical Light Harvesting Nanotubes

Near-Atomic Resolution Structure of J-aggregated Helical Light Harvesting Nanotubes

Exploring the Design of Superradiant J-Aggregates from Amphiphilic Monomer Units

Near‐Unity Superradiant Emission from Delocalized Frenkel Excitons in a Two‐Dimensional Supramolecular Assembly

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