| Apr 20, 2026 |
Folding-mediated self-assembly of luminescent molecules reveals a new design principle for efficient light-energy transport
(Nanowerk News) In biological systems, especially for protein molecules, the formation of nanotubular structures is often guided by molecular folding. The folding process organizes interaction sites and enables the formation of complex architectures with high structural precision. However, translating that principle to synthetic small-molecule systems has remained challenging.
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In a recent study, a team of scientists led by Professor Shiki Yagai from the Graduate School of Engineering, Chiba University, Japan, reported that π-luminophore dyads can overcome this limitation and assemble into well-defined supramolecular nanotubes with unusual excitonic properties.
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Their research findings were published in the Journal of the American Chemical Society (“Folding-Mediated Self-Assembly of Sterically Demanding π-Luminophore Dyads into Nanotubes Exhibiting Multidirectional Exciton Transport”).
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| Sterically demanding diphenylanthracene-based artificial π-luminophores can be programmed to self-fold and preorganize into highly ordered supramolecular nanotubes. This folding-mediated assembly guides directional π–π stacking and cooperative interactions, enabling the formation of stable curved architectures. Notably, the resulting nanotubes exhibit multidirectional exciton migration—both along the tube axis and around its circumference—revealing a new molecular design strategy for advanced optoelectronic materials. (Image: Professor Shiki Yagai, Chiba University)
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“Diphenylanthracene (DPA) derivatives are sterically demanding and were previously considered to be aggregation-incompetent. We wanted to see if they can be programmed to form highly ordered supramolecular nanotubes through folding-mediated self-assembly,” mentioned Prof. Yagai.
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The team synthesized a series of artificial molecules capable of adopting folded conformations. The central aromatic unit was systematically expanded from terphenylene to diphenylnaphthalene and finally to DPA. They examined how these structural variations influenced molecular folding, as well as the resulting assembly structures and properties. X-ray and neutron scattering techniques were used to analyze how folded molecules assemble into nanotubes, while polarized UV–vis and infrared spectroscopy provided detailed insights into their internal organization.
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The study showed that the terphenylene-based system formed twisted ribbon-like structures, the diphenylnaphthalene derivative generated curved assemblies including helical coils and toroids, and the DPA analog produced hollow cylindrical nanotubes. The researchers attributed this structural progression to folding-assisted directional π–π stacking combined with cooperative hydrogen bonding. These together directed the curved supramolecular assembly, enabling the emergence of complex nanotubular structures. The study also confirmed that in concentrated solutions, the nanotubes can be arranged to form luminescent fibers that reach several centimeters in length.
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Molecular simulation results showed that a stable nanotube is achieved when DPA units adopt alternating tilts within stacked toroidal layers. This arrangement generates a herringbone-like chromophore wall, relieving stacking frustration and stabilizing the curved tubular architecture. The alternating molecular tilt thus proves to be a key structural principle underlying nanotube stability.
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The research team also investigated energy transfer within these spontaneously assembled, intricate tubes. While it was previously known that energy is transferred along the length of such tubular structures, directional energy transfer has not been well evaluated. In this case, the nanotubes displayed multidirectional exciton migration.
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Unlike many one-dimensional supramolecular assemblies, where energy transport is mainly expected along the longitudinal axis, these nanotubes enabled exciton motion both along the tube axis and around its circumference. Time-resolved fluorescence anisotropy measurements indicated exciton migration lengths of about 55 nm in the axial direction and about 11 nm circumferentially. This behavior links supramolecular topology directly to energy-transport function and suggests that closed tubular chromophore packing can support more complex excitonic dynamics than conventional linear stacks.
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This study revealed a fundamental design principle for constructing curved microstructures, such as rings, helices, and tubes, that have been difficult to achieve by conventional approaches. This can be achieved by controlling the interaction sites and orientations during molecular assembly through folding.
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Molecular design based on such folding is expected to provide new guidelines for creating artificial nanostructures that mimic the sophisticated organization seen in proteins. The nanotubes obtained in this work exhibited three-dimensional energy transport within their interiors. “Molecular assemblies with such energy-transfer capabilities can be developed for applications in organic materials that utilize light energy, including artificial photosynthesis and highly efficient luminescent systems,” concluded Prof. Yagai.
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