Photo-modulation of supramolecular polymorphism in the self-assembly of a scissor-shaped azobenzene dyad into nanotoroids and fibers

Suda, Natsuki; Saito, Toshihide; Arima, Hironari; Yagai, Shiki

doi:10.1039/d2sc00690a

Cited by 14 publications

(19 citation statements)

References 75 publications

(20 reference statements)

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“…[2][3][4][5][6][7][8] In some cases, the stabilization energy of the different aggregated states differs only by a few kJ mol À 1 , and they can be isolated under specific conditions in the same solvent, giving rise to supramolecular polymorphs. [22][23][24][25][26][27] For example, the formation of distinct 1D (fibrillar) supramolecular polymorphs with different molecular arrangements has been reported for Pt complexes [24] and PBIs [25] as a function of the sample processing (fast/slow heating-cooling process and sonication, respectively). Similarly, lamellar and fibrillar polymorphs have also been reported for squaraines, [28] PBIs, [29] and barbiturates.…”

Section: Introductionmentioning

confidence: 99%

“…[30] However, the interconversion between supramolecular polymorphs is not straightforward, and commonly requires multistep sample processing methods which, in some cases, result in no direct conversion but via intermediate monomeric or kinetic states. [22][23][24][25][26][27][28][29][30] Importantly, since supramolecular polymorphs exhibit different molecular packing, morphology, and/or properties, controlled polymorph transformations are of great interest to develop stimuli-responsive systems. However, direct polymorph transitions are challenging to achieve, particularly in organic solvents where solvophobic effects are attenuated.…”

Section: Introductionmentioning

confidence: 99%

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Thermoreversible Polymorph Transitions in Supramolecular Polymers of Hydrogen‐Bonded Squaramides

et al. 2022

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Hydrogen‐bonded squaramide (SQ) supramolecular polymers exhibit uncommon thermoreversible polymorph transitions between particle‐ and fiber‐like nanostructures. SQs 1–3, with different steric bulk, self‐assemble in solution into particles (AggI) upon cooling to 298 K, and SQs 1 and 2, with only one dendronic group, show a reversible transformation into fibers (AggII) by further decreasing the temperature to 288 K. Nano‐DSC and UV/Vis studies on SQ 1 reveal a concentration‐dependent transition temperature and ΔH for the AggI‐to‐AggII conversion, while the kinetic studies on SQ 2 indicate the on‐pathway nature of the polymorph transition. Spectroscopic and theoretical studies reveal that these transitions are triggered by the molecular reorganization of the SQ units changing from slipped to head‐to‐tail hydrogen bonding patterns. This work unveils the thermodynamic and kinetic aspects of reversible polymorph transitions that are of interest to develop stimuli‐responsive systems.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Thermoreversible Polymorph Transitions in Supramolecular Polymers of Hydrogen‐Bonded Squaramides

et al. 2022

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“…This is due to the high kinetic stability of their circular nanostructures without aggregate termini. 42,57,58 Kinetic Studies on the Stacking of Nanotoroids into Nanotubes. Subsequently, we investigated the hierarchical self-assembly of nanotoroids into nanotubes under isothermal conditions.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…Here, we report the majority-rules-type amplification of molecular asymmetry shown by scissor-shaped azobenzene dyads that hierarchically organize into well-defined toroidal, tubular, and supercoiled nanostructures. Our previous studies using a series of azobenzene dyad analogues − have shown that the hierarchical levels of this system can be accurately controlled by temperature. It has also been shown that the chirality of citronellic-acid-derived side chains, as in 1R and 1S (Figure ), is transferred to supramolecular asymmetry in the different hierarchical levels.…”

Section: Introductionmentioning

confidence: 99%

Amplification of Molecular Asymmetry during the Hierarchical Self-Assembly of Foldable Azobenzene Dyads into Nanotoroids and Nanotubes

2022

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The amplification of molecular asymmetry through self-assembly is a phenomenon that not only comprehends the origin of homochirality in nature but also produces chiroptically active functional materials from molecules with minimal enantiomeric purity. Understanding how molecular asymmetry can be transferred and amplified into higher-order structures in a hierarchical selfassembly system is important but still unexplored. Herein, we present an intriguing example of the amplification of molecular asymmetry in hierarchically self-assembled nanotubes that feature discrete and isolatable toroidal intermediates. The hierarchical self-assembly is initiated via asymmetric intramolecular folding of scissor-shaped azobenzene dyads furnished with chiral side chains. When scalemic mixtures of the enantiomers are dissolved in a non-polar solvent and cooled to 20 °C, single-handed nanotoroids are formed, as confirmed using atomic force microscopy and circular dichroism analyses. A strong majority-rules effect at the nanotoroid level is observed and can be explained by a low mismatch penalty and a high helix-reversal penalty. The single-handed nanotoroids stack upon cooling to 0 °C to exclusively afford their respective single-handed nanotubes. Thus, the same degree of amplification of molecular asymmetry is realized at the nanotube level. The internal packing efficiency of molecules within nanotubes prepared from the pure enantiomers or their scalemic mixtures is likely different, as suggested by the absence of higher-order structure (supercoil) formation in the latter. Xray diffraction analysis of the anisotropically oriented nanotube films revealed looser molecular packing within the scalemic nanotubes, which clearly reflects the lower enantiomeric purity of their internal chiral side chains.

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“…Similarly, lamellar and fibrillar polymorphs have also been reported for squaraines, [28] PBIs, [29] and barbiturates [30] . However, the interconversion between supramolecular polymorphs is not straightforward, and commonly requires multistep sample processing methods which, in some cases, result in no direct conversion but via intermediate monomeric or kinetic states [22–30] …”

Section: Introductionmentioning

confidence: 93%

Thermoreversible Polymorph Transitions in Supramolecular Polymers of Hydrogen‐Bonded Squaramides

et al. 2022

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Photo-modulation of supramolecular polymorphism in the self-assembly of a scissor-shaped azobenzene dyad into nanotoroids and fibers

Abstract: Recent advances in the research field of supramolecularly engineered dye aggregates have enabled the design of simple one-dimensional stacks such as fibers and of closed structures such as nanotoroids (nanorings). More...

Cited by 14 publications

References 75 publications

Thermoreversible Polymorph Transitions in Supramolecular Polymers of Hydrogen‐Bonded Squaramides

Thermoreversible Polymorph Transitions in Supramolecular Polymers of Hydrogen‐Bonded Squaramides

Amplification of Molecular Asymmetry during the Hierarchical Self-Assembly of Foldable Azobenzene Dyads into Nanotoroids and Nanotubes

Thermoreversible Polymorph Transitions in Supramolecular Polymers of Hydrogen‐Bonded Squaramides

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