How to Distinguish Isodesmic from Cooperative Supramolecular Polymerisation

Smulders, Maarten M. J.; Nieuwenhuizen, Marko M. L.; Greef, Tom F. A. de; Schoot, Paul van der; Schenning, Albertus P. H. J.; Meijer, E. W.

doi:10.1002/chem.200902415

Cited by 493 publications

(525 citation statements)

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“…Assuming an isodesmic mechanism (37,54) in the self-assembly of compound 3a, the apparent association constant at 298 K is on the order of 5 · 10 5 M −1 in a concentration regime of 8 μM to 20 μM. Only a slight decrease to 3 · 10 5 M −1 is observed when switching to a 10-mM PBS buffer at pH 7.4 or a 50-mM succinate buffer at pH 6 (SI Appendix).…”

Section: Resultsmentioning

confidence: 99%

“…Temperature-dependent CD spectra in a 100-mM citrate buffer at pH 6: (A) discotic 1a (5 · 10 −6 M), (B) discotic 2a (2.5 · 10 −6 M) and discotic 3a (20·10 −6 M) and the resulting normalized and fitted CD cooling curves monitored at D λ ¼ 282 nm for discotic 1a, (E) λ ¼ 283 nm for discotic 2a, (F) λ ¼ 269 nm for discotic 3a. The lower three graphs show the normalized data as degree of aggregation Φ n vs. temperature: 0 refers to the molecular dissolved state and 1 to a fully polymerized system; red lines represent the best fits (37,54). Fig.…”

Section: Methodsmentioning

confidence: 99%

“…This is a unique example for directional self-assembly in water whereby the supramolecular polymer shape and size can be dictated by Coulombic interactions. In line with our continuous efforts in elucidating the mechanisms of supramolecular polymerizations (36,37), we have focused on correlating the morphological properties of the produced materials with the appropriate mechanistic details of the self-assembly pathways.…”

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Controlling the growth and shape of chiral supramolecular polymers in water

Besenius

Portale²,

Bomans

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

206

187

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A challenging target in the noncovalent synthesis of nanostructured functional materials is the formation of uniform features that exhibit well-defined properties, e.g., precise control over the aggregate shape, size, and stability. In particular, for aqueousbased one-dimensional supramolecular polymers, this is a daunting task. Here we disclose a strategy based on self-assembling discotic amphiphiles that leads to the control over stack length and shape of ordered, chiral columnar aggregates. By balancing out attractive noncovalent forces within the hydrophobic core of the polymerizing building blocks with electrostatic repulsive interactions on the hydrophilic rim we managed to switch from elongated, rod-like assemblies to small and discrete objects. Intriguingly this rod-tosphere transition is expressed in a loss of cooperativity in the temperature-dependent self-assembly mechanism. The aggregates were characterized using circular dichroism, UV and 1H-NMR spectroscopy, small angle X-ray scattering, and cryotransmission electron microscopy. In analogy to many systems found in biology, mechanistic details of the self-assembly pathways emphasize the importance of cooperativity as a key feature that dictates the physical properties of the produced supramolecular polymers.aqueous self-assembly | controlled architecture | supramolecular polymerization | dynamic materials M olecular self-assembly has emerged as a fascinating area in its own right (1, 2). A toolbox initially developed by supramolecular chemists quickly expanded into an interdisciplinary field aiming at the manipulation of matter at the molecular scale (3, 4). Up until recently self-assembly in dilute aqueous environments has predominantly dealt with linear amphiphiles that form closed structures (5-9), such as spherical micelles, cylindrical or rod-like micelles, and vesicles using, for example, phospholipids (10, 11), synthetic block copolymers (12, 13), or dendrimers (14). Morphological control in objects of defined size or shape, and transitions between different morphologies are increasingly well understood (15)(16)(17)(18). Surprisingly, however, the generality of these concepts has not been translocated into another area of increasing interest, namely, the self-assembly of one-dimensional arrays. In that context the development of discotic monomers has proven to be a valuable route to allow for the synthesis of rod-like supramolecular polymers (19), whose potential applications in functional soft matter include electronics, biomedical engineering, and sensors (20)(21)(22)(23)(24)(25)(26). Considering the enormous interest in such systems, it is surprising that efforts to control the size and shape of nano-and micrometer size one-dimensional objects are rare (27-29); successful strategies rely on the use of templates (30, 31), end cappers (32), or selective solvent techniques (33).In order to control the growth of aqueous one-dimensional supramolecular polymers, we propose to utilize electrostatic repulsive contributions in analogy to surfactant...

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

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Controlling the growth and shape of chiral supramolecular polymers in water

Besenius

Portale²,

Bomans

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

206

187

View full text Add to dashboard Cite

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“…On the other hand, the isodesmic model is governed by a gradual increase in the number of aggregate species with the same energy increment at each addition of monomer. 71,72 To analyze the temperature-dependent data from CD spectra of each metalloporphyrin, both models were applied and the best fits identified the most suitable model in each case ( Figure S3-S4). …”

Section: Self-assembly Of Porphyrins and Metalloporphyrins In Solutionmentioning

confidence: 99%

Bottom-Up Hierarchical Self-Assembly of Chiral Porphyrins through Coordination and Hydrogen Bonds

et al. 2015

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A series of chiral synthetic compounds is reported that show intricate but specific hierarchical assembly because of varying positions of coordination and hydrogen bonds. The evolution of the aggregates (followed by absorption spectroscopy and temperature-dependent circular dichroism studies in solution) reveal the influence of the proportion of stereogenic centers in the side groups connected to the chromophore ring in their optical activity and the important role of pyridyl groups in the self-assembly of these chiral macrocycles. The optical activity spans two orders of magnitude depending on composition and constitution. Two of the aggregates show very high optical activity even though the isolated chromophores barely give a circular dichroism signal. Molecular modeling of the aggregates, starting from the pyridine-zinc(II) porphyrin interaction and working up, and calculation of the circular dichroism signal confirm the origin of this optical activity as the chiral supramolecular organization of the molecules. The aggregates show a broad absorption range, between approximately 390 and 475 nm for the transitions associated with the Soret region alone, that spans wavelengths far more than the isolated chromophore. The supramolecular assemblies of the metalloporphyrins in solution were deposited onto highly oriented pyrolitic graphite in order to study their hierarchy in assembly by atomic force microscopy. Zero and one-dimensional aggregates were observed, and a clear dependence on deposition temperature was shown, indicating that the hierarchical assembly took place largely in solution. Moreover, scanning electron microscopy images of porphyrins and metalloporphyrins precipitated under out-ofequilibrium conditions showed the dependence of the number and position of chiral amide groups in the formation of a fibrillar nanomaterial. The combination of coordination and hydrogen bonding in the complicated assembly of these molecules -where there is a clear hierarchy for zinc(II)-pyridyl interaction followed by hydrogen-bonding between amide groups, and then van der Waals interactions -paves the way for the preparation of molecular materials with multiple chromophore environments.

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“…[8] Detailed studies of their aggregation process have highlighted the cooperative nature of these self-assemblies. [9,10] Derivatives of BTA have been investigated as MRI contrast agents, [11] metal complexation agents [12] and utilized in drug-delivery systems. [13] Investigations of BTA-based self-assemblies have focused on the effects of the aliphatic chains, [14,15] introduction of elements of chirality [16] and substitutions on the central aromatic moiety.…”

Section: Introductionmentioning

confidence: 99%