Solution‐Phase Structures of Gallium‐Containing Pyrogallol[4]arene Scaffolds

Kumari, Harshita; Kline, S. J.; Wycoff, Wei G.; Paul, Rick L.; Mossine, Andrew V.; Deakyne, Carol A.; Atwood, Jerry L.

doi:10.1002/anie.201200209

Cited by 35 publications

(31 citation statements)

References 30 publications

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“…133 Additionally, the importance of evidence from microscopy techniques cannot be ignored as this provides critical information that can be fed into the SANS data modelling to increase accuracy. 78,79,[81][82][83][84][100][101][102]112,114,115,120,125 In the condensed phase, the combination of multiple techniques can be used to build up detailed pictures, such as those established for P3HT gels and films. [84][85][86][92][93][94][95] The ability to generate such detail is clearly of benefit to the identification of structureproperty relationships and SANS has a crucial role to play, particularly in determining the statistically significant structural parameters.…”

Section: Discussionmentioning

confidence: 99%

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Practical applications of small-angle neutron scattering

Hollamby

2013

Phys. Chem. Chem. Phys.

125

116

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Recent improvements in beam-line accessibility and technology have led to small-angle neutron scattering (SANS) becoming more frequently applied to materials problems. SANS has been used to study the assembly, dispersion, alignment and mixing of nanoscale condensed matter, as well as to characterise the internal structure of organic thin films, porous structures and inclusions within steel.Using time-resolved SANS, growth mechanisms in materials systems and soft matter phase transitions can also be explored. This review is intended for newcomers to SANS as well as experts. Therefore, the basic knowledge required for its use is first summarised. After this introduction, various examples are given of the types of soft and hard matter that have been studied by SANS. The information that can be extracted from the data is highlighted, alongside the methods used to obtain it. In addition to presenting the findings, explanations are provided on how the SANS measurements were optimised, such as the use of contrast variation to highlight specific parts of a structure. Emphasis is placed on the use of complementary techniques to improve data quality (e.g. using other scattering methods) and the accuracy of data analysis (e.g. using microscopy to separately determine shape and size). This is done with a view to providing guidance on how best to design and analyse future SANS measurements on materials not listed below.

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Section: Discussionmentioning

confidence: 99%

“…pyrene) can self-assemble into dimeric or hexameric capsules or hollow cylinders/tubes. [81][82][83] In all cases, SANS was used alongside other techniques (e.g. XRD and NMR) to characterise assembly structures.…”

Section: Amphiphilic Self-assemblymentioning

confidence: 99%

Practical applications of small-angle neutron scattering

Hollamby

2013

Phys. Chem. Chem. Phys.

125

116

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“…SAS results offer a bulk average over an appreciable volume, are dominated by the most commonly existing assembly structure, and therefore have a high statistical relevancy. SAXS and SANS are routinely used to probe various supramolecular assemblies, including molecular capsules and tubes, [10,11] micelles, [2,3,12,13] vesicles, [14,15] organogels, [2,16] and protein tertiary structures. [17] Combining SAXS and SANS can be particularly insightful.…”

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confidence: 99%

“…[3] A similar model without shell, has previously been used to model SANS data from toroidal charged block copolymer micelles, [23] with others using hollow cylinders to approximate the toroidal structure. [10] The dimensions observed by AFM were used as starting estimates for model fitting, and the scattering length densities of core, shell and solvent were estimated and fixed (see SI). SANS and SAXS data were fitted simultaneously using the multiple dataset fitting capability of the SASfit software [24] to yield the dimensions R (toroid radius), a (cross-section core radius), δshell (shell width), b (cross-section aspect ratio) and the S(Q) parameters.…”

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confidence: 99%

Simultaneous SAXS and SANS Analysis for the Detection of Toroidal Supramolecular Polymers Composed of Noncovalent Supermacrocycles in Solution

et al. 2016

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Molecular self-assembly primarily occurs in solution. To better understand this process, techniques capable of probing the solvated state are consequently required. Small-angle scattering (SAS) has a proven ability to detect and characterise solutions, but is rarely applied to more complex assembly shapes. Here, we apply small-angle X-ray and neutron scattering to observe toroidal assemblies in solution. Combined analysis confirms that the toroids have a core-shell structure, with a π-conjugated core and an alkyl shell into which solvent penetrates. The dimensions determined by SAS agree well with those obtained by (dried-state) atomic force microscopy. Increasing the number of naphthalene units in the molecular building block yields greater rigidity, as evidenced by a larger toroid and a reduction in solvent penetration into the shell. The detailed structural analysis demonstrates the applicability of SAS to monitor complex solution-based self-assembly.Self-assembly processes range from the micellisation of amphiphiles [1][2][3] to supramolecular polymerization [4] and onwards to the more elaborate folding of DNA origami.[5] When apolar molecules associate, solvent-solvent and solvent-solute interactions play a key role in the assembly process.[6] Upon solvent removal, the assembly structure is rarely unaffected, necessitating the probing of the sample structure in solution in order to form an accurate assembly model. Unfortunately, this is often difficult to do, and, while cryo-electron microscopy can reveal high-resolution structures in (frozen) solution, [1,7] there are only a few reports of its use in non-aqueous solutions.[2]Conversely, small-angle scattering (SAS) techniques using Xrays (SAXS) [8] or neutrons (SANS) [9] can detect molecular assemblies with dimensions typically between 1-100 nm in solution. SAS results offer a bulk average over an appreciable volume, are dominated by the most commonly existing assembly structure, and therefore have a high statistical relevancy. SAXS and SANS are routinely used to probe various supramolecular assemblies, including molecular capsules and tubes, [10,11] micelles, [2,3,12,13] vesicles, [14,15] organogels, [2,16] and protein tertiary structures.[17] Combining SAXS and SANS can be particularly insightful. The SAXS signal arises from regions contrasting in electron density, while SANS (in this case) highlights 1 H-rich regions of an assembly dispersed in a 2 D-rich solvent.[9]Therefore, for molecules comprising both π-conjugated (e − -rich, 1 H-poor) and aliphatic ( 1 H-rich, e − -poor) parts such as asphaltenes [18] or alkyl-fullerene derivatives, [2] the SAXS and SANS signals will derive from the π-conjugated-rich and aliphatic-rich parts of an assembly, respectively. In these cases, combined SAXS and SANS allows the detection not only of a particular assembly morphology in solution but also of the internal structure. In this regard, the unique self-assembly of 1 in apolar media is an attractive target for SAS investigations ( Figure 1a). Molecule 1, ...

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“…[8a,b] Resorcin[4]arene hexamers accommodate amuch larger range of guests than pyrogallol-[4]arene hexamers do [8] and several examples of catalysis within the resorcin[4]arene hexamers have been reported. [13] Schalley and co-workers also studied these hexameric capsules in the gas phase. [10] Thei nformation gathered to date on the hexameric capsules of systems 1 and 2 was obtained in the solid-state by X-ray crystallography [11] or in solution by NMR, diffusion NMR, [12] and small-angle neutron scattering.…”

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confidence: 99%

Hexameric Capsules Studied by Magic Angle Spinning Solid‐State NMR Spectroscopy: Identifying Solvent Molecules in Pyrogallol[4]arene Capsules

2015

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Powders of pyrogallol[4]arene hexamers were produced by evaporation from organic solvents and were studied, for the first time, by magic angle spinning solid-state NMR (MAS ssNMR). Evaporation selectively removed non-encapsulated solvent molecules leaving stable hexameric capsules encapsulating solvent molecules. After exposure of the powder to solvent vapors, (1)H/(13)C heteronuclear correlation MAS ssNMR experiments were used to assign the signals of the external and encapsulated solvent molecules. The formed capsules were stable for months and the process of solvent encapsulation was reversible. According to the ssNMR experiments, the encapsulated solvent molecules occupy different sites and those sites differ in their mobility. The presented approach paves the way for studying guest exchange, guest affinity, and gas storage in hexamers of this type in the solid state.

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Solution‐Phase Structures of Gallium‐Containing Pyrogallol[4]arene Scaffolds

Cited by 35 publications

References 30 publications

Practical applications of small-angle neutron scattering

Practical applications of small-angle neutron scattering

Simultaneous SAXS and SANS Analysis for the Detection of Toroidal Supramolecular Polymers Composed of Noncovalent Supermacrocycles in Solution

Hexameric Capsules Studied by Magic Angle Spinning Solid‐State NMR Spectroscopy: Identifying Solvent Molecules in Pyrogallol[4]arene Capsules

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