Role of N–Oxide Moieties in Tuning Supramolecular Gel-State Properties

Ghosh, Dipankar; Björnsson, Ragnar; Damodaran, Krishna K.

doi:10.3390/gels6040041

Cited by 11 publications

(12 citation statements)

References 61 publications

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“…Apart from interactions in and between the gelator molecules, static QM calculations can be used to gain information on the strength and nature of explicit interactions between the gelator and an additive or the solvent [ 40 , 43 ]. In a collaborative effort of the Rai and Kundu groups, a variety of structures of a solvent molecule and a di-Fmoc- L -lysine gelator were optimized at the DFT level of theory [ 44 ].…”

Section: Rationalizing Supramolecular Gelationmentioning

confidence: 99%

Computational Tools to Rationalize and Predict the Self-Assembly Behavior of Supramolecular Gels

Lommel

Borggraeve

Proft

et al. 2021

Gels

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Supramolecular gels form a class of soft materials that has been heavily explored by the chemical community in the past 20 years. While a multitude of experimental techniques has demonstrated its usefulness when characterizing these materials, the potential value of computational techniques has received much less attention. This review aims to provide a complete overview of studies that employ computational tools to obtain a better fundamental understanding of the self-assembly behavior of supramolecular gels or to accelerate their development by means of prediction. As such, we hope to stimulate researchers to consider using computational tools when investigating these intriguing materials. In the concluding remarks, we address future challenges faced by the field and formulate our vision on how computational methods could help overcoming them.

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Section: Rationalizing Supramolecular Gelationmentioning

confidence: 99%

Computational Tools to Rationalize and Predict the Self-Assembly Behavior of Supramolecular Gels

Lommel

Borggraeve

Proft

et al. 2021

Gels

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“…The modification of the pyridyl functionality in pyridyl urea-based compounds could alter the N-H• • • N interactions to N-H• • • O interactions. Recently, we have shown that modifying pyridyl groups to the corresponding pyridyl-N-oxides [30] can restore the N-H• • • O interactions, leading to enhanced gelation ability. In this work, we have selected bis(pyridyl urea)-based compounds (3-HBU [29], 3-BBU [48], 4-HBU, and 4-BBU; see Scheme 1) as the parent compounds.…”

Section: Design and Synthesismentioning

confidence: 99%

“…The presence of pyridyl/pyridyl-N-oxide moieties in our compounds makes them ideal candidates as stimuli-responsive soft materials because these groups are known to interact with the salts/ions. We have previously reported the anion sensing studies of pyridyl-N-oxide compounds [30] and have shown that gel-sol transition can be used to detect cyanide ions [60]. This prompted us to explore the effect of salts in the gelation properties of bis(pyridyl urea) and its corresponding bis(pyridyl-N-oxide urea) compounds.…”

Section: Physical Properties In the Presence Of Saltsmentioning

confidence: 99%

“…The modification of these functional groups will lead to the alteration of specific interactions arising from the particular functional group, which can be considered as an excellent strategy to evaluate the role of specific interactions in gel formation [30,31]. For example, Zinchuan et al have synthesized a cholesterol-based dendrimer gelator from the parent terminal alkyne-based gelator and have shown that the modified compounds formed gel in polar solvents compared to the parent compound, which only formed gel in nonpolar solvents [32].…”

Section: Introductionmentioning

confidence: 99%

“…Compounds with pyridine-N-oxide moieties are an excellent organocatalyst in various racemic and enantioselective reactions and act as oxidant in various oxidation reactions [36]. We have also modified pyridyl mono(urea)-based compounds [25] to pyridyl-N-oxide mono(urea) compounds and showed that the modified compounds formed highly resistant gels towards inorganic salts/ions [30]. We have successfully correlated the solidstate interactions with the gelation properties in mono(urea) LMWGs [30], which prompted us to evaluate the effect of structural modification in bis(pyridyl urea)-based compounds.…”

Section: Introductionmentioning

confidence: 99%

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Making and Breaking of Gels: Stimuli-Responsive Properties of Bis(Pyridyl-N-oxide Urea) Gelators

2021

Self Cite

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The structural modification of existing supramolecular architecture is an efficient strategy to design and synthesize supramolecular gels with tunable and predictable properties. In this work, we have modified bis(pyridyl urea) compounds with different linkers, namely hexylene and butylene, to their corresponding bis(pyridyl-N-oxide urea). The gelation properties of both the parent and the modified compounds were studied, and the results indicated that modification of the 3-pyridyl moieties to the corresponding 3-pyridyl-N-oxides induced hydrogelation. The stability of the parent and modified compounds were evaluated by sol-gel transition temperature (Tgel) and rheological measurements, and single-crystal X-ray diffraction was used to analyze the solid-state interactions of the gelators. The morphologies of the dried gels were analyzed by scanning electron microscopy (SEM), which revealed that the structural modification did not induce any prominent effect on the gel morphology. The stimuli-responsive behavior of these gels in the presence of salts in DMSO/water was evaluated by rheological experiments, which indicated that the modified compounds displayed enhanced gel strength in most cases. However, the gel network collapsed in the presence of the chloride salts of aluminum(III), zinc(II), copper(II), and cadmium(II). The mechanical strength of the parent gels decreased in the presence of salts, indicating that the structural modification resulted in robust gels in most cases. The modified compounds formed gels below minimum gel concentration in the presence of various salts, indicating salt-induced gelation. These results show the making and breaking ability of the gel network in the presence of external stimuli (salts), which explains the potential of using LMWGs based on N-oxide moieties as stimuli-responsive materials.

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Acid⋅⋅⋅Amide Supramolecular Synthon for Tuning Amino Acid‐Based Hydrogels’ Properties

Veronese

Pigliacelli

Bergamaschi

et al. 2023

Chemistry A European J

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Supramolecular hydrogels formed by the self‐assembly of N‐Fmoc‐L‐phenylalanine derivatives are gaining relevance for several applications in the materials and biomedical fields. In the challenging attempt to predict or tune their properties, we selected Fmoc‐pentafluorophenylalanine (1) as a model efficient gelator, and studied its self‐assembly in the presence of benzamide (2), a non‐gelator able to form strong hydrogen bonding with the amino acid carboxylic group. Equimolar mixtures of 1 and 2 in organic solvents afforded a 1:1 co‐crystal thanks to the formation of an acid···amide heterodimeric supramolecular synthon. The same synthon occurred in the transparent gels formed by mixing the two components in 1:1 ratio in aqueous media, as revealed by structural, spectroscopic, and thermal characterizations performed on both the co‐crystal powder and the lyophilized hydrogel. These findings revealed the possibility to modulate the properties of amino acid‐based hydrogels, by involving the gelator in the formation of a co‐crystal. Such crystal engineering‐based approach is demonstrated to be also useful for the time‐delayed release of suitable bioactive molecules, when involved as hydrogel coformers.

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Role of N–Oxide Moieties in Tuning Supramolecular Gel-State Properties

Cited by 11 publications

References 61 publications

Computational Tools to Rationalize and Predict the Self-Assembly Behavior of Supramolecular Gels

Computational Tools to Rationalize and Predict the Self-Assembly Behavior of Supramolecular Gels

Making and Breaking of Gels: Stimuli-Responsive Properties of Bis(Pyridyl-N-oxide Urea) Gelators

Acid⋅⋅⋅Amide Supramolecular Synthon for Tuning Amino Acid‐Based Hydrogels’ Properties

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