Applications of microscopy and small angle scattering techniques for the characterisation of supramolecular gels

• Connor R. M. MacDonald and
• Emily R. Draper

Beilstein J. Org. Chem. 2024, 20, 2608–2634, doi:10.3762/bjoc.20.220

• supramolecular gels. Keywords: characterisation; electron microscopy; gelators; small angle scattering; supramolecular materials; Introduction Supramolecular gels are a versatile class of materials, and are of interest in many diverse applications from energy storage to cell culture [1][2]. The versatile

• is the possibility of using different probes in a multicomponent network. Onogi et al. reported one of the first examples of direct imaging, in situ, of self-sorted supramolecular nanofibres [17]. TEM was able to show that the mixture of gelators gave rise to nanofibres with a morphology similar to

• their single-component counterparts. The similarity between these systems made it difficult to assess whether the mixture of gelators resulted in self-sorted or co-assembled fibres using TEM alone. By developing distinct fluorescent probes which could selectively aggregate with, and subsequently stain

The use of isoxazoline and isoxazole scaffolding in the design of novel thiourea and amide liquid-crystalline compounds

• Itamar L. Gonçalves,
• Rafaela R. da Rosa,
• Vera L. Eifler-Lima and
• Aloir A. Merlo

Beilstein J. Org. Chem. 2020, 16, 175–184, doi:10.3762/bjoc.16.20

• study of gels derived from low molecular mass gelators [15][16], and consequently the investigation of gelators of low molar mass with liquid crystal proprieties remains active [17][18]. In addition, isoxazolines and isoxazoles have been identified as promising templates in liquid crystal development

• , they become almost soluble in a hot solution of polar solvents, and when cooled, precipitate into an amorphous solid, limiting their use as gelators. A mesomorphic behavior was observed for thioureas 17a–b, 18a–c and amides 19, 20, 22 and 24. Thiourea 17c and amide 21 did not display mesomorphic

Influence of the cis/trans configuration on the supramolecular aggregation of aryltriazoles

• Sara Tejera,
• Giada Caniglia,
• Rosa L. Dorta,
• Andrea Favero,
• Javier González-Platas and
• Jesús T. Vázquez

Beilstein J. Org. Chem. 2019, 15, 2881–2888, doi:10.3762/bjoc.15.282

• low-molecular-weight gelators have potential applications in high-tech materials [1][2][3] and biomedical sciences [3][4][5][6]. Triazole derivatives have shown excellent gelation properties [7][8][9][10], in addition to a broad range of biological activities [11][12][13][14]. During the synthesis and

Reversible switching of arylazopyrazole within a metal–organic cage

• Anton I. Hanopolskyi,
• Soumen De,
• Michał J. Białek,
• Yael Diskin-Posner,
• Liat Avram,
• Moran Feller and
• Rafal Klajn

Beilstein J. Org. Chem. 2019, 15, 2398–2407, doi:10.3762/bjoc.15.232

• selectivity [35][36][37][38][39][40]. Consequently, arylazopyrazoles have been employed as photoresponsive gelators [41] and adhesives [42] and for controlling antimicrobial response [43][44], cell adhesion to surfaces [45], as well as DNA [46] and microtubule [47] self-assembly using light. Here, we focused

Self-assembly behaviors of perylene- and naphthalene-crown macrocycle conjugates in aqueous medium

• Xin Shen,
• Bo Li,
• Tiezheng Pan,
• Jianfeng Wu,
• Yangxin Wang,
• Jie Shang,
• Yan Ge,
• Lin Jin and
• Zhenhui Qi

Beilstein J. Org. Chem. 2019, 15, 1203–1209, doi:10.3762/bjoc.15.117

• water-soluble crown macrocycle 3 was synthesized according to reported protocols, by using potassium cations as template [86][87]. The primary amine group in 3 offers diverse reaction pathways to design crown ethers appended LMW gelators, dendrimers and polymers [88][89][90][91][92]. In order to

Synthesis and supramolecular self-assembly of glutamic acid-based squaramides

• Juan V. Alegre-Requena,
• Marleen Häring,
• Isaac G. Sonsona,
• Alex Abramov,
• Eugenia Marqués-López,
• Raquel P. Herrera and
• David Díaz Díaz

Beilstein J. Org. Chem. 2018, 14, 2065–2073, doi:10.3762/bjoc.14.180

• describe the preparation and characterization of two new unsymmetrical squaramide-based organogelators. The synthesis of the compounds was carried out by subsequent amine condensations starting from dimethyl squarate. The design of the gelators involved a squaramide core connected on one side to a long

• form gels in some solvents where both gelators 1 and 2 failed. Results and Discussion Synthesis of squaramide-based gelators Squaramides are typically synthesized under mild conditions via aliphatic amine condensation of dialkoxysquarate derivatives [3]. In general, the use of an excess of aliphatic

• hand, solvents such as methylene chloride, chloroform, xylene, benzene and toluene were gelled by 2 but not by 3. Thus, compound 3 can be an alternative to compound 2, and vice versa, depending on the solvent to be gelled (see below). Similarly to other amphiphilic gelators [21][29][31], the formation

Grip on complexity in chemical reaction networks

• Albert S. Y. Wong and
• Wilhelm T. S. Huck

Beilstein J. Org. Chem. 2017, 13, 1486–1497, doi:10.3762/bjoc.13.147

• permission from [75], copyright 2013 American Chemical Society. (c) Self-assembly fibrous structures fueled by molecular gelators. Reprinted with permission from [76], copyright 2010 Wiley-VCH Verlag GmbH & Co. (d) Biocatalytic self-assembly in the presence of chymotrypsin (green) forming hydrogelators that

A new class of organogelators based on triphenylmethyl derivatives of primary alcohols: hydrophobic interactions alone can mediate gelation

• Wangkhem P. Singh and
• Rajkumar S. Singh

Beilstein J. Org. Chem. 2017, 13, 138–149, doi:10.3762/bjoc.13.17

• commonly used protecting group for primary alcohols as a gelling structural component in the design of molecular gelators. We synthesized a small library of triphenylmethyl derivatives of simple primary alcohols and studied their gelation properties in different solvents. Gelation efficiency for some of

• unit which may be further exploited in the design of small molecule based gelators. Keywords: hydrophobic interactions; organogelator; SEM; triphenylmethyl group; xerogel; Introduction Small organic molecules capable of forming gels are called low molecular weight gelators (LMWGs) [1][2][3]. These

• prediction of the gel forming ability of a given molecule is still a formidable challenge, if not altogether impossible [7][8]. Often, the discovery of new gelators relies on an empirical approach wherein structural components capable of forming non-covalent interactions are incorporated into different

My maize and blue brick road to physical organic chemistry in materials

• Anne J. McNeil

Beilstein J. Org. Chem. 2016, 12, 229–238, doi:10.3762/bjoc.12.24

• field of supramolecular chemistry, specifically, and organic materials, broadly. My research group’s efforts toward designing new sensors based on small molecule gelators are described. In particular, I highlight how our design strategy has evolved as we learn more about molecular gelators. This

• are involved, gel formation is reversible and can respond to environmental changes. Understanding which molecules will form gels and under what conditions remains a significant challenge. As a consequence, new gelators are often “discovered” by modifying known gelator scaffolds. Although successful

• , might be gelators. We searched the CSD for molecules containing a mercury atom (Hg2+) that was involved in an intermolecular cation–π interaction [28]. We identified molecule 2a, which exhibited 1D π–cation–π interactions in the solid state (Figure 3). Graduate student Kelsey (King) Carter synthesized

Polythiophene and oligothiophene systems modified by TTF electroactive units for organic electronics

• Alexander L. Kanibolotsky,
• Neil J. Findlay and
• Peter J. Skabara

Beilstein J. Org. Chem. 2015, 11, 1749–1766, doi:10.3762/bjoc.11.191

• design of gelators [33][34]. Combining the exceptional donor strength of TTF and excellent film-forming properties of a conjugated polymer (CP) opens up the possibility to create promising materials with interesting redox behaviour. So far the TTF unit has been used for redox modification of various CP

Synthesis of photoresponsive cholesterol-based azobenzene organogels: dependence on different spacer lengths

• Yuchun Ren,
• Bin Wang and
• Xiuqing Zhang

Beilstein J. Org. Chem. 2015, 11, 1089–1095, doi:10.3762/bjoc.11.122

• ; organogel; photoresponsive; Introduction In the past few decades, low molecular mass organic gelators (LMOGs) have attracted increasing attention not only for basic self-assembly behavior but also for their potential application in areas such as templates [1], light harvesting [2], fluorescent scensing [3

• ], etc. The driving force for the spontaneous formation of gel could be relatively non-covalent interactions such as π–π stacking [4][5][6][7], hydrogen bonding [7][8][9], dipole–dipole [10], and van der Waals interactions [11][12]. A series of cholesterol-based gelators were reported [13][14][15]. These

• can bring about new predictable gelation abilities for the construction of novel cholesterol-based gelators. Azobenzene is one of the smartest molecules among all known photochromic compounds because of its E/Z isomerization [18]. Based on this, photomechanical soft materials containing azobenzene

Synthesis and characterization of pH responsive D-glucosamine based molecular gelators

• Navneet Goyal,
• Hari P. R. Mangunuru,
• Bargav Parikh,
• Sonu Shrestha and
• Guijun Wang

Beilstein J. Org. Chem. 2014, 10, 3111–3121, doi:10.3762/bjoc.10.328

• Navneet Goyal Hari P. R. Mangunuru Bargav Parikh Sonu Shrestha Guijun Wang Department of Chemistry and Biochemistry, Old Dominion University, 4541 Hampton Boulevard, Norfolk, VA 23529, USA 10.3762/bjoc.10.328 Abstract Small molecular gelators are a class of compounds with potential applications

• for soft biomaterials. Low molecular weight hydrogelators are especially useful for exploring biomedical applications. Previously, we found that 4,6-O-benzylidene acetal protected D-glucose and D-glucosamine are well-suited as building blocks for the construction of low molecular weight gelators. To

• better understand the scope of D-glucosamine derivatives as gelators, we synthesized and screened a novel class of N-acetylglucosamine derivatives with a p-methoxybenzylidene acetal protective group. This modification did not exert a negative influence on the gelation. On the contrary, it actually

Triazol-substituted titanocenes by strain-driven 1,3-dipolar cycloadditions

• Andreas Gansäuer,
• Andreas Okkel,
• Lukas Schwach,
• Laura Wagner,
• Anja Selig and
• Aram Prokop

Beilstein J. Org. Chem. 2014, 10, 1630–1637, doi:10.3762/bjoc.10.169

• research as a promising class of cytotoxic compounds [1][2][3][4][5][6][7][8][9][10], as efficient reagents and catalysts [11][12][13][14][15][16], as organometallic gelators [17][18][19][20], and in their own right [21][22]. In order to further investigate and improve these properties it is mandatory to

• with classical organic acylation reactions (Friedel–Crafts reaction, esterification, amide synthesis, Scheme 1). Some of these complexes have been used as organometallic gelators [19][20], as a novel class of cytostatic compounds [26], and catalysts for unusual radical cyclizations [27][28][29][30][31

Charge-transfer interaction mediated organogels from 18β-glycyrrhetinic acid appended pyrene

• Jun Hu,
• Jindan Wu,
• Qian Wang and
• Yong Ju

Beilstein J. Org. Chem. 2013, 9, 2877–2885, doi:10.3762/bjoc.9.324

• ; Introduction The creation of one-dimensional (1D) nanostructures is one of the focused fields in supramolecular chemistry [1][2][3][4]. In order to control the molecular arrangement in 1D structures, low molecular weight gelators (LMWGs) have generated considerable interest during the past decade [5][6]. The

• . As shown in Figure 5, the fiber aggregates can be observed clearly with the red colour which can be attributed to the charge transfer band [53][54]. Chirality study It is known that many chiral gelators can form helical or twisted aggregates upon gelation [55][56]. Even achiral gelators have been

A peptidic hydrogel that may behave as a “Trojan Horse”

• Nicola Castellucci,
• Giorgio Sartor,
• Natalia Calonghi,
• Carola Parolin,
• Giuseppe Falini and
• Claudia Tomasini

Beilstein J. Org. Chem. 2013, 9, 417–424, doi:10.3762/bjoc.9.44

• the cell membrane surface than does the β-sheet conformation [5]. Low-molecular-weight hydrogelators (LMWHGs) are defined as small molecules that self-assemble into long fibers, resulting in the formation of a gel [6][7][8][9][10]. Recently, several examples of peptide or peptidomimetic gelators have

Protonation and deprotonation induced organo/hydrogelation: Bile acid derived gelators containing a basic side chain

• Uday Maitra and
• Arkajyoti Chakrabarty

Beilstein J. Org. Chem. 2011, 7, 304–309, doi:10.3762/bjoc.7.40

• Uday Maitra Arkajyoti Chakrabarty Department of Organic Chemistry, Indian Institute of Science, Bangalore-560012, India 10.3762/bjoc.7.40 Abstract Two bile acid derived molecules containing basic amino groups are reported to be efficient and unusual gelators of organic and aqueous solvents

• gelators 1 and 2 (Scheme 1) having remarkably simple structures with amino groups in the side-chain. Results and Discussion Compound 1 was found to be a super gelator of organic solvents such as 1,2-dichlorobenzene and chlorobenzene and gelled these solvents at very low concentrations (0.05% w/v). In

• gelation and normally cooled gelation phenomenon. The hydrogel consisted of fine fibres and birefringent textures when investigated under a polarizing optical microscope. Finally, these low molecular mass gelators which gel organic and aqueous organic solvents, represent a new class of gelators which have

Synthesis and self-assembly of 1-deoxyglucose derivatives as low molecular weight organogelators

• Guijun Wang,
• Hao Yang,
• Sherwin Cheuk and
• Sherman Coleman

Beilstein J. Org. Chem. 2011, 7, 234–242, doi:10.3762/bjoc.7.31

• Guijun Wang Hao Yang Sherwin Cheuk Sherman Coleman Department of Chemistry, University of New Orleans, New Orleans, LA 70148, Phone: 504 280-1258, Fax: 504 280-6860 Dillard University, 2601 Gentilly Boulevard, New Orleans, Louisiana 70122 10.3762/bjoc.7.31 Abstract Low molecular weight gelators

• are an important class of molecules. The supramolecular gels formed by carbohydrate derived low molecular weight gelators are interesting soft materials that show great potential for many applications. Previously, we have synthesized a series of methyl 4,6-O-benzylidene-α-D-glucopyranoside derivatives

• and found that several of them are good gelators for water, aqueous mixtures of DMSO, or aqueous mixtures of ethanol. The gelation efficiency of these glycolipid derivatives is dependent upon the structures of their acyl chains. In order to understand the influence of the anomeric position of the

Gelation or molecular recognition; is the bis-(α,β-dihydroxy ester)s motif an omnigelator?

• Peter C. Griffiths,
• David W. Knight,
• Ian R. Morgan,
• Amy Ford,
• James Brown,
• Ben Davies,
• Richard K. Heenan,
• Stephen M. King,
• Robert M. Dalgliesh,
• John Tomkinson,
• Stuart Prescott,
• Ralf Schweins and
• Alison Paul

Beilstein J. Org. Chem. 2010, 6, 1079–1088, doi:10.3762/bjoc.6.123

• molecular mass organogelators (LMOGS) is still elusive, although much research attempting to quantify the fundamental aspects of this fascinating phenomenon is underway [1][2][3][4][5]. A wide range of structurally diverse gelators have been identified, and in general, whilst a particular gelator functions

• [35], in which the gelation character was found to depend on both solvent composition and the molecular structure of the gelator. The enthalpy of melting ΔHm for a series of gelators was found to be positive, indicating an endothermic melting process, associated with the increase in entropy

• concentration indicating that the number of scatterers increases, leading to the stiffer gels implied by the concomitant increase in Tgel–sol observed. These gelators form gels in a wide range of solvents, a rather serendipitous and unusual discovery. It is that observation that is elaborated here, and in

Self-assembly and semiconductivity of an oligothiophene supergelator

• Pampa Pratihar,
• Suhrit Ghosh,
• Vladimir Stepanenko,
• Sameer Patwardhan,
• Ferdinand C. Grozema,
• Laurens D. A. Siebbeles and
• Frank Würthner

Beilstein J. Org. Chem. 2010, 6, 1070–1078, doi:10.3762/bjoc.6.122

• versatile gelation and self-assembly properties compared to those of cholesterol-linked PBI gelators reported earlier [10]. We also have demonstrated that the trialkoxybenzamide units provide a unique opportunity to tune the mode of self-assembly (H-type vs. J-type) of PBIs by systematically varying the

• steric crowding in the peripheral alkyl groups [20][21]. These recent findings on PBI gelators prompted us to explore the utility of similar supramolecular design on the self-assembly of other functional π-systems. Herein we describe the synthesis, self-assembly, gelation, and charge-carrier mobility

• gelation concentrations (CGC) were determined for all the solvents gelated with T1 and found to be below 0.3 wt %. This CGC value is much lower compared to those of the previously reported quaterthiophene gelators containing cholesteryl amide peripheral groups [19]. It is interesting to note that in

Expanding the gelation properties of valine-based 3,5-diaminobenzoate organogelators with N-alkylurea functionalities

• Hak-Fun Chow and
• Chin-Ho Cheng

Beilstein J. Org. Chem. 2010, 6, 1015–1021, doi:10.3762/bjoc.6.114

• those of the shorter ones. Keywords: amino acids; hydrophobic effect; organogelators; self-assembly; urea; Introduction Organic gelators are an interesting group of molecules that are able to form a non-covalent three dimensional network with a particular solvent system. The ultimate result is the

Differences between β-Ala and Gly-Gly in the design of amino acids-based hydrogels

• Andreea Pasc,
• Firmin Obounou Akong,
• Sedat Cosgun and
• Christine Gérardin

Beilstein J. Org. Chem. 2010, 6, 973–977, doi:10.3762/bjoc.6.109

• organogels and hydrogels of low molecular weight gelators (LMWG), establishing the relationship between the molecular structure and the gelation mechanism is still a challenge. In this paper our interest focuses on the consequences of slight molecular modifications on the self-assembling behaviour of β-Ala

• molecular weight polymers, physically or chemically cross-linked, but in the recent past, their construction by low molecular weight (LMW) compounds has been explored. With respect to polymeric hydrogels, supramolecular gels of LMWGs (low molecular weight gelators) are assembled by non-covalent forces, such

• solvents, and a hydrophobic domain for van der Waals or hydrophobic interactions (Figure 1). They are able to entrap a large number of solvent molecules per one gelator molecule. Herein the gelators were designed as AA-His-EO2-Alk, bearing i) an hydrophobic alkyl group, ii) a polar peptide group with

Towards racemizable chiral organogelators

• Jian Bin Lin,
• Debarshi Dasgupta,
• Seda Cantekin and
• Albertus P. H. J. Schenning

Beilstein J. Org. Chem. 2010, 6, 960–965, doi:10.3762/bjoc.6.107

• also been reported. In recent years, racemic gel fibers assembled from mixtures of enantiomeric building blocks have been described [11][12][13][14]. In most cases, the racemates were less efficient gelators than the pure enantiomers, and sometimes lead to crystallization [7]. Interestingly, Higashi

Oxalyl retro-peptide gelators. Synthesis, gelation properties and stereochemical effects

• Janja Makarević,
• Milan Jokić,
• Leo Frkanec,
• Vesna Čaplar,
• Nataša Šijaković Vujičić and
• Mladen Žinić

Beilstein J. Org. Chem. 2010, 6, 945–959, doi:10.3762/bjoc.6.106

• -assembly motifs, chirality effects and morphological characteristics of gels formed by chiral retro-dipeptidic gelators in the form of terminal diacids (1a–5a) and their dimethyl ester (1b–5b) and dicarboxamide (1c–5c) derivatives. Terminal free acid retro-dipeptides (S,S)-bis(LeuLeu) 1a, (S,S)-bis(PhgPhg

• racemic and single enantiomer gelators. The heterochiral (S,R)-1c diastereoisomer is capable of immobilizing up to 10 and 4 times larger volumes of dichloromethane/DMSO and toluene/DMSO solvent mixtures compared to homochiral (S,S)-1c. Based on the results of 1H NMR, FTIR, CD investigations, molecular

• characteristics of gels formed by chiral bis(dipeptide)oxalamides. Structurally, such gelators belong to the group of retro-peptides, which have been intensively studied as peptidomimetics due to their higher proteolytic stability and bioavailability compared to natural counterparts [44][45][46][47]. Despite very

Chiral gels derived from secondary ammonium salts of (1R,3S)-(+)-camphoric acid

• Tapas Kumar Adalder,
• N. N. Adarsh,
• Ravish Sankolli and
• Parthasarathi Dastidar

Beilstein J. Org. Chem. 2010, 6, 848–858, doi:10.3762/bjoc.6.100

• form gel. A gel with an organic solvent is called organogel whereas that obtained from water or an aqueous solvent mixture is known as a hydrogel. Among the various classes of supramolecular gelators, interest in low molecular mass organic gelators (LMOGs) [1][2][3][4][5][6][7][8][9][10] is a

• table top rheology, differential scanning calorimetry (DSC), scanning electron microscopy (SEM), single- and powder X-ray diffraction (SXRD and PXRD, respectively). Single crystal structures of two gelators and one nongelator, i.e., DBUAMC 3, DBAMC 6, and DCHADC 1, respectively were determined and

• 1,2-dichlorobenzene xerogels of DBAMC 6, whereas relatively short plate like morphology was observed in the nitrobenzene xerogel of DBUAMC 3. Understandably, the solvent molecules are immobilized in these networks to form gel. To prove structure-property correlation in these gelators, we tried to

Organic gelators and hydrogelators

• Jean-Pierre Desvergne

Beilstein J. Org. Chem. 2010, 6, 846–847, doi:10.3762/bjoc.6.99

• multiple desired functions or properties. In this context, the gelling systems formed by low molecular weight gelators are particularly promising and are the subject of an ever increasing number of studies. A gel consists of one or more gelling agents and a fluid (organic solvent, water, supercritical

• nanoobject conception. Thus, owing to their non-conventional behaviour, low molecular weight gelators are very attractive for applications in various areas, including supramolecular templates or matrices, transport and release of drugs, art conservation, cosmetics, sensors, optoelectronics, actuators, etc

• . However, despite numerous efforts to establish a structure-property relationship for the development of low molecular weight gelling agents, prediction of the gelling ability of a compound is not straightforward. A major challenge today is the rational design of small size molecular gelators coupled with