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

• derivative; organogel; self-assembly; squaramide; supramolecular gel; Introduction Since their discovery, squaramides have gained importance across different fields from chemistry to biomedicine due to their synthetic versatility and wide applicability [1]. These compounds, formed by two amine units

• . In contrast, the spectrum of the xerogel, prepared by freeze-drying the corresponding organogel, revealed a red shift (lower frequency) of the above-mentioned stretching bands compared to solid 3 (C=O Δν ≈5 cm−1; N–H Δν ≈70 cm−1), which is an indication of increased hydrogen-bonding. Characterization

A self-assembled photoresponsive gel consisting of chiral nanofibers

• Lei Zou,
• Dan Han,
• Zhiyi Yuan,
• Dongdong Chang and
• Xiang Ma

Beilstein J. Org. Chem. 2018, 14, 1994–2001, doi:10.3762/bjoc.14.174

• glutamic acid skeleton, containing azobenzene as a photoresponsive group and ureidopyrimidinone (UPy) as a connection site, was designed and synthesized. The monomer is capable of forming an organogel in nonpolar organic solvents and different types of nanostructures in other solvents. The state of the gel

• absorption spectroscopy, circular dichroism, scanning electron microscopy and rheological techniques. This work provides a new method for facile synthesis of chiro-optical gels. Keywords: chirality; nanostructure; organogel; photoresponse; self-assembly; Introduction Supramolecular gels [1][2] immobilized

• allowing the solution to rest at room temperature for 30 min. The gelation ability of compound 3 in various organic solvents was investigated by using the “stable to inversion of a test tube” method (Figure 5a). Here we arrive at the conclusion that compound 3 can only form an organogel in nonpolar

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

• summarized in Table 1. Three of the compounds (TPM-G4, TPM-G5, TPM-G12) formed organogels in polar solvents like dimethylsulfoxide (DMSO), propan-1-ol, propan-2-ol, butan-1-ol, butan-2-ol, diethylene glycol, and triethylene glycol. TPM-G5 (trityl derivative of 1-hexadecanol) formed an organogel in DMSO while

• also monitored. The organogel from TPM-G12 (1% w/v in propan-1-ol and DMSO) remained stable for a long time (more than a month, Figure S4 in Supporting Information File 1) without any appreciable change in its structural integrity. However, on prolonged storage at room temperature, there is a gradual

• derivatives in this study). Hence, the stability of TPM-G12 gel (propan-1-ol) under acidic conditions was tested. Interestingly, acidification of the organogel (by adding 100 µL of 2 N HCl solution to the organogel prepared in 0.5 mL) did not bring about any visible change in its integrity. It remained stable

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

• Yuchun Ren Bin Wang Xiuqing Zhang Chemical Synthesis and Pollution Control Key Laboratory of Sichuan Province of China, China West Normal University, Nanchong 637009, China 10.3762/bjoc.11.122 Abstract A series of azobenzene–cholesterol organogel compounds (M0–M12) with different spacers were

• ; 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

• semicarbazide–azobenzene-based gelators [24]. A new multistimuli photoresponsive organogel containing azobenzene groups was designed and studied by D. Zhu and his co-workers [25]. Q. Zhang synthesized a series of new symmetric dicholesterol-linked gelators [26]. Upon UV–vis irradiation of the gels, a reversible

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

• acids much more readily which results in pH responsive triggered release organogel or hydrogels, provided that the derivatives of compound 3 are effective gelators. Results and Discussion In order to understand the scope of functionalization on monosaccharides and the structure influence of the

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

• 10.3762/bjoc.9.324 Abstract We describe herein the two-component charge-transfer (CT) interaction induced organogel formation with 18β-glycyrrhetinic acid appended pyrene (GA-pyrene, 3) as the donor, and 2,4,7-trinitrofluorenone (TNF, 4) as the acceptor. The use of TNF (4) as a versatile electron acceptor

• properties. UV–vis, fluorescence, mass spectrometric as well as variable-temperature 1H NMR experiments on these gels suggest that the CT interaction is one of the major driving forces for the formation of these organogels. Keywords: charge transfer; glycyrrhetinic acid; organogel; self-assembly

• -component CT interaction induced an organogel formation based on 18β-glycyrrhetinic acid–pyrene conjugate 3 and 2,4,7-trinitrofluorenone (TNF, 4). Their thermal and assembly properties were studied by thermal stability, stoichiometry, scanning electron microscopy (SEM), optical micrographs, and circular

Self-assembly of 2,3-dihydroxycholestane steroids into supramolecular organogels as a soft template for the in-situ generation of silicate nanomaterials

• Valeria C. Edelsztein,
• Andrea S. Mac Cormack,
• Matías Ciarlantini and
• Pablo H. Di Chenna

Beilstein J. Org. Chem. 2013, 9, 1826–1836, doi:10.3762/bjoc.9.213

• conditions, the fibrillar superstructure of the organogel was successfully used as a template for the in-situ sol–gel polymerization of tetraethoxysilane and the further preparation of silica nanotubes. We propose that the driving forces for templating are hydrogen bonding and electrostatic interactions

• between the anionic silicate intermediate species and the self-assembled fibrillar network. Keywords: Hansen parameters; nanotube; organogel; self-assembly; supramolecular gel; Introduction Low molecular mass organogelators (LMOGs) have received increasing attention during the last two decades because

• at 5 °C. The critical concentration for gelation (CCG) was determined by subsequent dilution of the original organogel followed by a heating–cooling process until gel formation was not observed at room temperature (20 °C) The reversible gel–sol transition temperatures (Tg) were measured using the

Enhancement of efficiency in organic photovoltaic devices containing self-complementary hydrogen-bonding domains

• Rohan J. Kumar,
• Jegadesan Subbiah and
• Andrew B. Holmes

Beilstein J. Org. Chem. 2013, 9, 1102–1110, doi:10.3762/bjoc.9.122

• they approached the concentration at which organogel formation occurred. This is a similar effect to that observed for highly crystalline materials [38], for which performance drops rapidly as the crystal domains exceed a certain size. For compound 2, the supramolecular interaction can be quantified in

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

• transition and this time the gel turned pink colour (Figure 3c, heating and cooling reformed the gel). (C) SEM and POM characterization of the gels The gels showed birefringent textures under a polarizing optical microscope [19]. The organogel showed spherulitic structures [20] (where the fibres originated

• from nucleation centres, Figure 4a) and a highly entangled fibrillar network (Figure 4b) at higher (1.25% w/v) and lower (0.25% w/v) concentrations of gelator, respectively. SEM images showed the presence of fine fibres (diameter <1μm) in the organogel (Figure 4c, Figure 4d). However, for the DMSO

• conclusion, we have demonstrated an interesting protonation and deprotonation induced gelation of an organogelator and a hydrogelator, respectively. Using cresol red as an indicator, it was possible to illustrate the acid-stability and base-instability of the organogel and the acid-instability and base

Amphiphilic dendritic peptides: Synthesis and behavior as an organogelator and liquid crystal

• Baoxiang Gao,
• Hongxia Li,
• Defang Xia,
• Sufang Sun and
• Xinwu Ba

Beilstein J. Org. Chem. 2011, 7, 198–203, doi:10.3762/bjoc.7.26

• dendritic polyaspartic acid were designed and synthesized. The organogel and liquid crystal properties of these amphiphilic dendritic peptides were fully studied by field-emission SEM, temperature dependent FT-IR, differential scanning calorimetry, polarization optical microscopy and X-ray diffraction

• experiments. Amphiphilic dendritic peptides G3 show good organogel properties with a minimum gelation concentration as low as 1 wt %. Furthermore, amphiphilic dendritic peptides G3 can form a hexagonal columnar liquid crystal assembly over a wide temperature range. Keywords: amphiphilic; dendritic peptides

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

• electron-rich quaterthiophene derivative with the electron acceptor [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) revealed a nanoscale segregated assembly of the individual building blocks in the blend. Keywords: charge transport; hydrogen bonding; oligothiophene; organogel; self-assembly

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

• transition is associated with gel melting and/or gel formation. When the racemate (R-3 = S-3 = 2.5 mM) was heated and cooled to room temperature, precipitation was observed (Figure 2b). The morphology of the organogel was further characterized by field emission scanning electron microscopy (FESEM) as well as

• organogel in octane at a higher concentration (about 15 mM) also revealed a fibrillar structure, but in this case the fibrils were much bigger in size (nearly 150 nm in diameter) and in some parts they seemed to form two dimensional sheet like lamellar structures (FESEM image, Figure 2d). In order to

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

• characteristics were found to strongly influence both, gelator effectiveness and morphological characteristics of gel aggregates. Keywords: chiral; organogel; oxalamide; retro-peptide; self-assembly; Introduction Reversible processes of peptide, protein and nucleic acids self-assembly are of paramount

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