Strukturbestimmung von faserförmigen Gelbildnern mit Röntgenmethoden – Polymorphismus von Cholesterylanthrachinon‐2‐carboxylat

Ostuni, Emanuele; Kamaras, Peter; Weiss, Richard G.

doi:10.1002/ange.19961081213

Cited by 41 publications

(19 citation statements)

References 18 publications

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“…In fact, it is more common for the gel and bulk solid morphs of LMOGs to differ. [68] The presence of a low-angle peak in diffractograms of neat powders and gels whose LMOGs contain long alkyl chains is consistent with lamellar organizations. The Bragg distances (d) of the low-angle peaks, representing the thicknesses of the layers and the calculated van der Waals lengths (l) of the fully extended urea and thiourea molecules [63] are collected in Table 4.…”

Section: Full Papermentioning

confidence: 80%

“…[68] The subtracted diffractograms were then compared with diffraction patterns of the solid LMOGs (Figures 12-14 and Figures S11-S15 in the Supporting Information) to determine whether the molecular packing arrangements in the two are the same. This analysis is possible because the gelator networks of these LMOGs are crystalline in nature; not all LMOG networks are.…”

Section: Full Papermentioning

confidence: 99%

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Urea and Thiourea Derivatives as Low Molecular‐Mass Organogelators

George

Tan

John

et al. 2005

Chemistry A European J

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166

108

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The properties of a series of organogels consisting of a urea or thiourea derivative with one or two n-alkyl substitutuents at the nitrogen atoms (a low molecular-mass organogelator (LMOG)) and an organic liquid are described. They include N,N'-dimethylurea, the LMOG of lowest molecular mass (M(W) 88) we are aware of. The efficiencies of the LMOGs, based the diversity of liquids gelated, the minimum amount required for gelation of a liquid at room temperature, and the temporal and thermal stabilities of the gels formed, have been investigated as a function of the number, length, and substitution pattern of their n-alkyl chains. The gels are thermally reversible and require generally very low concentrations (<2 wt %) of an LMOG. Some of the LMOGs with shorter chains are more efficient than their longer chained analogues. The structural and thermodynamic properties of the gels have been examined by IR, DSC, and X-ray diffraction techniques. Polarizing optical microscopic analyses of the gels show that the nature of gelator aggregates depends mainly on the alkyl chain length. Changes in the aggregation ability have been examined systematically by perturbing the molecular structure.

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Section: Full Papermentioning

confidence: 80%

Section: Full Papermentioning

confidence: 99%

Urea and Thiourea Derivatives as Low Molecular‐Mass Organogelators

George

Tan

John

et al. 2005

Chemistry A European J

Self Cite

166

108

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“…A study of the transition state of the C 6 -O ¥¥¥ H-C 5' IHA reaction gave a similar situation for the glycosidic torsion angles (F À 32.78, Y À 37.38) and a distance of 3.14 ä between the O radical and H-C 5' . [13] In order to substantiate our assumption the C 6 alkoxy radical was generated by reaction of the d-maltose derivative 1 [14] with (diacetoxyiodo)benzene and iodine under irradiation with two 100 W tungsten filament lamps (Scheme 1). The reaction, which proceeds presumably through an alkyl…”

Section: Methodsmentioning

confidence: 85%

Sol–Gel Transcription of Sugar-Appended Porphyrin Assemblies into Fibrous Silica: Unimolecular Stacks versus Helical Bundles as Templates

Tamaru

Takeuchi

Sano

et al. 2002

Angew. Chem. Int. Ed.

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“…Two other conditions should be fulfilled: a low-energy transition state and a distance of around 3 ä between the O radical and the hydrogen atom to be abstracted. [13] In order to substantiate our assumption the C 6 alkoxy radical was generated by reaction of the d-maltose derivative 1 [14] with (diacetoxyiodo)benzene and iodine under irradiation with two 100 W tungsten filament lamps (Scheme 1). A study of the transition state of the C 6 -O ¥¥¥ H-C 5' IHA reaction gave a similar situation for the glycosidic torsion angles (F À 32.78, Y À 37.38) and a distance of 3.14 ä between the O radical and H-C 5' .…”

Section: Methodsmentioning

confidence: 85%

Sol-Gel Transcription of Sugar-Appended Porphyrin Assemblies into Fibrous Silica: Unimolecular Stacks versus Helical Bundles as Templates

Tamaru¹,

Takeuchi²,

Sano³

et al. 2002

Angew. Chem.

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A diverse range of supramolecular structures can be created, not only in nature but also in an artificial system, by self-assembly of designed organic building blocks. In general, the creation of such diverse supramolecular structures seems to be very difficult or nearly impossible in inorganic materials. Is there any innovative method by which ordered supramolecular structures can be created from inorganic materials? The sole method is to transcribe the supramolecular structures of organic molecular assemblies into inorganic materials. It is known that amphiphilic organic molecules are self-assembled into various supramolecular structures, [1] which can be utilized as templates to create novel mesophasic inorganic materials in mesoporous materials, [2] vesicles, [3] ultrathin membranes, [4] etc. [5] As natural examples of these processes, one can prepare inorganic microfibers by mineralization of bacterial fibers [6] or of self-assembled lipid tubules of a galactocerebroside and a phosphate. [7] Since in these attempts it is very important to ™design∫ the different size and shape of the inorganic materials (in the same way that organic compounds and assemblies are ™designed∫), it has been desirable to explore the use of various organic materials as templates and elucidate the mechanism of the template effect. [8] Thus, it is now possible to ™design∫ the inorganic catalysts, electrodevices, etc. at a micrometer level. [9] Increasing attention has been paid to low molecular mass compounds that can efficiently gelate various organic solvents. [10±21] These phenomena are interesting in that the fibrous aggregates formed by noncovalent interactions are responsible for the gelation. We have shown that these ™organic∫ superstructures can be elaborately transcribed into ™inorganic∫ silica materials by utilizing template ± silanol interactions. [22] Recently, we found that an amphiphilic porphyrin (1) bearing four b-d-galactopyranoside groups at its periphery tends to aggregate in a one-dimensional direction, which results in very robust gels in DMF/alcohol mixed solvents. [23,24] Interestingly, we noticed that the speed of bundle growth of this gelator is relatively slow, which would provide us with a greater chance to transcribe nanosized incipient fibers into silica. Here, we report that the sol ± gel transcription of this gel system with tetraethoxysilane (TEOS) results in hollow fiber silica with a 4 ± 5-nm inner diameter, which is comparable to the length of the long axis in 1. This is a rare example of a unimolecular stack immobilized in an inorganic material.Sol ± gel polycondensation of TEOS was carried out using a gel of 1 and DMF/benzyl alcohol (BnOH) according to the method described previously. [22] For example, 1 was dissolved in a mixture of DMF, BnOH, and TEOS at 80 8C. This solution gelled when cooled to room temperature. Before the gel was formed, however, benzylamine (BnNH 2 ) and water were added. In Method A, the mixture was heated at 80 8C again and then left at room temperature for 2 weeks....

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Strukturbestimmung von faserförmigen Gelbildnern mit Röntgenmethoden – Polymorphismus von Cholesterylanthrachinon‐2‐carboxylat

Abstract: Überraschend gut strukturiert sind Gele, die aus faserbildenden Molekülen wie denen der Titelverbindung 1 gebildet werden. Dies ließ sich jetzt anhand von Pulverdiagrammen zeigen und auch, wie sich die Struktur der Gele in Abhängigkeit vom Lösungsmittel ändert.

Cited by 41 publications

References 18 publications

Urea and Thiourea Derivatives as Low Molecular‐Mass Organogelators

Urea and Thiourea Derivatives as Low Molecular‐Mass Organogelators

Sol–Gel Transcription of Sugar-Appended Porphyrin Assemblies into Fibrous Silica: Unimolecular Stacks versus Helical Bundles as Templates

Sol-Gel Transcription of Sugar-Appended Porphyrin Assemblies into Fibrous Silica: Unimolecular Stacks versus Helical Bundles as Templates

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