Gramicidin A (gA) is the simplest known natural channel, and important progress in improving conduction activity has previously been obtained with modified natural gAs. However, simple artificial systems mimicking the gA functions are unknown. Here we show that gA can be mimicked using a simple synthetic triazole or 'T-channel' forming compound (TCT), having similar constitutional functions as the natural gAs. As in gA channels, the carbonyl moieties of the TCT, which point toward the T-channel core and surround the transport direction, are solvated by water. The net-dipolar alignment of water molecules along the chiral pore surfaces influences the conduction of protons/ions, envisioned to diffuse along dipolar hydrophilic pathways. Theoretical simulations and experimental assays reveal that the conduction through the T-channel, similar to that in gA, presents proton/water conduction, cation/anion selectivity and large open channel-conductance states. T-channels--associating supramolecular chirality with dipolar water alignment--represent an artificial primitive mimic of gA.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Dipolar water wires stabilize quartets of ureido imidazole compounds (I-quartets) in a manner reminiscent of stabilization of guanine (G) quartets by cation templating (see picture). Detailed facts of importance to specialist readers are published as "Supporting Information". Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Dipolare Wasserdrähte stabilisieren Quartetts von Ureidoimidazolverbindungen (I-Quartetts). M. Barboiu et al. berichten in ihrer Zuschrift auf S. 11 568 ff., dass diese Stabilisierung in einer Weise auftritt, die an die Stabilisierung von Guanin(G)-Quartetts durch Kationentemplate erinnert.

In this review we describe some of most representative examples of metallosupramolecular architectures and dynamic hybrid materials recently published by our group in which supramolecular functional devices are constitutionally self-sorted by crystallization or by sol-gel polymerization. The self-selection is based on constitutional interactions resulting in the dynamic amplification of self-optimized architectures. The dynamic constitutional materials reported here therefore illustrate the convergence of the combinatorial self-sorting of dynamic combinatorial libraries (DCLs) with the specific self-optimized functions, extending the application of constitutional dynamic chemistry 2 from materials science to functional constitutional devices.

We describe a proton exchange membrane (PEM) system in which the self-organization of molecular precursors generates directional proton layers of high ionic group content in a scaffolding hydrophobic hybrid material. In particular, the use of the self-assembling strategy of molecular precursors is noteworthy and we have shown in this paper that it led to self-organized directional proton layers along hundreds of nanometers. The PEM hybrid membranes are homogeneous, flexible and show both thermal and chemical stability. They were surveyed for their ability to form proton layers reaching high ionic conductivities. The simple synthesis procedure and good conductivity/methanol permeability selectivity suggest that the hybrid membranes may be promising candidates for use in DMFCs.

In this paper, we describe the study of the membrane transport properties of mixed supramolecular macrocyclic cation-carriers [1.K](+), [2.Na](+) and phenylureidoarene anion-carriers [3-5.I](-) through bulk liquid membranes. Our efforts involve the evaluation of the transport performances of these systems designed to transport ionic salts Nal and KI and strongly depending on encoded molecular features of the anion-carrier subcomponents.The differences between the transport performances can be attributed to differences between the stability of the complexes [cation-carrier][anion-carrier] in the membrane phase, inversely related to the hydrophilicity of the anion-carrier. In terms of performances, the extraction inside the membrane the transport-rate and the selectivity of K+ are higher than Na+. This indicates that the competitive extraction of [1-K](+) by anion-carriers is more effective and specific than the extraction of [2.Na+].Despite the low rate values obtained for these transport experiments, among all phenylureidoarene anion-carriers the best selectivity is once again thermodynamically optimal for the indole-type (tryptophane-derived) phenylureidoindole compounds (SK+/Na+ = 12.5). (C) 2008 Elsevier B.V. All rights reserved.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

This paper reports on hybrid organic-inorganic dense membrane materials in which protons and ions are envisioned to diffuse along the hydrophilic pathways. The hierarchical generation of functional hybrid materials was realised in two steps. First, the self-assembling properties of 3-(ureidoarene)propyltriethoxysilane compounds 1-5 in aprotic solvents were determined, revealing the formation of supramolecular oligomers. Compounds 1-5 generate organogels in chloroform or in acetone, leading in a second sol-gel transcription step to hybrid membrane materials on a nanoscopic scale. The crystal structures of 1-5 indicate that the arrangement is mainly defined by periodic parallel sheets, resulting from the alignment of hydrophobic organic and inorganic silica layers. Hybrid materials MB 1-MB 4, with a similar lamellar structure, define particularly attractive functional transport devices; they are oriented along the organic layers and sandwiched between the two siloxane layers. These systems have been employed successfully to design solid dense membranes and illustrate how the self-organised hybrid materials perform interesting and potentially useful functions.

The membrane selectivity may be induced either by carrier molecules or by transmembrane channels. From the mechanistic point of view, we use carriers which self-assemble in functional aggregates which would present combined (hybrid) intermediate features between the former carrier-monomers and the resulted channel-forming superstructures. Thus, we therefore studied the membrane transport properties in hybrid dense solid or in mesoporous membranes of such supramolecular organic–inorganic hybrid systems resulted by the dynamic self-assembly of the hydrogen-bonded urea-crown ethers, aromatic aminoacids and nucleosides. This review presents a survey of different methods and processes which can be used for the generation of hybrid supramolecular membranes. Then, basic working principles of molecular recognition-type and self-organized membranes are provided in order to better understand requirements in material design for the generation of functional ionic-conduction pathways. Finally, these systems have been employed successfully to design new dynamic-site complexant membranes immobilized in a mesoporous hybrid nanospace.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

The H-bond mediated self-assembly of hybrid ureido-imidazole compounds has shown that the relative spatial position of the H-bonding groups directs homomeric or heteromeric association of the molecules in the solid state.

We report new hybrid organic-inorganic membrane materials in which alkali cations are envisioned to diffuse along cation-pi aromatic conduction pathways. The hierarchical generation of functional hybrid membrane materials has been realised in two steps. First, the self-assembling properties of 3-(ureidoarene)propyltriethoxysilane compounds in aprotic solvents were determined, revealing the formation of supramolecular oligomers. They led in a second sot-gel transcription step to self-organized hybrid membrane materials at nanoscopic scale. Finally they have been tested in dialysis transport experiments.The transport selectivity through self-organized membranes is due to the interaction of the partially hydrated ions with the hydrophilic or hydrophobic pathways within the matrix of the membrane. This interaction is governed by the energetic balance between the dehydration free energy and the binding energy of cation-pi interaction with the aromatic moieties. (C) 2008 Elsevier B.V. All rights reserved.

The alkoxysilane nucleobase adenine (A) and uracil (U) precursors described in this paper generate in solution a complex library of hydrogen-bonded aggregates, which can be expressed in the solid state as discrete higher oligomers. The different interconverting outputs that nucleobases may form by oligomerization define a dynamic polyfunctional diversity that may be "extracted selectively" in solid state by sol-gel transcription, under the intrinsic stability of the system. After the sol-gel process, unique constitutional preference for specific geometries in hybrid materials is consistent with a preferential arrangement of nucleobase systems, favoring the self-assembly by the Hoogsteen geometry. FTIR and NMR spectroscopy and X-ray powder diffraction experiments demonstrate the formation of self-organized hybrid supramolecular materials. Electron microscopy reveals the micrometric platelike morphology of the hybrid materials. The M(A-U) hybrid material is nanostructured in ordered circular domains of 5 nm in diameter of alternative light and dark rows with an one-dimensional periodicity of 3.5 A.