Functional liquid-crystalline assemblies: self-organized soft materials.
TL;DR: New approaches to the functionalization of liquid crystals are described and it is shown how the design ofliquid crystals formed by supramolecular assembly and nano-segregation leads to the formation of a variety of new self-organized functional materials.
Abstract: In the 21st century, soft materials will become more important as functional materials because of their dynamic nature. Although soft materials are not as highly durable as hard materials, such as metals, ceramics, and engineering plastics, they can respond well to stimuli and the environment. The introduction of order into soft materials induces new dynamic functions. Liquid crystals are ordered soft materials consisting of self-organized molecules and can potentially be used as new functional materials for electron, ion, or molecular transporting, sensory, catalytic, optical, and bio-active materials. For this functionalization, unconventional materials design is required. Herein, we describe new approaches to the functionalization of liquid crystals and show how the design of liquid crystals formed by supramolecular assembly and nano-segregation leads to the formation of a variety of new self-organized functional materials.
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TL;DR: The new local density functional, called M06-L, is designed to capture the main dependence of the exchange-correlation energy on local spin density, spin density gradient, and spin kinetic energy density, and it is parametrized to satisfy the uniform-electron-gas limit.
Abstract: We present a new local density functional, called M06-L, for main-group and transition element thermochemistry, thermochemical kinetics, and noncovalent interactions. The functional is designed to capture the main dependence of the exchange-correlation energy on local spin density, spin density gradient, and spin kinetic energy density, and it is parametrized to satisfy the uniform-electron-gas limit and to have good performance for both main-group chemistry and transition metal chemistry. The M06-L functional and 14 other functionals have been comparatively assessed against 22 energetic databases. Among the tested functionals, which include the popular B3LYP, BLYP, and BP86 functionals as well as our previous M05 functional, the M06-L functional gives the best overall performance for a combination of main-group thermochemistry, thermochemical kinetics, and organometallic, inorganometallic, biological, and noncovalent interactions. It also does very well for predicting geometries and vibrational frequencies. Because of the computational advantages of local functionals, the present functional should be very useful for many applications in chemistry, especially for simulations on moderate-sized and large systems and when long time scales must be addressed. © 2006 American Institute of Physics. DOI: 10.1063/1.2370993
4,154 citations
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TL;DR: The specific advantages brought up by a design based on the use of the halogen bond will be demonstrated in quite different fields spanning from material sciences to biomolecular recognition and drug design.
Abstract: The halogen bond occurs when there is evidence of a net attractive interaction between an electrophilic region associated with a halogen atom in a molecular entity and a nucleophilic region in another, or the same, molecular entity. In this fairly extensive review, after a brief history of the interaction, we will provide the reader with a snapshot of where the research on the halogen bond is now, and, perhaps, where it is going. The specific advantages brought up by a design based on the use of the halogen bond will be demonstrated in quite different fields spanning from material sciences to biomolecular recognition and drug design.
2,582 citations
TL;DR: This critical review covers various aspects of recent research on discotic liquid crystals, in particular, molecular design concepts, supramolecular structure, processing into ordered thin films and fabrication of electronic devices.
Abstract: Discotic (disc-like) molecules typically comprising a rigid aromatic core and flexible peripheral chains have been attracting growing interest because of their fundamental importance as model systems for the study of charge and energy transport and due to the possibilities of their application in organic electronic devices. This critical review covers various aspects of recent research on discotic liquid crystals, in particular, molecular design concepts, supramolecular structure, processing into ordered thin films and fabrication of electronic devices. The chemical structure of the conjugated core of discotic molecules governs, to a large extent, their intramolecular electronic properties. Variation of the peripheral flexible chains and of the aromatic core is decisive for the tuning of self-assembly in solution and in bulk. Supramolecular organization of discotic molecules can be effectively controlled by the choice of the processing methods. In particular, approaches to obtain suitable macroscopic orientations of columnar superstructures on surfaces, that is, planar uniaxial or homeotropic alignment, are discussed together with appropriate processing techniques. Finally, an overview of charge transport in discotic materials and their application in optoelectronic devices is given (234 references).
1,278 citations
TL;DR: It is likely that nanofabrication will underpin many technologies in the 21st century and the combination of supramolecular chemistry, materials science, and biomedicine allows application-based materials to be developed.
Abstract: It is likely that nanofabrication will underpin many technologies in the 21st century. Synthetic chemistry is a powerful approach to generate molecular structures that are capable of assembling into functional nanoscale architectures. There has been intense interest in self-assembling low-molecular-weight gelators, which has led to a general understanding of gelation based on the self-assembly of molecular-scale building blocks in terms of non-covalent interactions and packing parameters. The gelator molecules generate hierarchical, supramolecular structures that are macroscopically expressed in gel formation. Molecular modification can therefore control nanoscale assembly, a process that ultimately endows specific material function. The combination of supramolecular chemistry, materials science, and biomedicine allows application-based materials to be developed. Regenerative medicine and tissue engineering using molecular gels as nanostructured scaffolds for the regrowth of nerve cells has been demonstrated in vivo, and the prospect of using self-assembled fibers as one-dimensional conductors in gel materials has captured much interest in the field of nanoelectronics.
1,117 citations
TL;DR: This Review will focus on the major classes of columnar mesogens rather than presenting a library of columner liquid crystals, and emphasis will be given to efficient synthetic procedures, and relevant mesomorphic and physical properties.
Abstract: Most associate liquid crystals with their everyday use in laptop computers, mobile phones, digital cameras, and other electronic devices. However, in contrast to their rodlike (calamitic) counterparts, first described in 1907 by Vorlander, disklike (discotic, columnar) liquid crystals, which were discovered in 1977 by Chandrasekhar et al., offer further applications as a result of their orientation in the columnar mesophase, making them ideal candidates for molecular wires in various optical and electronic devices such as photocopiers, laser printers, photovoltaic cells, light-emitting diodes, field-effect transistors, and holographic data storage. Beginning with an overview of the various mesophases and characterization methods, this Review will focus on the major classes of columnar mesogens rather than presenting a library of columnar liquid crystals. Emphasis will be given to efficient synthetic procedures, and relevant mesomorphic and physical properties. Finally, some applications and perspectives in materials science and molecular electronics will be discussed.
1,056 citations
References
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26 May 1995
TL;DR: From molecular to supramolescular chemistry: concepts and language of supramolecular chemistry, molecular recognition, information, complementarity molecular receptors - design principles and more.
Abstract: Part 1 From molecular to supramolecular chemistry: concepts and language of supramolecular chemistry. Part 2 Molecular recognition: recognition, information, complementarity molecular receptors - design principles spherical recognition - cryptates of metal cations tetrahedral recognition by macrotricyclic cryptands recognition of ammonium ions and related substrates binding and recognition of neutral moelcules. Part 3 Anion co-ordination chemistry and the recognition of anionic substrates. Part 4 Coreceptor molecules and multiple recognition: dinuclear and polynuclear metal ion cryptates linear recognition of molecular length by ditopic coreceptors heterotopic coreceptors - cyclophane receptors, amphiphilic receptors, large molecular cage multiple recognition in metalloreceptors supramolecular dynamics. Part 5 Supramolecular reactivity and catalysis: catalysis by reactive macrocyclic cation receptor molecules catalysis by reactive anion receptor molecules catalysis with cyclophane type receptors supramolecular metallo-catalysis cocatalysis - catalysis of synthetic reactions biomolecular and abiotic catalysis. Part 6 Transport processes and carrier design: carrier-mediated transport cation-transport processes - cation carriers anion transport processes - anion carriers coupled transport processes electron-coupled transpoort in a redox gradient proton-coupled transport in a pH gradient light-coupled transport processes transfer via transmembrane channels. Part 7 From supermolecules to polymolecular assemblies: heterogeneous molecular recognition - supramolecular solid materials from endoreceptors to exoreceptors - molecular recognition at surfaces molecular and supramolecular morphogenesis supramolecular heterogeneous catalysis. Part 8 Molecular and supramolecular devices: molecular recognition, information and signals - semiochemistry supramolecular photochemistry - molecular and supramolecular photonic devices light conversion and energy transfer devices photosensitive molecular receptors photoinduced electron transfer in photoactive devices photoinduced reactions in supramolecular species non-linear optical properties of supramolecular species supramolecular effects in photochemical hole burning molecular and supramolecular electronic devices supramolecular electrochemistry electron conducting devices - molecular wires polarized molecular wires - rectifying devices modified and switchable molecular wires molecular magnetic devices molecular and supramolecular ionic devices tubular mesophases. (Part contents).
8,168 citations
Book•
13 Mar 1997
TL;DR: In this paper, the authors discuss the properties of strong and moderate hydrogen bonds in biological molecules and include inclusion of inclusion compounds in the graph set theory of graph set theories, which is used in this paper.
Abstract: 1. Brief History 2. Nature and Properties 3. Strong Hydrogen Bonds 4. Moderate Hydrogen Bonds 5. Weak Hydrogen Bonds 6. Cooperativity, Patterns, Graph Set Theory, Liquid Crystals 7. Disorder, Proton Transfer, Isotope Effect, Ferroelectrics, Transitions 8. Water, Water Dimers, Ices, Hydrates 9. Inclusion Compounds 10. Hydrogen Bonding in Biological Molecules 11. Methods
4,461 citations
TL;DR: A series of hydrophilic and hydrophobic 1-alkyl-3-methylimidazolium room temperature ionic liquids (RTILs) have been prepared and characterized to determine how water content, density, viscosity, surface tension, melting point, and thermal stability are affected by changes in alkyl chain length and anion.
3,469 citations
Book•
01 Jan 2002
TL;DR: The early years of Ionic liquid production were covered in this article, where a new generation of soluble supports for Supported Organic Synthesis (SPOS) was proposed. But this support was not applied to the task-specific Ionic liquids.
Abstract: Preface A Note From The Editors THE EARLY YEARS OF IONIC LIQUIDS SYNTHESIS AND PURIFICATION Synthesis Quality Aspects and other Questions Related to Commercial Ionic Liquid Production Synthesis of Task-specific Ionic Liquids PHYSICO-CHEMICAL PROPERTIES Melting Points Viscosity and Density Solubility and Solvation in Ionic Liquids Gas Solubilities Polarity Electrochemistry STRUCTURE AND DYNAMICS Order in the Liquid State and Structure Computational Modelling of Ionic Liquids Translational Diffusion Molecular Reorientational Dynamics ORGANIC SYNTHESIS Ionic Liquids in Organic Synthesis: Effects on Rate and Selectivity Stoicheiometric Organic Reactions and Acid-catalysed Reactions in Ionic Liquids Transition Metal Catalysis in Ionic Liquids Ionic Liquids in Multiphasic Reactions Task Specific Ionic Liquids (TSILs): A New Generation of Soluble Supports for Supported Organic Synthesis (SPOS) Supported Ionic Liquid Phase Catalysts Multiphasic Catalysis Using Ionic Liquids in Combination with Compressed CO2 INORGANIC SYNTHESIS Directed Inorganic and Organometallic Synthesis Making of Inorganic Materials by Electrochemical Methods Ionic Liquids in Material Synthesis: Functional Nanoparticles and Other Inorganic Nanostructures POLYMER SYNTHESIS IN IONIC LIQUIDS BIOCATALYTIC REACTIONS IN IONIC LIQUIDS INDUSTRIAL APPLICATIONS OF IONIC LIQUIDS CONLUDING REMARKS AND OUTLOOK
3,423 citations
TL;DR: 2-ureido-4-pyrimidone that dimerize strongly in a self-complementary array of four cooperative hydrogen bonds were used as the associating end group in reversible self-assembling polymer systems.
Abstract: Units of 2-ureido-4-pyrimidone that dimerize strongly in a self-complementary array of four cooperative hydrogen bonds were used as the associating end group in reversible self-assembling polymer systems. The unidirectional design of the binding sites prevents uncontrolled multidirectional association or gelation. Linear polymers and reversible networks were formed from monomers with two and three binding sites, respectively. The thermal and environmental control over lifetime and bond strength makes many properties, such as viscosity, chain length, and composition, tunable in a way not accessible to traditional polymers. Hence, polymer networks with thermodynamically controlled architectures can be formed, for use in, for example, coatings and hot melts, where a reversible, strongly temperature-dependent rheology is highly advantageous.
2,011 citations