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

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A new local density functional for main-group thermochemistry, transition metal bonding, thermochemical kinetics, and noncovalent interactions.

About Supramolecular Assemblies of π-Conjugated Systems

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.

The Halogen Bond

In recent years there has been immense interest in studying gels derived from low molecular mass gelators (supramolecular, or simply molecular gels). The motivation for this is not only to understand the fundamental aggregate structures in the gels at different length scales, but also to explore their potential for futuristic technological applications. Gels have been made sensitive to external stimuli like light and chemical entities by incorporating a spectroscopically active or a receptor unit as part of the gelator molecule. This makes them suitable for applications such as sensing and actuating. The diversity of gel structural architectures has allowed them to be utilized as templates to prepare novel inorganic superstructures for possible applications in catalysis and separation. Gels derived from liquid crystals (anisotropy gels) that can act as dynamically functional materials have been prepared, for example, for (re-writable) information recording. Supramolecular gels can be important in controlled release applications, in oil recovery, for gelling cryogenic fuels etc. They can also serve as media for a range of applications. This tutorial review highlights some of the instructive work done by various groups to develop smart and functional gels, and covers a wide spectrum of scientific interest ranging from medicine to materials science.

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Supramolecular gels: Functions and uses

Functional π-Gelators and Their Applications

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.

Functional liquid-crystalline assemblies: self-organized soft materials.

New electroactive supramolecular fibers have been formed by self-assembly of the derivatives of tetrathiafulvalene (TTF) in liquid crystals. These derivatives are designed and prepared by introducing the TTF moiety to the scaffold derived from amino acids such as L-isoleucine whose derivatives function as organogelators. These TTF-based gelators form stable fibrous aggregates in liquid crystals. These fibers are the first example of hydrogen-bonded one-dimensional aggregates having electroactive moieties whose electrical conductivities were measured after doping. Their electronic states have also been characterized by spectroscopic methods. Unidirectionally aligned fibers are formed in the oriented liquid crystal solvents on the rubbed polyimide surface for further functionalization of the fibers.

Electroactive supramolecular self-assembled fibers comprised of doped tetrathiafulvalene-based gelators.

Liquid crystals are molecular materials that combine anisotropy with dynamic nature. Recently, the use of hydrogen bonding for the design of functional liquid crystalline materials has been shown to be a versatile approach toward the control of simple molecularly assembled structures and the induction of dynamic function. A variety of hydrogen-bonded liquid crystals has been prepared by molecular self-assembly processes via hydrogen bond formation. Rod-like and disk-like low-molecular weight complexes and polymers with side-chain, main-chain, network, and guest-host structures have been built by the complexation of complimentary and identical hydrogen-bonded molecules. These materials consist of closed-type hydrogen bondings. Another type of hydrogen-bonded liquid crystals consists of open-type hydrogen bonding. In this case, the introduction of hydrogen bonding moieties, such as hydroxyl groups, induces microphase segregation leading to liquid crystalline molecular order. Moreover, liquid crystalline physical gels have been prepared by the molecular aggregation of hydrogen-bonded molecules in non-hydrogen-bonded liquid crystals. They show significant electrooptical properties. An anisotropic gel is a new type of anisotropic materials forming heterogeneous structures.

Hydrogen-bonded Liquid crystalline materials : Supramolecular polymeric assembly and the induction of dynamic function

Dynamische weiche Materialien werden im 21. Jahrhundert an Bedeutung gewinnen. Zwar sind diese Funktionsmaterialien nicht so bestandig wie Metalle, Keramiken oder Plastik, dafur reagieren sie aber gut auf externe Reize. Geordnete weiche Materialien konnen dynamische Funktionen erfullen. Flussigkristalle aus selbstorganisierten Molekulen sind ein Beispiel hierfur: Sie eignen sich moglicherweise zum Elektronen-, Ionen- oder Stofftransport sowie als sensorisch, katalytisch, optisch oder biologisch aktive Materialien. Um diese Funktionen auszuschopfen, benotigt man unkonventionelle Materialentwurfe. Hier beschreiben wir aktuelle Ansatze zur Funktionalisierung von Flussigkristallen und zeigen, wie das Design von Flussigkristallen durch supramolekulare Aggregation und Nanophasentrennung zu einer Vielfalt selbstorganisierter Funktionsmaterialien fuhrt.

Norihiro Mizoshita

Papers

Functional liquid-crystalline assemblies: self-organized soft materials.

Electroactive supramolecular self-assembled fibers comprised of doped tetrathiafulvalene-based gelators.

Hydrogen-bonded Liquid crystalline materials : Supramolecular polymeric assembly and the induction of dynamic function

Funktionelle flüssigkristalline Aggregate: selbstorganisierte weiche Materialien

Photoresponsive Anisotropic Soft Solids: Liquid‐Crystalline Physical Gels Based on a Chiral Photochromic Gelator