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

We report on photo-stimulated reversible association and dissociation of hydrogen bonding for self-assembled fibers comprising physical gels. The gels are formed by a hydrogen-bonded gelator contai...

Reversible on-off photo switching of hydrogen bonding for self-assembled fibers comprising physical gels

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Photopatterning of Discotic Liquid-Crystalline Gels

Nematic liquid-crystalline physical gels exhibiting faster responses to electric fields in twisted nematic cells

Some dye molecules self-aggregate to exhibit a lyotropic columnar liquid crystal state (chromonic liquid crystal) via π stacking in relatively highly concentrated aqueous solutions. In this work, the chromonic liquid crystal structure was immobilized, for the first time, with silica networks by way of the sol−gel condensation process. The immobilization of the columnar structure was successfully attained in the presence of 2-(2-aminoethoxy)ethanol, which favorably mediates the interface between the anionic charge of the dye aggregates and the silica network. Without this molecule, the sol−gel process gave rise to a transformation from columnar to lamellar structure. Both spin-coating and dip-coating methods gave essentially the same results. In the dip-coated films, the dye molecules were aligned over a large area with orientation orthogonal to the lifting direction.

Chromonic/Silica nanohybrids: synthesis and macroscopic alignment.

We designed and synthesised new bolaamphiphiles consisting of hydrophobic rigid cores, flexible trisiloxane spacers, and terminal ammonium groups. Organised structures of the bolaamphiphiles with biphenyl and azobenzene cores were examined in the bulk and in the monolayer states. In the bulk states, these molecules exhibited layered liquid crystal phases with an extended molecular conformation. The biphenyl derivative showed only lyotropic liquid crystallinity in the presence of water. In contrast, the azobenzene derivative exhibited both thermotropic and lyotropic liquid crystal behaviour. UV–vis spectroscopy for the materials indicated that the association of the azobenzene cores contributed to the formation of the stable mesomorphic structures. On the other hand, when these molecules were spread on the water surface, monolayer films were formed with both hydrophilic ends on the water surface. The compression of the monolayer films induced the conformational changes in the bolaamphiphiles from a flat-lying extended state to a reverse U-shaped folded state and the core parts were lifted up to the uppermost film surface, maintaining their flat orientation. The cores integrated to the film surface were shown to be monomeric species by UV–vis spectroscopy, whereas the azobenzene cores tend to associate in the bulk and on the water surface at low surface pressures. The trans–cis photoisomerisation and cis–trans thermal isomerisation of the azobenzene cores occurred efficiently in the compressed monolayer films, which is available to tune the surface properties of the monolayer films. For these monolayer films with two-dimensional core arrays, we can expect novel surface-mediated functionalities as photo- and electro-active surfaces, alignment layers for materials synthesis, and molecular sensors due to their tunabilities in core density and polarity.

https://pubs.rsc.org/en/content/articlepdf/2006/SM/B516768J

Organised structures of flexible bolaamphiphiles with trisiloxane spacers: three- and two-dimensional molecular assemblies with different molecular conformation

Norihiro Mizoshita

Papers

Reversible on-off photo switching of hydrogen bonding for self-assembled fibers comprising physical gels

Photopatterning of Discotic Liquid-Crystalline Gels

Nematic liquid-crystalline physical gels exhibiting faster responses to electric fields in twisted nematic cells

Chromonic/Silica nanohybrids: synthesis and macroscopic alignment.

Organised structures of flexible bolaamphiphiles with trisiloxane spacers: three- and two-dimensional molecular assemblies with different molecular conformation