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Chiral ordered mesoporous silica (COMS) was synthesized in basic media by combining tetraethyl orthosilicate and quaternized aminosilane (with a templating role) silica sources together with four different standard amino acids (arginine, histidine, isoleucine, and proline). Besides the hexagonal MCM-41-type structure, narrow pore size distribution, and high specific surface area, it was found that these solids have potential for enantiomeric separation because of the transference of chirality from the amino acid to the silica. This is illustrated by the resolution of several racemic mixtures (those of proline, isoleucine, trans-4-hydroxyproline, pipecolic acid, valine, leucine, and phenylglycine) with the calcined COMS prepared with l-proline. The opposite behavior observed in induced circular dichroism experiments with calcined COMS, obtained using both enantiomers of proline, confirmed their chiral nature. The high number and variety of existing amino acids, and chiral organic compounds in general, makes these ordered silicas attractive for the production of enantiopure substances.(Figure Presented) © 2011 American Chemical Society., Financial support from the Spanish Ministry of Science and Innovation (MAT2007-61028) is gratefully acknowledged. C.C. also acknowledges a “Juan de la Cierva” grant from the Spanish Science and Innovation Ministry

Bent-core liquid crystals derived from boron coordination compounds have been obtained using a novel approach that incorporates a roof-shaped pyrazabole ring at the core, and lateral wings of different lengths in their aromatic and aliphatic parts. The materials were characterized in solution and in the pure state. Mesophase behavior was studied by polarized light microscopy, differential scanning calorimetry, X-ray scattering, and solid-state NMR. All of the compounds display a nematic mesophase that is not typical of standard nematic phases as a consequence of their bent shape and their transverse dipole moment. The nonstandard behavior was investigated by dielectric spectroscopy and electro-optic studies. Additionally, some compounds display a direct transition from the fluid nematic phase to a crystal-like phase with a very well-defined layer structure. Compounds with extended aromatic structures exhibit additional mesophases, and these were characterized as intercalated smectic mesophases (B6). A nov...

The possibility of achieving chiral helical superstructures in the columnar mesophase of H-bonded complexes of 2,4,6-triarylamino-1,3,5-triazines and chiral benzoic acids is pursued in this work. A series of heterodimeric complexes have been prepared and their mesomorphic states studied by polarized optical microscopy, differential scanning calorimetry, X-ray diffraction, and circular dichroism. It is concluded that steric requirements strongly influence the mesomorphism of these H-bonded complexes. Hence, well-defined columnar arrangements, characterized by high transition enthalpies and a large number of X-ray diffraction rings, are exhibited by complexes with a given number of peripheral tails and a steric compromise between the sizes of the triazine and the acid partners. Optical activity derived from a chiral columnar organization within the mesophase appears for these well-defined hexagonal columnar mesophases.

A wide variety of ionic dendritic macromolecules based on bent-shaped structures have been synthesized and fully characterized. Regular polypropyleneimine dendrimers (PPI) of different generations and a random hyperbranched polymer (PEI) were selected as dendritic cores. Different bent-core structures derived from the 3,4′-biphenyl angular core with 5 or 6 aromatic rings as well as short and long terminal chains and spacers have been used for this study. The bent-core structure acts as strong driving force for the supramolecular arrangement of this type of macromolecules. All of the ionic dendritic polymers prepared show mesogenic behavior over broad temperature ranges, even if the carboxylic acid precursors were not mesomorphous. An extensive chemical structure-supramolecular organization relationship has been proposed for first time for this kind of bent-core dendrimer. Two types of supramolecular packing with lamellar and columnar order have been proposed on the basis of polarizing optical microscopy, differential scanning calorimetry, and X-ray diffraction. Additionally, fibers that present anisotropic optical behavior can be drawn from the materials. These results open new and stimulating possibilities for both bent-core based and dendritic supramolecular systems, with interest in basic and applied supramolecular chemistry and materials science scenarios. © 2011 American Chemical Society., Financial support from the Spanish Government (MICINNFEDER project MAT2009-14636-C03-01, CTQ2009-09030, DGA project E04), and Juan de la Cierva and JAE-DOC (N.G.) programs, and DGA (M.C. and J.V.) fellowship program are gratefully acknowledged.