6 research outputs found
Pairwise Packing of Anthracene Fluorophore: Hydrogen-Bonding-Assisted Dimer Emission in Solid State
Anthracene
derivatives possessing a carbamate group and an ester
group at their 9- and 10-positions, respectively, were prepared to
furnish pairwise packing of anthracene fluorophores in their crystal
structures. They were nonluminescent in ethanol solution and showed
AIE (aggregation-induced emission) in aqueous ethanol solution and
in solid state. Crystal structure analysis of them showed that the
H-bonding networks involved in their crystal structures could be classified
into four patterns, H-bonding between the carbamate and the ester
carbonyl (motif A), H-bonding between the carbamate and the ester
oxygen atom (motif B), H-bonded cyclic dimer of carbamate moieties
(motif C), and H-bonded chain among carbamate moieties (motif D).
Compounds with pairwisely packed anthracene fluorophores showed dimer
emission with the longer fluorescence wavelength than others without
the pair formation. Fluorescence maximum wavelengths and lifetimes
become longer proportional to the degree of overlapping of two facing
anthracene π-planes
Conformation-Directed Hydrogen-Bonding in <i>meta</i>-Substituted Aromatic Ureadicarboxylic Acid: A Conformationally Flexible U‑Shaped Building Block
Crystal
structures of U-shaped aromatic ureadicarboxylic acid possessing two
carboxy moieties at <i>meta</i>-positions of phenyl rings
were investigated. It afforded cocrystals with dipyridyl derivatives.
In addition to the U-shaped conformation obtained by recrystallization
from methanol, another three types of U-shaped conformations were
found in the crystal structure of the cocrystals. The direction of
H-bonding was fixed based on the relative geometry of two carboxy
moieties in the resulting conformations. Depending on these conformations,
triple helices with one-dimensional water channels, infinite cross-belt,
and step-like structures were generated via H-bonding between the
carboxy and the pyridyl moieties. Methanol solvate was obtained for
the cocrystal with 1,4-diÂ(pyridine-4-yl)Âbenzene which showed different
U-shaped conformation of urea dicarboxylic acid from that involved
in the cocrystal free of methanol
Why chiral tartaric imide derivatives give large helical twisting powers in nematic liquid crystal phases: substituent-effect approach to investigate intermolecular interactions between dopant and liquid crystalline molecules
<p>Novel <i>C</i><sub>2</sub>-symmetric chiral dopant derivatives, namely, <i>N</i>-substituted (2<i>R</i>, 3<i>R</i>)-2,3-bis(4-(4-octyloxyphenyl)benzoyloxy)succinimides1<b>a-h</b>, were synthesised, and the effects of the <i>N</i>-substituent and imide-carbonyl groups on the helical twisting powers (HTPs) were investigated in two nematic liquid crystalline compounds, 4-<i>n</i>-pentyl-4ʹ-cyanobiphenyl (5CB) and <i>N</i>-(4-ethoxybenzylidene)-4-<i>n</i>-butylaniline (EBBA). As a result, it was clarified that the bulkiness of the <i>N</i>-substituents has a significant correlation with the HTPs, and the imide-carbonyl group interacts strongly with the cyano group of 5CB to give high HTPs in the nematic phases. However, it is assumed that the imide-carbonyl groups of the dopants do not have strong electrostatic attractive interactions with EBBA molecules in the nematic phase to afford the moderate HTPs.</p
Crystal Structures of S‑Shaped Phenylenediurea Dibenzoic Acids and Their Cocrystals with Melamine: Unusual Zigzag Tape of H‑Bonded Melamine Network
Phenylenediurea
dibenzoic acid derivatives <b>1</b>, <b>2</b>, <b>3</b>, and <b>5</b> and an amide derivative <b>4</b> were
synthesized, and their molecular structures were elucidated
to be an S-shape by single crystal X-ray analysis. Crystals of <b>1</b> were obtained as a DMF solvate, while those of <b>2</b> and <b>3</b> were not. Sheet and ladder structures were created
in the crystal packing of <b>1</b> and <b>3</b>, and <b>2</b>, respectively. Unlike the para-substituted diureas <b>1</b>–<b>3</b> which possessed meso-conformation,
the meta-substituted diurea <b>5</b> exhibited helical-conformation
in its crystal structure. The way of crystal packing of <b>4</b> is analogous to that of the corresponding dicarboxylic acid derivative <b>2</b>. A water cluster of a chair-shaped hexagonal array of water
molecules was created in the crystal structure of <b>4</b>.
Diureas <b>1</b> and <b>2</b> gave cocrystals with melamine
recrystallized from DMF/ethyl acetate and DMF/H<sub>2</sub>O, respectively.
Unusual zigzag tapes of a H-bonding network of melamine were created
in both cocrystals. The zigzag tapes were connected with S-shaped
diureas by H-bonding to furnish an interpenetrated fishnet-type crystal
structure
Piezoluminescence and Liquid Crystallinity of 4,4′-(9,10-Anthracenediyl)bispyridinium Salts
Piezoluminescence
and liquid crystallinity of anthracene-based
bispyridinium salts were investigated in stimulus-responsive luminescent
organic crystals and luminescent ionic liquid crystals. The salts
possess an anthracene moiety as a fluorophore in their center, and
the pyridiniums attached to the anthracene moiety are substituted
with trialkoxybenzyl groups. Single crystals of the salts bearing
two trimethoxybenzyl groups were obtained as solvates. Ethyl acetate,
acetone, and dioxane solvates of the chlorides have almost the same
crystal structures with one-dimensional channels. Grinding of the
solvated crystals caused the extrusion of the included solvent molecules,
which resulted in the red shifts of their fluorescence in the solid
state. The dimethyl sulfoxide solvate of the hexafluorophosphate also
showed piezoluminescene by grinding. TrisÂ(octyloxy)Âbenzyl and trisÂ(dodecyloxy)Âbenzyl
derivatives exhibited rectangular columnar liquid crystals upon being
heated for their bromide and tetrafluoroborate salts and upon being
cooled for their hexafluorophosphate salts. Of these pyridinium salts,
hexafluorophosphates showed characteristic solvent-dependent fluorescence
Simple and Efficient Chiral Dopants to Induce Blue Phases and Their Optical Purity Effects on the Physical Properties of Blue Phases
Blue phases (BPs) have received considerable
attention as light
shutters in the next generation of liquid crystal (LC) displays. However,
no simple and efficient chiral dopant for induction of BPs of commercially
available rodlike LC compounds has been reported. In this study, both
(<i>R</i>) and (<i>S</i>) forms of novel chiral
dopants were synthesized, showed extremely high helical twisting power
values in nematic LC compounds, and induced stable BPs with a small
amount of our chiral dopants (3–5 mol %). In enantiomeric excess
controlled experiments, we found novel phenomena in their physical
properties, such as generation of a metastable chiral nematic phase
between an isotropic state and a BP