“…However, the presence of open dimers and catemer-like strands, see Fig. 8, stabilises the layered arrangements and hence, strongly promotes smectic phases, 67,68 see Fig. 14.…”
The relationships between liquid crystallinity and hydrogen bonding are studied in mixtures containing 4-pentoxybenzoic acid, 5OBA, and five bipyridines, XBiPy, with spacers having different flexibilities, by Fourier transform infrared spectroscopy.
“…However, the presence of open dimers and catemer-like strands, see Fig. 8, stabilises the layered arrangements and hence, strongly promotes smectic phases, 67,68 see Fig. 14.…”
The relationships between liquid crystallinity and hydrogen bonding are studied in mixtures containing 4-pentoxybenzoic acid, 5OBA, and five bipyridines, XBiPy, with spacers having different flexibilities, by Fourier transform infrared spectroscopy.
“…However, on heating from the crystalline solid a reversible transition to a disordered, or ''soft'' crystal phase (SCr) was seen prior to clearing. In order to first predict virtual mesogenic behaviour for the chiral acid, and also assess the effects of a chiral branch on the liquid crystallinity of supramolecular systems, binary mixtures of the nematogenic non-chiral 4OBA 29,30 and chiral (S)-(2-Me)4OBA were prepared and their thermal behaviour is summarised in Table 2 along with those of the pure acids. For all mixtures containing chiral acid, the chiral nematic phase was seen in place of the conventional nematic, identifiable by its characteristic oily streak texture, shown in Fig.…”
The characterisation of a selection of novel, chiral supramolecular liquid crystals formed by hydrogen-bonding is reported; these are the first examples of the chiral twist-bend nematic phase (N*TB) induced by H-bonding through molecular recognition.
“…Lowering of IR carbonyl stretching absorption frequencies in the solid-state due to strengthened electrostatic interactions as a consequence of crystal packing has been documented (Etter, 1976;Painter et al, 2000). Although keto carbonyl groups and the carboxyl carbonyl groups interact independently of each other and should give two distinct stretching absorption frequencies in the IR spectrum, there appears to be a fortuitous overlap of the two stretching absorption frequencies.…”
The structure of 4,7-dioxononanoic acid previously assigned on the basis of its NMR spectra, was confirmed by X-ray crystallography. The compound exhibits only one sharp peak in its solid state IR spectrum at 1685 cm -1 for its three carbonyl groups. A plausible explanation for this anomaly is provided by X-ray crystallography on the basis of crystal packing and dipole-dipole interactions in aligned arrays of carbonyl groups. This alignment is found in the carboxylic acid group as well, so that the hydrogen bonded interactions of the two carboxylic acid groups found normally in the "dimeric" structures of carboxylic acids in the solid state are not present in the title compound.
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