X-Ray Diffraction from Mesophases of Some Stilbazole Complexes of Silver(I); Monodomain Determination of a Thermotropic Cubic Phase

Abstract

A family of mesomorphic bis(alkoxystilbazole) silver(I) dodecylsulphate and octylsulphate complexes has been studied by X-ray scattering in their various mesophases. In particular, many of the complexes exhibit a thermotropic cubic mesophase and, for one example, a monodomain was obtained allowing the space group to be unequivocally identified. A model for the formation of these cubic phases is proposed

Rational Tuning of Melting Entropies for Designing Luminescent Lanthanide‐Containing Thermotropic Liquid Crystals at Room Temperature

“…[29] Since there are six alkyl chains occupying the molecular area on each part of the molecule in the layered organization (Figure 5a), we eventually obtain a m = 148/6 = 24.7 2 as the cross-sectional area of each chain, a value in good agreement with a m = 22-25 2 expected for a SmA organization. [29] However, we cannot completely exclude an alternative hexagonal columnar arrangement Col h for the tabular ligand L11, in which the two diffraction peaks detected at 36.1 and 18.0 would correspond to the reflection (hk) = (10) and (20) with squared spacing ratios 1/d 2 hk / h 2 + k 2 + hk = 1 and 4, respectively, whereas the intensity of (hk) = (11) with d !I, a = 41.1 ), [18] the perpendicular connection of six additional dodecyloxy chains in L11 does not drastically increase the size of the cross section of the column, but it transforms a glassy melting transition into a first-order melting transition, for which DH m and DS m are easily obtained by DSC. The latter observation merits some comments.…”

“…PLM observations display a noncharacteristic and poorly developed birefringent texture in the À30 to 130 8C domain (see Figure S10b in the Supporting Information), but SA-XRD patterns unambiguously show up to seven reflections with squared spacing ratios 1/d 2 hk / h 2 + k 2 + hk = 1, 3, 4, 7, 9, is the estimated density of the mesophase at the temperature, T). [29] [c] No SA-XRD data recorded for this complex.…”

“…[29] The mathematical analysis leads to an intercolumnar separation a = 37.7 associated with a cross-sectional area of the rigid core amounting to S = ( ffiffi ffi 3 p /2)·a 2 = 1233 2 (Table S5 in at 25 8C in the hexagonal columnar mesophase, [29] we calculate a molecular volume V mol = 6041.5 3 for the asymmetric monomeric unit, and thus a periodicity of h = Z V mol /S = 4.90 for a mononuclear disk-like unit along the column. 3 ] 2 (37.7 ) implies interdigitation between the molten dodecyloxy chains, because a single twelve-carbon unit chain in all-trans conformation extends to approximately 15 .…”

Recent Progress in the Synthesis and Structural Clarification of Thermotropic Cubic Phases

“… Phase diagrams of three rod‐shaped molecules as a function of alkyl chain length ( n , number of carbon atoms in the chain) and temperature. a) Compound 1 with XNO 2 ,10e,g b) compound 3 ,11d,f and c) compound 5 with one chain at each terminal 13a,b. Transition temperatures were determined by differential scanning calorimetry on heating.…”

T‐Shaped Ionic Liquid Crystals Based on the Imidazolium Motif: Exploring Substitution of the C‐2 Imidazolium Carbon Atom

“…[70,71] Usually, rodlike and polycatenar mesogens tend to exhibit bicontinuous (or tricontinuous [72] ) thermotropic Cub phases of Im3 m or Ia3 d symmetry. [51,70,[73][74][75][76][77][78] Therefore, the observation of a Cub phase of Pm3 m symmetry for compound 8 merits further investigation. Direct Fourier reconstruction of the electron density profile on the basis of the observed small-angle Xray scattering (SAXS) intensities might be difficult because the (211) reflection is too dominating.…”