13205-49-7Relevant articles and documents
Mirror Symmetry Breaking and Network Formation in Achiral Polycatenars with Thioether Tail
Alaasar, Mohamed,Darweesh, Ahmed F.,Cai, Xiaoqian,Liu, Feng,Tschierske, Carsten
, p. 14921 - 14930 (2021/10/14)
Mirror symmetry breaking in systems composed of achiral molecules is of importance for the design of functional materials for technological applications as well as for the understanding of the mechanisms of spontaneous emergence of chirality. Herein, we report the design and molecular self-assembly of two series of rod-like achiral polycatenar molecules derived from a π-conjugated 5,5’-diphenyl-2,2’-bithiophene core with a fork-like triple alkoxylated end and a variable single alkylthio chain at the other end. In both series of liquid crystalline materials, differing in the chain length at the trialkoxylated end, helical self-assembly of the π-conjugated rods in networks occurs, leading to wide temperature ranges (>200 K) of bicontinuous cubic network phases, in some cases being stable even around ambient temperatures. The achiral bicontinuous cubic Ia (Formula presented.) d phase (gyroid) is replaced upon alkylthio chain elongation by a spontaneous mirror symmetry broken bicontinuous cubic phase (I23) and a chiral isotropic liquid phase (Iso1[*]). Further chain elongation results in removing the I23 phase and the re-appearance of the Ia (Formula presented.) d phase with different pitch lengths. In the second series an additional tetragonal phase separates the two cubic phase types.
Hydrogen bonding liquid crystalline benzoic acids with alkylthio groups: Phase transition behavior and insights into the cybotactic nematic phase
Arakawa, Yuki,Sasaki, Yukito,Igawa, Kazunobu,Tsuji, Hideto
, p. 6514 - 6522 (2017/07/17)
A simple but novel class of hydrogen bonding liquid crystalline benzoic acids with alkylthio (or alkylsulfanyl; SR) groups was established. In general, although it is difficult for laterally non-substituted rod-like molecules with an alkylthio group to form some mesophases, the present molecules exclusively form a nematic (N) regime, owing to spontaneous carboxylic dimerization. It was found that the number of carbons in the alkylthio groups strongly correlated with transition temperatures as well as nematogenic stability: odd-even effects. Even-members displayed wider monotropic and enantiotropic N phases, despite the fact that almost all odd-members showed either none or only monotropic-narrower ones. Interestingly, their thermal transition temperatures were lower compared to those for alkoxy (OR) analogues, on account of the small angle (or large bend) of the C-S-C bond as well as the low electron density on their aromatic ring due to the weak electron donor properties of alkylthio groups. Additionally, in-depth wide-angle X-ray diffraction measurements revealed that an alkylthio analogue exhibited significantly enhanced smectic clusters formed in the N regime (or Ncyb phase) as well as the cluster type close to smectic (Sm) A, in comparison with an alkoxy analogue exhibiting a clear SmC-type cluster. The results indicate that a robust S?S intermolecular interaction for an alkylthio group into a mesogen affects the kind of smectic cluster in the Ncyb phase.
The influence of electronic perturbations on the Sulfur-Fluorine Gauche Effect Dedicated to Prof. Dr. Antonio Togni on the occasion of his 60th birthday.
Thiehoff, Christian,Schifferer, Lukas,Daniliuc, Constantin G.,Santschi, Nico,Gilmour, Ryan
supporting information, p. 121 - 126 (2016/01/25)
Herein, a solution phase NMR conformer population analysis is employed to probe the effect of remote electronic perturbations on the conformational equilibria of a series of para-substituted β-fluorosulfides (1), sulfoxides (2) and sulfone derivatives (3). Conformations that allow for stabilizing stereoelectronic (σC-H → σ?C-F) and electrostatic (Fδ-...Sδ+) interactions predominate: this is consistent with the Sulfur-Fluorine Gauche Effect. The molar fractions (χ) of the two possible gauche conformers correlate linearly with the electron-withdrawing aptitude of the para-substituent, rendering the system ideally suited for a Hammett-type analysis. Despite the clear influence that the remote para-substituents have on conformer population, this is superseded by the oxidation state on sulfur (II, IV, VI), where an increased preference for the gauche conformer follows the trend: sulfide sulfone sulfoxide. It is envisaged that this proof of concept in controlling conformer population, either by proximal (oxidation state) or remote tuning (para-substituent), will find application in molecular design.
