A new banana-shaped achiral molecule, 1,3-phenylene bis[4-(3-chloro-4-n-octyloxyphenyliminomethyl)benzoate] (PBCOB) has been synthesized, and its ferroelectric properties and homeotropic alignment investigated. The presence of a lateral chloro-substituent in the Schiff 's base moiety prevents the regular stacking of molecules and results in lowering the transition temperature and the degree of crystallinity of the switchable banana phase. Their smectic mesophases, including a switchable banana phase B7, were characterized by differential scanning calorimetry, X-ray scattering and polarizing optical microscopy. Both the left- and right-handed helical domains are spontaneously formed upon cooling from the isotropic liquid to the switchable banana phase B7. By X-ray study, the smectic phases showed a layer spacing of 38.1 Å, compatible with the end-to-end distance of the molecule with a bent conformation. Significantly, the smectic B7 phase exhibited a periodicity of 292 Å that corresponds to a helical structure with periodicity about 7.5 times 38.1 Å. The spontaneous polarization for PBCOB is about 50 nCcm-2 and shows a temperature dependence. The ferroelectric lyomesophase of PBCOB showed a ferroelectric electro-optical switching range extending more than 50°C, switchable at room temperature. 相似文献
Banana-shaped achiral compounds, the 1,3-phenylene bis[4-(alkenyloxyphenyliminomethyl)benzoate]s, were synthesized with varying length of the alkenyl group; their ferroelectric properties are described. The smectic mesophases, including a switchable chiral smectic C (SmC*) phase, were characterized by differential scanning calorimetry, polarizing optical microscopy and the triangular wave method. The presence of vinyl groups at the ends of the linear side-wings in the banana-shaped achiral molecules, containing a Schiff's base mesogen, induced a decrease in melting temperature and formation of the switchable SmC* phase in the melt. The compound having the octenyloxy group exhibited a spontaneous polarization of 120 nC cm?2 on reversal of an applied electric field. 相似文献
Herein, we report a “threading followed by shrinking” approach for the synthesis of rotaxanes by using an “oxygen‐deficient” macrocycle that contained two arylmethyl sulfone units and the dumbbell‐shaped salt bis(3,5‐dimethylbenzyl)ammonium tetrakis(3,5‐trifluoromethylphenyl)borate as the host and guest components, respectively. The extrusion of SO2 from both of the arylmethyl sulfone units of the macrocyclic component in the corresponding [2]pseudorotaxane resulted in a [2]rotaxane that was sufficiently stable to maintain its molecular integrity in CD3SOCD3 at 393 K for at least 5 h. 相似文献
A new method for the synthesis of highly substituted naphthyridine‐based polyheteroaromatic compounds in high yields proceeds through rhodium(III)‐catalyzed multiple C H bond cleavage and C C and C N bond formation in a one‐pot process. Such highly substituted polyheteroaromatic compounds have attracted much attention because of their unique π‐conjugation, which make them suitable materials for organic semiconductors and luminescent materials. Furthermore, a possible mechanism, which involves multiple chelation‐assisted ortho C H activation, alkyne insertion, and reductive elimination, is proposed for this transformation. 相似文献
Mango peels are usually discarded as waste; however, they contain phytochemicals and could provide functional properties to food and promote human health. This study aimed to determine the optimal lactic acid bacteria for fermentation of mango peel and evaluate the effect of mango peel on neuronal protection in Neuron-2A cells against amyloid beta (Aβ) treatment (50 μM). Mango peel can be fermented by different lactic acid bacteria species. Lactobacillus acidophilus (BCRC14079)-fermented mango peel produced the highest concentration of lactic acid bacteria (exceeding 108 CFU/mL). Mango peel and fermented mango peel extracts upregulated brain-derived neurotrophic factor (BDNF) expression for 1.74-fold in Neuron-2A cells. Furthermore, mango peel fermented products attenuated oxidative stress in Aβ-treated neural cells by 27%. Extracts of L. acidophilus (BCRC14079)-fermented mango peel treatment decreased Aβ accumulation and attenuated the increase of subG1 caused by Aβ induction in Neuron-2A cells. In conclusion, L. acidophilus (BCRC14079)-fermented mango peel acts as a novel neuronal protective product by inhibiting oxidative stress and increasing BDNF expression in neural cells. 相似文献
We reported the characteristics of p‐type tin‐oxide (SnO) thin film transistors (TFTs) upon illumination with visible light. Our p‐type TFT device using the SnO film as the active channel layer exhibits high sensitivity toward the blue‐light with a high light/dark read current ratio (Ilight/Idark) of 8.2 × 103 at a very low driven voltage of <3 V. Since sensing of blue‐light radiation is very critical to our eyes, the proposed p‐type SnO TFTs with high sensitivity toward the blue‐light show great potential for future blue‐light detection applications.
Liposomes composed of cell‐penetrating peptide derivatives increased transport across the cell membrane. Conjugating rhodamine to a cell‐penetrating peptide increased the toxicity of rhodamine in E. coli and zebrafish embryos. A similar total protein inhibition pattern with different intensities, indicating that the interaction pathways of the rho‐KTTKS‐CONH2 monomer and liposomes were the same. It suggests that the rho‐KTTKS‐CONH2 liposomes showed higher toxicity because better transport across the cell membrane increased the effective concentration inside cells. The staining of zebrafish embryos using rho‐KTTKS‐CONH2 liposomes showed a longer retention time, suggesting that it can penetrate deeper tissues or organs in zebrafish. 相似文献
Extensive study of the electronic structure of Fe‐NO complexes using a variety of spectroscopic methods was attempted to understand how iron controls the binding and release of nitric oxide. The comparable energy levels of NO π* orbitals and Fe 3d orbitals complicate the bonding interaction within Fe? NO complexes and puzzle the quantitative assignment of NO oxidation state. Enemark–Feltham notation, {Fe(NO)x}n, was devised to circumvent this puzzle. This 40‐year puzzle is revisited using valence‐to‐core X‐ray emission spectroscopy (V2C XES) in combination with computational study. DFT calculation establishes a linear relationship between ΔEσ2s*‐σ2p of NO and its oxidation state. V2C Fe XES study of Fe? NO complexes reveals the ΔEσ2s*‐σ2p of NO derived from NO σ2s*/σ2p→Fe1s transitions and determines NO oxidation state in Fe? NO complexes. Quantitative assignment of NO oxidation state will correlate the feasible redox process of nitric oxide and Fe‐nitrosylation biology. 相似文献