An Above-Room-Temperature Molecular Ferroelectric: [Cyclopentylammonium]2CdBr4.

Molecular ferroelectrics as alternatives to the conventional inorganic ferroelectrics have been greatly developed in past decades; many of these have been discovered and designed through various chemical means due to their structural adjustability. However, it is still a huge challenge to obtain high (above room temperature) Curie temperature (Tc) molecular ferroelectrics to meet the application requirements. Here, we present a new organic-inorganic hybrid molecular ferroelectric, [cyclopentylammonium]2CdBr4 (1), showing a moderate above-room-temperature Tc of 340.3 K. The mechanism of the ferroelectric phase transition from Pnam to Pna21 in 1 is ascribed to the order-disorder transition of both the organic cations and inorganic anions, affording a spontaneous polarization of 0.57 µC/cm2 for the ferroelectric phase. Using piezoresponse force microscopy (PFM), we clearly observed the antiparallel 180° stripe domains and realized the polarization switching, unambiguously establishing the existence of room-temperature ferroelectricity in the thin film. These attributes make it attractive for use in flexible devices, soft robotics, biomedical devices, and other applications.

Antioxidant and Anticancer Activities of Essential Oil from Gannan Navel Orange Peel.

China is one of the leading producers of citrus in the world. Gannan in Jiangxi Province is the top navel orange producing area in China. In the present study, an essential oil was prepared by cold pressing of Gannan navel orange peel followed by molecular distillation. Its chemical composition was analyzed by GC-MS. Twenty four constituents were identified, representing 97.9% of the total oil. The predominant constituent was limonene (74.6%). The anticancer activities of this orange essential oil, as well as some of its major constituents, were investigated by MTT assay. This essential oil showed a positive effect on the inhibition of the proliferation of a human lung cancer cell line A549 and prostate cancer cell line 22RV-1. Some of the oil constituents displayed high anticancer potential and deserve further study.

Self-assembled metallogels formed from N,N',N''-tris(4-pyridyl)trimesic amide in aqueous solution induced by Fe(III)/Fe(II) ions.

In this work, we report self-assembled metallogels formed from a ligand of trimesic amide, N,N',N''-tris(4-pyridyl)trimesic amide (TPTA), induced by Fe(III)/Fe(II) ions. TPTA is difficult to dissolve in water even in the presence of some metal ions such as Cu(2+), Co(2+), Ni(2+), K(+), Na(+) and Mg(2+) under heating, and it exhibits no gelation ability. Interestingly, upon heating TPTA can be dissolved easily in aqueous solution containing Fe(3+)/Fe(2+), and subsequently self-assembled into metallogels after cooling. The metallogels could also be formed in aqueous solutions of mixed metal ions containing Fe(3+)/Fe(2+), indicating that the other metal ions do not affect the formation of Fe(III)-TPTA and Fe(II)-TPTA metallogels. The high selectivity of metallogel formation to Fe(3+)/Fe(2+) may be used for application in the test of Fe(3+)/Fe(2+). The metallogels obtained are characterized by scanning electron microscopy, Fourier transform infrared spectra, nuclear magnetic resonance spectra, rheological measurements and scanning tunneling microscopy. The results indicate that TPTA can self-assemble into fibrous aggregates in Fe(3+)/Fe(2+) aqueous solution through the metal-ligand interactions and intermolecular hydrogen bonding. This kind of metallogel also possesses good mechanical properties and thermoreversibility.

Heat-set gels formed from easily accessible gelators of a succinamic acid derivative (SAD) and a primary alkyl amine (R-NH2).

Currently, the design and construction of an intelligent stimuli-responsive gel system is still a significant challenge. We present here a new gel system from which the formation of heat-set gels, conventional gels and irreversible heat-set gels can be achieved in aromatic solvents. This gel system is based on two-component gelators containing a succinamic acid derivative (SAD) and a primary alkyl amine (R-NH2). With the increase of temperature to 85 °C, a rarely reported reversible heat-set gel (gel formation with the increase of temperature) is afforded. Upon addition of fatty acids into two-component gelators, a conventional gel (gel formation with the decrease of temperature) is formed. When the fatty acid is replaced with dicarboxylic acid, a new heat-set gel is generated, which is irreversible and thermally super-stable. X-ray diffraction analysis reveals that the formation of a reversible heat-set gel relies on electrostatic interactions, hydrogen bonds, and hydrophobic interactions. These two-component gelators show a perfect gel system for the formation of diverse gels including heat-set gels, conventional gels and irreversible heat-set gels. The tunable strategy demonstrated in this letter may provide a new way for creation of more functional gels in gel science.

Uncovering the Role of Metal Catalysis in Tetrazole Formation by an In Situ Cycloaddition Reaction: An Experimental Approach.

Using an experimental approach, the role of metal catalysis has been investigated in the in situ cycloaddition reaction of nitrile with azide to form tetrazoles. It has been shown that metal catalysis serves to activate the cyano group in the nitrile reagent by a coordinative interaction.

Rhodium(III)-Catalyzed Switchable ß-C(sp2)-H Alkenylation and Alkylation of Acyclic Enamides with Allyl Alcohols.

Herein, rhodium(III)-catalyzed ß-C(sp2)-H alkenylation and alkylation of enamides are presented using readily accessible allylic alcohols by switching the reaction conditions. This tunable transformation has been applied to a wide range of substrates and typically proceeded with excellent regioselectivity and stereoselectivity as well as with good functional group tolerance. The catalytic system offers an efficient approach for synthesizing various functionalized enamides bearing N-(2Z,4E)-butadiene and (Z)-ß-C(sp2)-H alkylated enamides. In addition, mechanistic experiments suggest that Rh(III)-catalyzed C-H activation is not related to the critical step.

A microporous hydrogen-bonded organic framework: exceptional stability and highly selective adsorption of gas and liquid.

An extremely stable hydrogen-bonded organic framework, HOF-8, was fabricated. HOF-8 is not only thermally stable but also stable in water and common organic solvents. More interestingly, desolvated HOF-8 exhibits high CO2 adsorption as well as highly selective CO2 and C6H6 adsorption at ambient temperature.

Selective Cross-Dehydrogenative Coupling of Various Acyclic Enamides with Heteroarenes via Rh(III)-Catalyzed C-H Activation.

The developed methodology describes an efficient Rh(III)-catalyzed oxidative C-H/C-H cross-coupling between acyclic enamides and heteroarenes. This cross dehydrogenative coupling (CDC) reaction offers advantages, including excellent regioselectivity and stereoselectivity, good functional group compatibility, and a broad substrate scope. Mechanistically, Rh(III)-catalyzed ß-C(sp2)-H activation of acyclic enamides is proposed to be the critical step.

Palladium-catalyzed phosphorylation of arylsulfonium salts with P(O)H compounds via C-S bond cleavage.

Herein we report a novel palladium-catalyzed phosphorylation of arylsulfonium salts with P(O)H compounds via C-S bond cleavage under mild conditions. The protocol provides a pragmatic strategy applicable to the synthesis of diverse arylphosphonates.

Self-assembled sonogels formed from 1,4-naphthalenedicarbonyldinicotinic acid hydrazide.

In this paper, we report self-assembled sonogels formed from 1,4-naphthalenedicarbonyldinicotinic acid hydrazide (NDC-NN3) in some liquids including ethanol, tetrahydrofuran (THF), 1,4-dioxane, n-propanol, n-butanol and n-pentanol. When the clear solution of NDC-NN3 in the selected liquids mentioned above at a suitable concentration was irradiated with ultrasound waves at room temperature, a sonogel was formed. Upon heating, the sonogel dissolved gradually and finally became a clear solution again. Upon cooling the hot solution to room temperature, the solution state did not change even after standing for a few days. Nevertheless, if the solution underwent sonication for a certain time, a stable gel was obtained again. The critical gelation concentrations (CGCs) of NDC-NN3 in ethanol, THF, 1,4-dioxane, n-propanol, n-butanol and n-pentanol are 10, 8, 6, 8, 6 and 8 mg mL-1, respectively. The obtained sonogels display excellent mechanical properties. The crystal structure of NDC-NN3 suggests that the naphthalene ring, hydrazide group and the position of N in the pyridine ring mediate the self-assembly process. Upon sonication, the formation of suitable π-π stacking and intermolecular hydrogen bonding drives the gelator molecules to self-assemble into fibers, spheres and micro-burdock-shaped balls in various solvents, which ultimately confine the liquids.

Rhodium(III)-Catalyzed Direct C-H Arylation of Various Acyclic Enamides with Arylsilanes.

The stereoselective ß-C(sp2)-H arylation of various acyclic enamides with arylsilanes via Rh(III)-catalyzed cross-coupling reaction was illustrated. The methodology was characterized by extraordinary efficacy and stereoselectivity, a wide scope of substrates, good functional group tolerance, and the adoption of environmentally friendly arylsilanes. The utility of this present method was evidenced by the gram-scale synthesis and further elaboration of the product. In addition, Rh(III)-catalyzed C-H activation is considered to be the critical step in the reaction mechanism.

Supramolecular gel formation regulated by water content in organic solvents: self-assembly mechanism and biomedical applications.

As one of the most important and fruitful methods, supramolecular self-assembly has a significant advantage in designing and fabricating functional soft materials with various nanostructures. In this research, a low-molecular-weight gelator, N,N'-di(pyridin-4-yl)-pyridine-3,5-dicarboxamide (PDA-N4), was synthesized and used to construct self-assembled gels via a solvent-mediated strategy. It was found that PDA-N4 could form supramolecular gels in mixed solvents of water and DMSO (or DMF) at high water fraction (greater than or equal to 50%). By decreasing the water fraction from 50% to 30%, the gel, suspension and solution phases appeared successively, indicating that self-assembled aggregates could be efficiently modulated via water content in organic solvents. Moreover, the as-prepared PDA-N4 supramolecular gels not only displayed solid-like behavior, and pH- and thermo-reversible characteristics, but also showed a solution-gel-crystal transition with the extension of aging time. Further analyses suggested that both the crystal and gel had similar assembled structures. The intermolecular hydrogen bonding between amide groups and the π-π stacking interactions between pyridine groups played key roles in gel formation. Additionally, the release behavior of vitamin B12 (VB12) from PDA-N4 gel (H2O/DMSO, v/v = 90/10) was evaluated, and the drug controlled release process was consistent with a first-order release mechanism. The human umbilical venous endothelial cell culture results showed that the PDA-N4 xerogel has good cytocompatibility, which implied that the gels have potential biological application in tissue engineering and controlled drug release.

A multiaxial lead-free two-dimensional organic-inorganic perovskite ferroelectric.

Two-dimensional (2D) hybrid organic-inorganic perovskites (HOIPs) have recently gained tremendous interest because of their unique features in contrast to three-dimensional counterparts and traditional 2D materials. However, although some 2D HOIP ferroelectrics have been achieved, the issue of toxic Pb and uniaxial nature impede their further application. Herein, for the first time, we report a lead-free 2D HOIP multiaxial ferroelectric, [3,3-difluorocyclobutylammonium]2CuCl4 (1), which shows four ferroelectric axes and eight equivalent polarization directions, more than those of the other 2D HOIP ferroelectrics and even the inorganic perovskite ferroelectric BaTiO3 (three ferroelectric axes and six equivalent polarization directions). 1 also features a high Curie temperature of 380 K and exhibits remarkable thermochromism of color change from green-yellow to dark brown. To our knowledge, 1 is the first multiaxial lead-free 2D HOIP ferroelectric. This work sheds light on the exploration of better lead-free 2D HOIP ferroelectrics.

Supramolecular organogels fabricated with dicarboxylic acids and primary alkyl amines: controllable self-assembled structures.

Supramolecular organogels are soft materials comprised of low-molecular-mass organic gelators (LMOGs) and organic liquids. Owning to their unique supramolecular structures and potential applications, LMOGs have attracted wide attention from chemists and biochemists. A new "superorganogel" system based on dicarboxylic acids and primary alkyl amines (R-NH2) from the formation of organogels is achieved in various organic media including strong and weak polar solvents. The gelation properties of these gelators strongly rely on the molecular structure. Their aggregation morphology in the as-obtained organogels can be controlled by the solvent polarity and the tail chain length of R-NH2. Interestingly, flower-like self-assemblies can be obtained in organic solvents with medium polarity, such as tetrahydrofuran, pyridine and dichloromethane, when the gelators possess a suitable length of carbon chain. Moreover, further analyses of Fourier transformation infrared spectroscopy and 1H nuclear magnetic resonance spectroscopy reveal that the intermolecular acid-base interaction and van der Waals interaction are critical driving forces in the process of organogelation. In addition, this kind of organogel system displays excellent mechanical properties and thermo-reversibility, and its forming mechanism is also proposed.

Rh(iii)-catalyzed C-7 arylation of indolines with arylsilanes via C-H activation.

Site-selective synthesis of C-7 arylated indolines has been achieved via oxidative arylation of indolines with arylsilanes under Rh(iii)-catalyzed C-H activation of indolines by using CuSO4 as a co-oxidant. This transformation has been explored for a wide range of substrates under mild conditions.

A pH-/thermo-responsive hydrogel formed from N,N'-dibenzoyl-l-cystine: properties, self-assembly structure and release behavior of SA.

In this study, we report a pH-/thermo-responsive hydrogel formed by N,N'-dibenzoyl-l-cystine (DBC). It is difficult to dissolve DBC in water even on heating, and it exhibits no gelation ability. Interestingly, DBC is readily soluble in NaOH solution at room temperature and the self-assembled hydrogels are obtained by adjusting the basic DBC aqueous solution with HCl to achieve a given pH value (<3.5). When NaOH is added to the hydrogel (pH > 9.4), it becomes a sol again. This small-molecule hydrogel is characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, rheological measurement and differential scanning calorimetry. The results indicate that the DBC hydrogel exhibits excellent mechanical properties, thermo-reversibility, and pH-responsive properties. Fortunately, the single crystal of DBC is obtained by volatilizing its acid aqueous solution. It crystallizes in the monoclinic space group P21 (Z = 2) with lattice parameters a = 10.8180 (11) Å, b = 9.0405 (9) Å, c = 10.9871 (11) Å and ß = 90.798 (3)°. By comparing the X-ray diffraction result of the DBC single crystal with that of its xerogel, the self-assembled structure of DBC in hydrogel has been ascertained. The gelators are self-assembled via strong intermolecular hydrogen bonds linking neighboring amide and carboxyl groups, π-π stacking interactions for aromatic rings, and hydrogen bonds between water molecules. In addition, the release behavior of salicylic acid (SA) molecules from the DBC gel is also investigated taking into account the DBC concentration, phosphate buffer solution (PBS) pH and SA concentration. When the concentrations of DBC and SA are 3.0 g L-1 and 200 mg L-1, respectively, the release ratio in PBS (pH = 4.0) reaches 58.02%. The diffusion-controlled mechanism is in accordance with Fickian diffusion control within the given time range.

Ar-P bond construction by the Pd-catalyzed oxidative cross-coupling of arylsilanes with H-phosphonates via C-Si bond cleavage.

A novel and efficient methodology that allows for the construction of Ar-P bonds via the Pd-catalyzed oxidative cross-coupling reaction of various arylsilanes with H-phosphonates leading to valuable arylphosphonates has been developed.

A two-dimensional copper(II) coordination polymer based on 2-propyl-1H-imidazole-4,5-dicarboxylic acid.

Single-crystal X-ray diffraction analysis of poly[bis(µ2-5-carboxy-2-propyl-1H-imidazole-4-carboxylato-κ(3)N(3),O(4):O(5))copper(II)], [Cu(C8H9N2O4)2)]n, indicates that one carboxylic acid group of the 2-propyl-1H-imidazole-4,5-dicarboxylic acid (H3PDI) ligand is deprotonated. The resulting H2PDI(-) anion, acting as a bridge, connects the Cu(II) cations to form a two-dimensional (4,4)-connected layer. Adjacent layers are further linked through interlayer hydrogen-bond interactions, resulting in a three-dimensional supramolecular structure.

Vesicle formation induced by metal ions from micelle-forming sodium hexadecylimino diacetate in dilute aqueous solution.

In dilute aqueous solution, micelle-forming sodium hexadecylimino diacetate assembles into vesicles induced by Cu(II), Co(II) and Ni(II) ions.

Strong blue-fluorescence-emitted stable monolayers formed in organic solvents by a coordination polymer with long-chained bis-Schiff base.

The coordination polymer, P(ZnL) (L=N,N'-bis[2-hydroxy-4-(dodecyloxy)benzaldehyde)]-ethylenedimine), forms a novel uniform lamellar superstructure in organic liquids, which exhibits intense fluorescence in organic dispersions as well as in the corresponding cast films.