The title compounds, 3,5,7‐triphenyl‐1,2‐diazacyclohepta‐1(7),2‐diene, C23H20N2, (I), and 3,7‐bis(2‐hydroxyphenyl)‐5‐phenyl‐1,2‐diazacyclohepta‐1(7),2‐diene, C23H20N2O2, (II), constitute the first structurally characterized examples of seven‐membered heterocycles with 1,2‐diaza ring N atoms. Compound (I) crystallizes in the space group P, with two independent molecules in the asymmetric unit that differ in the conformation of one of the phenyl rings, while (II) crystallizes in the space group C2/c. The C5N2 ring in each of (I) and (II) adopts a twist‐boat conformation. Compound (I) exhibits neither C—H...π interactions nor π–π stacking interactions, whereas (II) shows both intramolecular O—H...N hydrogen bonds and a C—H...π interaction that joins the molecules into an infinite chain in the [010] direction. 相似文献
The three component reaction of aromatic aldehydes and 1,3‐indandione in the presence of 4‐amino‐6‐hydroxy‐2‐mercaptopyrimidine is catalyzed by active kappa‐carrageenan under mild conditions to afford the desired products in clean reaction profiles. The kappa carrageenan sources are bioavailable and are extracted from Chondrus crispus, a red seaweed. The catalyst could be prepared by mixing of kappa‐carrageenan in a mechanical mortar for 5 min in a simple step. Good yields with superior atom economy, green and recyclable catalyst with natural source, and simple work‐up are the main advantages of the method for the synthesis of dihydropyridopyrimidines. 相似文献
Reduced graphenes (belonging to the class of chemically modified graphenes, CMG) are one of the most investigated and utilized materials in current research. Oxygen functionalities on the CMG surfaces have dramatic influences on material properties. Interestingly, these functionalities are rarely comprehensively characterized. Herein, the four most commonly used CMGs, mainly electrochemically reduced graphene oxide (ER‐GO), thermally reduced graphene oxide (TR‐GO), and the corresponding starting materials, that is, graphene oxide and graphite oxide, were comprehensively characterized by a wide variety of methods, such as high‐resolution X‐ray photoelectron spectroscopy, electrochemical impedance spectroscopy, UV/Vis spectroscopy, transmission electron microscopy (TEM), and voltammetry, to establish connections between the structures of these materials that carry different oxygen functionalities and their electrochemical behaviors. This was followed by the quantification of the negatively charged oxygen‐containing groups (OCGs) by UV/Vis spectroscopy and of the electrochemically reducible OCGs by voltammetry. Lastly, a biofunctionalization with gold nanoparticle (AuNP)‐modified DNA sequences was performed by the formation of covalent bonds with the carboxylic groups (? COOH) on the CMG surfaces. There was an evident predominance of functionalizable ? COOH groups on the ER‐GO surface, as confirmed by a higher amount of Au detected both with differential‐pulse voltammetry and impedance spectroscopy, coupled with visualization by TEM. We exploited the DNA–Au bioconjugates as highly specific stains to localize and visualize the positions of carboxylic groups. Our findings are very important to clearly identify the presence, nature, and distribution of oxygen functionalities on different chemically modified graphenes. 相似文献
A series of metal compounds (M = Al, Ti, W, and Zn) containing pyrrole‐imine ligands have been prepared and structurally characterized. The reactions of AlMe3 with one and three equivs of pyrrole‐imine ligand [C4H3NH‐(2‐CH=N? CH2Ph)] ( 1 ) generated aluminum compounds Al[C4H3N‐(2‐CH=N? CH2Ph)]Me2 ( 2 ) and Al[C4H3N‐(2‐CH=NCH2Ph)]3 ( 3 ), respectively, in relatively high yield. Reacting two equivs of 1 with Ti(OiPr)4, W(NHtBu)2(=NtBu)2, or ZnMe2 afforded Ti[C4H3N‐(2‐CH=NCH2Ph)]2(OiPr)2 ( 4 ), W[C4H3N‐(2‐CH=NCH2Ph)]2(=NtBu)2 ( 5 ), and Zn[C4H3N‐(2‐CH=NCH2Ph)]2 ( 6 ), respectively. All the compounds have been characterized by 1H and 13C NMR spectroscopy. Compounds 3 – 6 have also been characterized by single‐crystal X‐ray structural analysis. The biting angles of pyrrole‐imine ligand with metals decrease and their related M? Npyrrole and M? Nimine bond lengths increase in the order of 6 , 3 , 4 , and 5 . 相似文献
Modified 3,5‐dipyrrolylpyrazole (DPP) derivatives in their protonated form produce planar [2+2]‐type complexes with trifluoroacetate (TFA) ions. These complexes serve as constituent components of ion‐pair‐based assemblies. An essential strategy for the construction of dimension‐controlled organized structures based on these [2+2]‐type complexes is the introduction of aryl rings bearing long alkyl chains, which enables the formation of 2D patterns at interfaces, supramolecular gels, and mesophases. 相似文献
Using 3‐Aminopropyltriethoxysilane(APTES) as a single silica source, an amino‐rich ultrafine organosilica‐nanoparticle‐modified Au electrode was fabricated, following the formation of (3‐mercaptopropyl)‐trimethoxysilane (MPTS) monolayer on Au surface (MPTS/Au). With cetyltrimethylammonium bromide as an additive, APTES‐based gel particles on the electrode have a narrow particle size distribution of 4–7 nm and “crystal‐like” structure. AFM and electrochemical characterization confirmed the successful grafting of APTES nanoparticles on MPTS/Au. The APTES/MPTS/Au electrode is highly sensitive for the detection of copper(II) ions with a detection limit as low as 1.6×10?12 mol L?1 (S/N>3) by square wave voltammetry. The current is linear to copper(II) concentration between 1.6×10?12 and 6.25×10?10 mol L?1. 相似文献
We report the electrochemical deposition of a β‐cyclodextrin pyrrole conjugate (Py‐β‐CD) on an electrode surface including i) characterization based on surface‐enhanced Raman scattering and field‐emission scanning electron microscopy; ii) studies of the molecular recognition of enantiomers of phenylalanine methyl ester hydrochlorides (Phe) based on linear sweep voltammetry and a quartz crystal microbalance. The PPy‐β‐CD polymeric layer on a metallic substrate is distinguished by its inhomogeneity, in which both highly ordered β‐CD units and highly disordered polymer chains are observed. The voltammetric recognition results showed that PPy‐β‐CD exhibited a higher sensitivity for d ‐Phe (138±15)×103 than for l ‐Phe (6±1)×103 within the concentration range 0.1–0.75 mM (n=3) despite the differences in the polymer arrangement on the surface. A possible mechanism of molecular recognition of phenylalanine enantiomers is discussed. 相似文献
Of the various beyond‐lithium‐ion batteries, lithium–sulfur (Li‐S) batteries were recently reported as possibly being the closest to market. However, its theoretically high energy density makes it potentially hazardous under conditions of abuse. Therefore, addressing the safety issues of Li‐S cells is necessary before they can be used in practical applications. Here, we report a concept to build a safe and highly efficient Li‐S battery with a flame‐inhibiting electrolyte and a sulfur‐based composite cathode. The flame retardant not only makes the carbonates nonflammable but also dramatically enhances the electrochemical performance of the sulfur‐based composite cathode, without an apparent capacity decline over 750 cycles, and with a capacity greater than 800 mA h?1 g?1(sulfur) at a rate of 10 C. 相似文献
Palladium and platinum complexes containing a sulfur‐functionalised N‐heterocyclic carbene (S‐NHC) chelate ligand have been synthesised. The absolute conformations of these novel organometallic S‐NHC chelates were determined by X‐ray structural analyses and solution‐phase 2D 1H–1H ROESY NMR spectroscopy. The structural studies revealed that the phenyl substituents on the stereogenic carbon atoms invariably take up the axial positions on the Pd‐C‐S coordination plane to afford a skewed five‐membered ring structure. All of the chiral complexes are structurally rigid and stereochemically locked in a chiral ring conformation that is either (Rs,S,R)‐λ or (Ss,R,R)‐δ in both the solid state and solution. 相似文献
Tetrahydroisoquinolines and tetrahydrobenzazepines were prepared by acid‐promoted ring contraction of cyclic ureas, which were themselves formed by ring expansion of indolines and tetrahydroquinolines. The consequent overall one‐carbon insertion reaction gives these 6‐ and 7‐membered heterocyclic scaffolds in three steps from readily available precursors. Other ring sizes may be formed by an alternative elimination reaction of bicyclic structures. Scalability of the method was demonstrated by operating it in a flow system. 相似文献
Clinacanthus nutans has been used in traditional herbal medicine for cancer prevention, but the specific bioactive compounds responsible for the observed activities have not been explored. Different polar solvents such as methanol, chloroform, ethyl acetate, and hexane were used for the extraction. The extracts, fractions, and isolated compounds were subjected to DPPH and ferric reducing antioxidant potential (FRAP) assays. Methanol extracts show significant free‐radical scavenging activity of 69.09% in DPPH and 56.49% FRAP. Purification of MeOH extracts afforded the fraction FB28 and two new sulfur‐containing compounds, named clinamide D and E ( 1 , 2 ). Compound ( 1 ) proved to be more active with an IC50 value for DPPH radical scavenging of 118.27 ± 0.01 µg/mL and reduction of Fe3+–TPTZ complex of 386.24 ± 0.02, higher than that of the standard ascorbic acid. Sulfur‐containing compounds isolated from C. nutans is a potential natural antioxidant. 相似文献
When Ar is a low‐aromaticity homo‐ or heterosystem, the sulfonyl‐stabilized anion of nitrobutadienes 4 (which derive from the initial ring opening of 3‐nitrothiophene) undergoes a rather surprising addition onto the aromatic ring itself, thereby leading to the construction of an unusual eight‐membered sulfur heterocycle condensed with the original Ar ring. The competitiveness of such a pathway with respect to the formation of the thiopyran ring (i.e., addition onto the nitrovinyl moiety) is favored at low temperatures, thus revealing its nature as a kinetically controlled process. 相似文献
Novel boron‐dipyrromethene (BODIPY)‐bridged 22‐oxacorrole dyads, using meso‐pyrrolyl 22‐oxacorrole as a key synthon, have been synthesized. The reactivity of the meso‐pyrrolyl group of 22‐oxacorrole was exploited to synthesize the first examples of BODIPY‐bridged 22‐oxacorrole dyads in ≈40 % yield. The dyads are stable and exhibited interesting spectral and electrochemical properties. 相似文献
Commercially available 1,2‐PB was transformed into a well‐defined reactive intermediate by quantitative bromination. The brominated polymer was used as a polyfunctional macroinitiator for the cationic ring‐opening polymerization of 2‐ethyl‐2‐oxazoline to yield a water‐soluble brush polymer. Nucleophilic substitution of bromide by 1‐methyl imidazole resulted in the formation of polyelectrolyte copolymers consisting of mixed units of imidazolium, bromo, and double bond. These copolymers, which were soluble in water without forming aggregates, were used as stabilizers in the heterophase polymerization of styrene and were also studied for their ionic conducting properties.