CN Double Bond Research Articles

Inspired corrosion resistance of copper mediated by multiple ethoxy units linker included indazole based bis-Schiff base dyes in NaCl solution

In this study, hydrophilic multiple ethoxy units linkage chain included bis-Schiff base dyes (SBs 1–3) were designed and synthesized for strengthening corrosion resistance of copper in NaCl solution. The corrosion resistance and corrosion inhibition mechanism of the target dyes for copper were investigated in 3.0 wt% NaCl solution. The adsorption of these dyes on copper surface was revealed by Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) revealed the adsorption of these dyes containing CN double bonds on copper surface, achieving excellent corrosion inhibition efficiency. The electrochemistry shows that the dyes were able to inhibit the corrosion of copper in sodium chloride solution, and the corrosion inhibition efficiency reached the peak value at a concentration of 1.00 mM. It is noted that the corrosion inhibition efficiency increased with the number increase of ethoxy units. The kinetic potential polarization curves indicate that the dyes were anodic corrosion inhibitors, which could inhibit the anodic reaction process of corrosion. The adsorption of corrosion inhibitor these dyes on copper surface followed Langmuir isothermal adsorption model.

A highly sensitive Golgi-targeted fluorescent probe for the simultaneous detection of malondialdehyde and formaldehyde in living systems and foods

Malondialdehyde (MDA) and formaldehyde (FA) are highly active carbonyl substances widely present in both biological and abiotic systems. The detection of MDA and FA is of great significance for disease diagnosis and food safety monitoring. However, due to the similarity in structural properties between MDA and FA, very few probes for synergistically detecting MDA and FA were reported. In addition, functional abnormalities in the Golgi apparatus are closely related to MDA and FA, but currently there are no fluorescent probes that can detect MDA and FA in the Golgi apparatus. Therefore, we constructed a simple Golgi-targetable fluorescent probe GHA based on hydrazine moiety as the recognition site to produce a pyrazole structure after reaction with MDA and to generate a CN double bond after reaction with FA, allowing MDA and FA to be distinguished due to different emission wavelengths during the recognition process. The probe GHA has good specificity and sensitivity. Under the excitation of 350 nm, the blue fluorescence was significantly enhanced at 424 nm when the probe reacted with MDA, and the detection limit was 71 nM. At the same time, under the same excitation of 350 nm, the reaction with FA showed a significant enhancement of green fluorescence at 520 nm, with a detection limit of 12 nM for FA. And the simultaneous and high-resolution imaging of MDA and FA in the Golgi apparatus of cells was achieved. In addition, the applications of the probe GHA in food demonstrated it can provide a powerful method for food safety monitoring. In summary, this study offers a promising tool for the synergistic identification and determination of MDA and FA in the biosystem and food, facilitating the revelation of their detailed functions in Golgi apparatus and the monitoring of food safety.

Reversible C═N Bond Formation Controls Charge-Separation in an Aza-Diarylethene Photoswitch.

Diarylethenes belong to the most eminent photoswitches and have been studied for many decades. They are found in virtually every field of application and have become highly valuable molecular tools for instilling light-responsiveness into materials, catalysts, biological systems, or pharmacology. In this work, we present a novel and distinct type of pyrimidine-based aza-diarylethene, which undergoes a highly unusual zwitterion-forming photoreaction. During this fully reversible process, a CN double bond is established under concomitant aromatization and thiophene-ring opening. The metastable zwitterion thus possesses a positively charged extended aromatic structure and an independent conjugated thiolate function. It can further photoisomerize between a more stable Z and a less stable E isomer, resulting in effective four-state photoswitching. Unusual for diarylethenes, the metastable isomers show negative solvatochromism and red-shifted absorption in apolar solvents. With this behavior, aza-diarylethenes effectively bridge the properties of merocyanines and diarylethenes. Thermal stability of the zwitterions can be modulated from very labile to highly stable behavior in response to pH, again in a fully reversible manner. Pyrimidine-based aza-diarylethene thus establishes a unique photoreaction mechanism for diarylethenes, allowing control of charge separation, thermal stability, and color generation in a different way than hitherto possible.

Leaching of catalyst platinum from cured silicone elastomers: A preliminary study for comparing reagents

Addition curing systems involve two-part silicones which require the mixture of a silicone polymer with a catalyst to initiate the cure. Platinum is the most commonly used metal catalyst for addition curing of silicones by hydrosilylation which involves the crosslinking by the addition reaction of silicon hydride species to unsaturated bonds, mainly CC, but also CO or CN double bonds. After crosslinking of the polymers, the platinum catalyst cannot be recovered but remains in the silicone materials throughout the entire product life. In the end, platinum is disposed of together with the silicones and is thus lost to the value chain. The overall objective of this work was to develop a recycling process for the recovery of platinum from addition-cured silicone elastomers. In the first step, this was achieved by efficient digestion methods and by optimizing the leaching processes for exemplary commercial silicone elastomer products. Two different silicone materials were investigated, both of which were crosslinked with a platinum catalyst. The initial Pt content in the tested samples was 12.6 ± 0.2 mg/kg for a commercial silicone impression material and 6.3 ± 0.5 mg/kg for a silicone baking mold, measured by graphite furnace atomic absorption spectrometry (GF-AAS). Samples were first frozen with liquid nitrogen to improve brittleness and then crushed with a simple food processor to obtain a silicone granule. Various acid mixtures, mainly based on sulfuric acid, were investigated as digestion methods in order to extract platinum from the silicone network. These had different effects on the dissolution behavior of silicone samples and the amount of platinum extracted in each case. The amount of platinum leached from the filtrate of the digested samples in each case was measured by ICP-OES to evaluate the efficiency of different leaching mixtures. In addition, the dissolved platinum species present in the solutions was identified by UV/VIS as tetrachloridoplatinate(II) complex. The best platinum leaching results so far were obtained with two methods, both of which used a leaching mixture based on sulfuric acid and hexamethyldisiloxane (M2). In the presence of hydrochloric acid, 9.6 ± 1.6 mg platinum/kg was leached from the silicone impression material and 4.2 ± 0.8 mg platinum/kg from the silicone baking mold. With the additional use of aqua regia instead of hydrochloric acid, 10.4 ± 2.8 mg platinum/kg was extracted from the silicone impression material and 4.8 ± 1.0 mg platinum/kg was extracted from the silicone baking mold. These methods were replicated with n = 3. Using statistical evaluation methods (F-test, t-test, and confidence interval), no significant difference was found between these two best methods. Recovery of platinum(0) from leach mixtures has not yet been achieved due to high dilution and very low platinum concentration in samples and will be part of another study.

Rational design of aza-BODIPY derived near-infrared fluorescent probe for CN− in aqueous solutions

The lethal toxicity of cyanide ions has inspired the development of fluorescent probes for their recognition, but fluorescent probes that can selectively bind cyanide ions in aqueous solution have been a challenge. In this paper, the electron-donor/withdrawing groups were introduced to aza-BODIPY fluorophore to discover the optical properties and tune the addition reaction with CN−. The push-pull electron effect of the corresponding substituents in aza-BODIPY makes the spectral shifts, molar extinction coefficients and fluorescence quantum yields remarkably different. The introduction of the electron-withdrawing group (–CF3) to aza-BODIPY (CF3-BDP) resulted in the electron-deficient property of the CN double bond, and the ability of nucleophilic addition of CN− to CF3-BDP was enhanced in aqueous solutions. Due to the collapse of the conjugated structure after the addition, the fluorescence of CF3-BDP was rapidly quenched to realize the highly sensitive response to CN−. According to DFT calculation, the reaction site of controversial mechanism was verified to the CN band in the pyrrole of aza-BODIPY. Furthermore, CF3-BDP was proved to have the ability to detect cyanide in biological system.

Exploring of catalytic oxygen reduction reaction activity of lattice carbons of vanadium and niobium doped nitrogen codoped carbon nanotubes by density functional theory

AbstractThe oxygen electroreduction mechanism on the V‐ and Nb‐doped nitrogen‐codoped (6,6)armchair carbon nanotube with incorporated MN4 fragment has been studied using the ωB97XD and PBE density functional theory approaches. The metal center in MN4 fragment and the adjacent NCCN double bond (C2 site) of the support have been revealed as active centers. The metal active centers turned out to be irreversibly oxidized at the first step of ORR affording stable O*, 2O*, or O*HO* adsorbates depending on the applied electrode potential U, that makes them no longer active in ORR. Therefore, the C2 site comes at the forefront in ORR catalysis. Among the metal oxidized forms M(O)N4, M(O)(O)N4, and M(O)(OH)N4CNT, the C2 site of the latter turned out to be most active for 4e dissociative ORR. For both metals the last protonation/electron transfer step, HO* + H* → H2O, is the rate‐limiting step. The alternative hydrogen peroxide formation is not only thermodynamically less favorable but also kinetically slower than the 4e dissociative ORR route on the C2 site of model M(O)(OH)N4CNT catalyst.

Photodegradation of enestroburin in water by simulated sunlight irradiation: Kinetics, isomerization, transformation products identification and toxicity assessment

Enestroburin is the first strobilurin fungicide developed by China and has been widely used to control fungal disease for 15 years. Investigation of its photolytic behaviour is essential for the comprehensive evaluation of its ecological risk. The effects of solution pH, humic acid (HA) and Fe(III) ions on photolysis were studied. The direct photolysis rates of enestroburin in the acidic solution (pH = 4) was faster than that in the basic (pH = 7) or neutral condition (pH = 9). HA and Fe3+ ions inhibited photolysis by the light screening effect. The photolysis of enestroburin was very fast due to the generation of photo-isomers. Seven isomeric products of enestroburin were observed using SFC-MS/MS, and the reaction mechanism for photo-induced isomers was proposed. The reaction occurred on three double bonds, including tautomerism of enol ether and oxonium and the triplet energy transfer of the CC and CN double bond. 12 transformation products (TPs) were identified by screening suspect compounds and non-target compounds, and one product (M-381) was synthesized for confirmation and quantification. A probable transformation mechanism was suggested based on the identified TPs and DFT calculations. The main transformation reactions included hydration, hydrolysis, oxidation, reduction and decarboxylation. Finally, the toxicities of the identified TPs and parent compound to aquatic organisms were predicted using ECOSAR software, and the toxicities of enestroburin and M-381 to daphnia magna were tested in the laboratory. The toxicity classification proposed by ECOSAR is reliable to a certain extent. Enestroburin and 2 TPs (M-313 and M-327) were classified as “very toxic”, which may pose a potential threat to aquatic ecosystems.

Protonated g-C3N4-based nonvolatile memories with good environmental robustness assisted by boron nitride

The searching for new memory that can work under harsh conditions will be significant for their application in some important fields such as geothermal, oil and aerospace industries. In this work, memory devices with simple sandwich structures using the g-C3N4 treated by different concentration acids as active layers have been fabricated, which exhibit non-volatile behaviors and bipolar switching characteristics. Protonation treatment can enhance the memory performance efficiently compared with un-protonized device. Among them, the device containing g-C3N4 treated with 8 M HCl presents the best resistive switching performance with ON/OFF ratio of 104 and good retention capability, which might be relative to its texture without violent tortuosity. In addition, the protonated g-C3N4-based memory devices exhibit good environmental robustness, including temperature and ionizing irradiation. Specially, its high tolerant temperature (454 °C) can also be assisted by doping BN for heat dissipation. Their good thermal/irradiating stabilities are assigned to the strong bond energy of CN double bonds localized π-conjugated tri-s-triazine rings. In all, the facial protonation treatment without any functionalization or supporting, the simple sandwich device structure and good environmental robustness endow their promising applications in aerospace and outdoor environment.

Carbon nanotube‐based titanium‐ and zirconium‐doped [M–N4] type ORR catalysts. First principle study

AbstractThe efficiency of the Ti‐ and Zr‐doped nitrogen‐codoped carbon nanomaterials based on the (6,6)armchair carbon nanotube C120H24 with incorporated MN4 fragment has been analyzed using the first principle method at the DFT theory level. Two active sites on the catalyst surface have been revealed: the MN4 site and the adjacent NC═CN double bond (C2 site) of the support. A distinctive feature of Ti and Zr metals is that the MN4 site remains active even in the oxidized forms, although the C2 site becomes competitive. The free energy diagrams of the ORR were plotted for associative and dissociative mechanisms for both the initial and different oxidized forms in the acidic and alkaline media. The intermediates corresponding to the global minima were determined depending on the applied electrode potential and on the nature of the metal. Slightly lower exothermicity of oxygen adsorption and lower‐lying intermediates of the same type for Ti metal are indicative of some advantage of the Ti‐doped over the Zr‐doped MN4–CNT catalysts.

Nickel-catalyzed formal [3 + 2]-cycloaddition of 2H-azirines with 1,3-dicarbonyl compounds for the synthesis of pyrroles

An efficient nickel-catalyzed formal [3 + 2]-cycloaddition of 2H-azirines with 1,3-dicarbonyl compounds for the synthesis of tetrasubstituted pyrroles has been developed. This transformation involves cleavage of the CN double bond and the construction of new CC and CN bonds. The reaction employs readily available starting materials, tolerates a wide range of functional groups, and affords tetrasubstituted pyrroles in good to high yields under mild reaction conditions. A gram-scale reaction was performed to demonstrate the scale-up applicability of this synthetic method.

A water-soluble colorimetric and fluorescent probe for rapidly sensing of ClO− in organisms

A simple colorimetric and fluorescent probe bearing coumarin and p-toluenesulfonyl hydrazide moieties was developed, which was capable of displaying excellent selectivity for hypochlorite. The distinct absorption spectral shift (49 nm) was induced by ClO−-triggered oxidative hydrolysis of CN double bonds in aqueous solution, which was accompanied by the optical variation from yellow to colorless. Besides, this probe solution underwent a dramatic intensification (162-fold) of the fluorescence signaling at 444 nm via the addition of ClO− (3 equiv.) within a short time. More importantly, the results achieved by fluorescence spectra revealed an excellent linear relation of probe 1 for ClO− with excellent sensitivity (9.1 nM). Further, the good recoveries and cellular experiments verified the prospective functions of this probe in real water environment and SW 480 cells.

New thiazoldinone substituted 2,6-diarypiperidin-4-one: Synthesis, crystal structure, spectral characterization, binding mode with calf thymus DNA

A series of 2,6-diarylpiperidin-4-ylidene thiazolidin-4-one derivatives (15–21) were efficiently synthesized using a green and recyclable catalyst Amberlit IR-120H resin under microwave irradiation. All the compounds were characterized by elemental analysis, FT-IR, 1H, 13C NMR spectra. The conformation of the compound was unambiguously assigned by 2D NMR spectral analysis. Single crystal X-ray diffraction recorded for compound 21 and the data indicate that the compound crystallized in triclinic system with space group Pī. The observed chemical shifts and coupling constants suggested that the piperidone ring (15–21) adopts in chair conformation with equatorial orientations of the aryl groups. In solid state the configuration about CN double bond is syn to C-5 carbon. All the compounds were screened for their in vitro antibacterial and antimycobacterial activities. Among the tested, compounds 17 and 18, were found to be potent inhibition with MIC values in the range of 0.2–0.8 μg/mL.The interactions of the compounds with calf thymus DNA were investigated by spectroscopic method and the results indicated that compounds bound to Deoxyribo Nucleic Acid (DNA) by groove binding mode.

Solvothermal synthesis of novel phenylpyrazole Schiff base fluorescent insecticides fused extended conjugate units for enhancing bioactivities, photophysical and electrochemical properties

In order to find a new type of fluorescent insecticides, a series of phenylpyrazole Schiff base derivatives have been synthesized by a facile one-pot solvothermal method based on the amino group of fipronil addition-elimination condensation reaction with the corresponding benzaldehyde derivatives in high yields, which were fully characterized by 1H NMR, IR, MS and elemental analysis. Crystal structure determination indicated that 1-(2,6-dichloro-4-(trifluoromethyl)phenyl)-5-(4-fluoro-benzylidene-amino)-4-(trifluoromethylsulfinyl)-1H-pyrazole-3-carbonitrile (7) crystallized into zigzag chains by π···π packing interactions between phenyl rings of neighbouring molecules. The investigation for insecticidal bioactivities of these pesticides against 3rd instar larvae of Plutella xylostella exhibited better activities than that of fipronil, which can be elucidated by enhanced calcium ions' coordination abilities with CN double bonds and chloride ions, extended conjugated parent structure, steric hindrance of the stereoscopic structure and electronegativity of substituted groups. The electronic absorption, fluorescent and electrochemical properties of phenylpyrazole Schiff base derivatives have been systematically investigated for the first time, which all emitted blue-green light in both solution and solid state at room temperature. The relationships between extended conjugated moieties of parent structure, positions of substituent group and the kinds of substitutes at 4-position on the phenyl ring and photophysical properties have been discussed, which was confirmed by electrochemical analysis. The alteration of absorption and emission wavelengths can be rationalized by substitutes' electronegativity and Substituents’ Hammett constants. The fluorescent quantum yields of phenylpyrazole Schiff base insecticides were almost 4 times that of Fipronil, which laid a foundation for their natural degradation and fluorescence detection of pesticide residues. This approach proposes a unique insight to provide a great number of novel phenylpyrazole Schiff base fluorescent insecticides by a general green method.

Novel synthesis of 1,4-thiazin-2-one O-(tert-butyl) oximes and benzo[b][1,4]thiazin-2-one O-(tert-butyl) oximes in the presence of K2CO3/SiO2

A simple and efficient method was developed for the synthesis of 1,4-thiazin-2-one O-(tert-butyl) oximes and benzo[b][1,4]thiazin-2-one O-(tert-butyl) oximes from N-tert-butoxy acyl imidoyl bromides and 2-aminothiols in the presence of K2CO3/SiO2. Twenty five novel compounds were readily synthesized in excellent yields using this procedure. The products possessed Z-stereochemistry with regard to the CN double bond. The reaction proceeded with initial substitution of bromine in the N-tert-butoxy acyl imidoyl bromides by mercapto groups in the presence of K2CO3/SiO2, and subsequent intramolecular Schiff base formation.

Synthesis, spectroscopic characterization, crystal structure, Hirshfeld surface analysis and third-order nonlinear optical properties of 2-(4-chlorophenoxy)-N'-[(1E)-1-(4-methylphenyl) ethylidene] acetohydrazide

A new organic hydrazide derivative crystal, 2-(4-chlorophenoxy)-N′-[(1E)-1-(4-methylphenyl) ethylidene] acetohydrazide (4CP4MPEA) has been successfully synthesized and grown as single crystal from DMF solution. 4CP4MPEA crystallizes in triclinic crystal system with space group P-1 as revealed by single crystal X-ray diffraction (XRD). The molecule adopts an E configuration with respect to its CN double bond. The dihedral angle between the two phenyl rings is 79.29 (14)°. The synthesized compound has been characterized by UV/Vis and 1H NMR spectrum. Thermal properties and close contacts present in the crystal have also been investigated. The intermolecular interactions in the crystal structure were quantified and analyzed using Hirshfeld surface analysis. Open aperture Z-Scan data demonstrate the presence of two-photon absorption. Calculated values of σex and σg are 4.01 × 10−17cm2 and 1.33 × 10−21 cm2 respectively. The value of σex ≫> σg clearly indicates that the nonlinear absorption (NLA) process is due to the reverse saturable absorption (RSA). Observed optical limiting characteristics in 4CP4MPEA are attributed to the RSA. The Optical limiting threshold is found to be 3.13 × 1012 W/m2.

A simple and efficient method for the synthesis of 5,6-dihydropyrazin-2(1H)-one O-(tert-butyl)oximes, quinoxalin-2(1H)-one O-(tert-butyl)oximes and its derivatives

A simple and efficient method was developed for the synthesis of 5,6-dihydropyrazin-2(1H)-one O-(tert-butyl)oximes, quinoxalin-2(1H)-one O-(tert-butyl)oximes and its derivatives from N-tert-butoxy acyl imidoyl bromide and diamines. Twenty three novel compounds were readily synthesized using this procedure in excellent yields. The products possessed Z-stereochemistry with regard to the CN double bond. In these reactions, the amino group first attacked an imidoyl carbon of the N-tert-butoxy acyl imidoyl bromide in order to obtain the Z-intermediate; then another amino group attacked the carbonyl carbon of the intermediate. The rate of intramolecular cyclization of the intermediate was dependent on the position of the diamino groups.

Spectroscopic studies of aryl substituted 1-phenyl-2-pyrazolines: Steric and electronic substitution effects

A series of aryl substituted 1-phenyl-2-pyrazolines containing electron-donating and electron-withdrawing substituents on different positions of the C3 or C5-aryl groups were synthesized and their steric and electronic effects on characteristic spectral data were investigated by experimental spectroscopic methods (UV–Vis, IR and NMR) and DFT computations. Whereas the C5-aryl group of the heterocyclic ring behaves as σ-donor/acceptor substituent, the π-donor/acceptor ability of the C3-aryl group depends on the co-planarity of the substituent with the aryl ring and also the extent of the orientation of this C3-aryl ring towards the CN double bond of the heterocyclic ring. A significant through conjugation of the lone pair on the N1-atom towards the C3-aryl ring is observed when the electron-withdrawing nitro group is located on the para-position of this aryl ring. The experimental spectroscopic results for the substitution effects are also supported by (TD)DFT/6-311++G(d,p) computed UV–Vis spectra. Experimental and theoretical NMR chemical shifts and spin-spin coupling constants obtained for these 2-pyrazolines validated by Karplus diagram approves the structures predicted for these compounds.

Alternative mechanisms of thermal decomposition of o-nitrotoluene in the gas phase

The density functional theory methods were used to demonstrate that during the thermal decomposition of o-nitrotoluene, with the formation of 5-methylene-6-aci-nitrocyclohexa- 1,3-diene (aci-form) being the primary event, the rotation of the =N(O)OH group around the CN double bond in the aci-form is of key importance. The activation enthalpy is lower for this step than for the alternative process of H atom transfer between the O atoms in this group. This accounts for the competitive formation of the experimentally observed products of о-nitrotoluene thermal decomposition, namely, the hydroxyl radical and water. The activation barriers of the reactions were estimated over a broad temperature range, which indicated the possible contribution of о-nitrotoluene thermal decomposition and other alternative primary event mechanisms (nitro—nitrite rearrangement, bicyclization) to the efficient rate constant. The results account for the differences between the activation parameters experimentally determined at various temperatures by different authors.

Synthesis of a C3-symmetric tris-imine via dynamic covalent bond formation between a trialdehyde and a triamine

Dynamic covalent chemistry is an effective technique for the preparation of complex organic compounds. We succeeded in synthesizing a cage-shaped compound through the aggregation of two types of functional molecules. More specifically, a tris-imine 5 was quantitatively obtained by reacting a C3-symmetric trialdehyde 1 with a triamine 4 in acetonitrile in the presence of a trifluoroacetic acid catalyst. We also achieved the synthesis of the corresponding triamine 9 and the acetylated derivative 10 through reduction of the tris-imine CN double bonds and subsequent acetylation.

Synthesis, crystal structure and 3D-QSAR studies of antifungal (bis-)1,2,4-triazole Mannich bases containing furyl and substituted piperazine moieties

A series of novel title compounds 6a-6r and 7a-7c have been synthesized by Mannich reaction of the new triazole Schiff base intermidiates, substituted piperazine and formaldehyde under mild conditions in excellent yields. The crystal structure of compound 6i was determined to show a chair conformation of the piperazine ring and an (E)-configuration of the CN double bond. The bioassay results indicated that most of the newly synthesized compounds exhibited excellent in vitro inhibitory activities and broader spectrum against several plant fungi, and were more effective than the control Triadimefon. Several compounds also displayed favourable in vivo antifungal activities. The relationships between the compound structures and various biological activities were discussed. Furthermore, the CoMFA calculation based on the antifungal activity data of compounds 6 against R. cerealis was carried out to establish a 3D-QSAR model, which revealed that steric and electrostatic fields were two most important factors for contributing the bioactivity of the compounds. The present work will provide significant information for guiding optimization of such new structures to develop novel agrochemicals with higher antifungal activities.