Electron-rich Groups Research Articles

Extra precision glide docking, free energy calculation and molecular dynamics studies of 1,2-diarylethane derivatives as potent urease inhibitors

For the latter half of the twentieth century, most medical professionals considered bacterial infection to be a primary cause of gastrointestinal ulcers in human beings. In 1994, the World Health Organization (WHO) recognized Helicobacter pylori, the bacterium most closely linked to ulcer development, as a type I carcinogen. Biological research has shown that there is a positive correlation between the number of species in the Helicobacter genus and the number of medical conditions associated with Helicobacter infection, both of which are increasing rapidly. N-Benzylaniline derivatives, frequently used in industrial manufacturing, are being considered as a strong candidate for ongoing drug modeling in search of novel therapies. The basic goal behind this study was to determine the potency of experimentally proved data, and to determine favorable substituents to enhance potency, and thereafter to support this finding through theoretical modification of the existing base skeleton by addition of suitable substituents. Ligands were investigated thoroughly by paying attention to the urease-inhibitory properties present in the selected series. Initially, docking was performed on ligands with protein to produce efficient docking poses. Molecular dynamics (MD) simulations were also performed to precisely understand the interactions between ligands and proteins. Thereafter, MM-GBSA was used in order to validate the methods and results. Good interaction was observed with amino acids Arg338, Ala169, Asp223, His322, and Asn168. This study also revealed that the electron rich hydroxyl group (-OH) substituent plays an important role during bond formation. In addition, various hydrogen bonds, ionic bonds, and pi-pi stacking bonds make significant contributions towards urease inhibition. Therefore, further research utilizing electron-rich moieties may lead to novel and efficacious urease inhibitors.

Glutathione sensing mechanism of a fluorescent probe: Excited state intramolecular proton transfer and photoinduced electron transfer

In this work, the fluorescence turn-on mechanism of glutathione probe azido-substituted 2-(2′-hydroxyphenyl)benzoxazole derivative (AHBO) has been thoroughly studied based on the density functional theory and time-dependent density functional theory methods. The constructed potential energy curves demonstrate that the proton transfer (PT) processes of the probe AHBO and the final product AHBOG after the glutathione-azide reaction are more likely to occur in the first excited state than in the ground state. Results of frontier molecular orbital analyses show that the S1 state of AHBO is a complete charge-separation state, and the non-radiative acceptor-excited photoinduced electron transfer (a-PET, fluorophore as the electron acceptor) from the excited azide group to the 2-(2′-hydroxyphenyl)benzoxazole (HBO) would take place upon photoexcitation, which is responsible for the fluorescence quenching of the probe AHBO. Whereas, without the electron-rich azide group, the product AHBOG undergoes the excited state intramolecular proton transfer (ESIPT) in conjunction with the weak intramolecular charge transfer (ICT) process in the S1 state. The absence of the a-PET and the two processes mentioned above provide explanations for the fluorescent enhancement observed with the product AHBOG.

Colorimetric paper sensor for sensitive detection of explosive nitroaromatics based on Au@Ag nanoparticles

Rapid, reliable, onsite approaches for detection trace level of trinitrotoluene (TNT) is a pressing necessity for both homeland security and environmental protection. To this end, hydrophilic amine(-NH2) protected Au@Ag nanoparticles (NPs) were developed and fabricated as colorimetric paper sensor for delicate detection of TNT. The as-developed nanoprobe selectively reacts with TNT through classic Meisenheimer complex formation by means of charge transfer process from an electron-rich NH2 group of β-cysteamine to an electron-deficient nitro group on TNT. Due to the absence of this particular interaction of other nitroaromatics, the proposed probe is highly selective for TNT detection with a better linear range (0–20 μg/mL) and limit of detection (LOD) of 0.35 μg/mL. The present work provides a novel and facile strategy to fabricate colorimetric paper sensors with rapid and selective recognition ability for label free analysis of TNT.

Electron-rich functional doping carbon host as dendrite-free lithium metal anode

The Li metal anode has been regarded as the ultimate anode because of high theoretical capacity and low potential. Unfortunately, dendrite growth and safety issues impede its practical applications. Herein, we report a series of electron-rich functional groups, such as nitrogen, oxygen and phosphorus, doped Ketjen Black (ECP) as a lithium deposition/dissolution host. The electron-rich functional groups can effectively improve the wettability and lithiophility of the carbon host, which is benefit to induce homogeneous lithium deposition in the Ketjen Black (ECP), rendering significant inhibition of dendrite growth and effective improvement of electrochemical stability. Under the roles of these factors, the nitrogen doped Ketjen Black (ECP) electrode achieves a high Coulombic efficiency of 97.8% over 300 cycles at 1.0 mA cm−2, while the pristine ECP electrode only maintains 110 cycles. What's more the O-doped ECP and P-ECP electrode also keeps longer cycles than the pristine ECP electrode.

Hierarchical porous PANI/MIL-101 nanocomposites based solid-state flexible supercapacitor

Metal-Organic Frameworks (MOFs) have attracted increasing attention in the field of energy storage owing to their high porosity, high specific surface area, high charge storage. However, the poor conductivity in most MOFs largely hinders their electrical properties. In this work, we developed an effective strategy to grow the conductive polyaniline (PANI) inside the pores of MIL-101 (labeled as PANI/MIL-101) to form a fixed interpenetrating network structure. The electron-rich imine group in PANI is chelated with the coordinatively unsaturated metal sites (CUS) in MIL-101 to form a relatively strong bonded complex and through other synergistic effects to enhance the conductivity and electrochemical properties. The resultant PANI/MIL-101 exhibited a superior high capacitance of 1197 F g−1 (i.e., 957.6C g−1) at 1 A g−1 in constant current charge and discharge test. The assembled flexible solid-state supercapacitor showed a favorable specific capacitance, power density and good cycling stability (a 81% capacitance retention rate over 10,000 cycles). It also demonstrates a good flexibility, as evidenced by a small capacitance loss of 10% after being subject to 1000 bending cycles at 180°. The PANI/MIL-101 nanocomposite showed great potential in energy storage device.

A selective removal of the secondary hydroxy group from ortho-dithioacetal-substituted diarylmethanols.

We present a successful deoxygenation reaction of ortho-1,3-dithianylaryl(aryl)methanols which enables a selective removal of the secondary hydroxy group in presence of the 1,3-dithianyl moiety under reductive conditions. This reaction proceeds well with ZnI2/Na(CN)BH3 in dichloroethane or benzene for both unsubstituted and substituted aryls (by electron-rich groups). This is leading to formyl-protected diarylmethanes with potential application in the synthesis of new pharmaceuticals and optoelectronic materials. This synthetic approach gives an access to a wide variety of functionalized ortho-1,3-dithianylaryl(aryl)methanes in 26–95% yields and is recommended for the substrates containing sulfur atoms, for which transition metal-induced reactions fail.

Immobilization of thiol-functionalized ionic liquids onto the surface of MIL-101(Cr) frameworks by S[sbnd]Cr coordination bond for biodiesel production

A novel functionalized MOF heterogeneous catalyst (MIL-101(Cr) @MBIAILs), 2-Mercaptobenzimidazole ILs with electron-rich SH groups immobilized onto the surface of the well-defined MIL-101(Cr) frameworks, was constructed and fabricated by the SCr coordination bond on the basis of the facile post-synthetic modification strategy. The heterogeneous catalyst was measured by XRD, FTIR, SEM, TEM, TGA, EA and N2 adsorption–desorption, and the catalytic behavior of the catalyst was assessed by the esterification about oleic acid and methanol as a model reaction. The results showed that MBIAILs have been successfully immobilized onto the surface of MIL-101(Cr) frameworks by SCr coordinate bonds. More importantly, the conversion of oleic acid just decreased from 91.0% to 82.1% when the catalyst had been reused six times. This exhibited the prepared catalyst had superior catalytic behavior and excellent reusability.

Aggregation-Induced Long-Lived Phosphorescence in Nonconjugated Polyurethane Derivatives at 77 K

Achieving long-persistent phosphorescence in polymers is a challenge even at low temperatures. In this work, long-persistent phosphorescence (>1 s) is observed in nonconjugated polyurethane derivatives at 77 K, which is among the longest reported phosphorescent lifetimes for an organic polymer. The mechanism for this unusual behavior has been shown by steady-state photophysical characterization and time-resolved emission spectra to arise from the formation of intra- and/or intermolecular carbonyl clusters at low temperature. The lifetime of long-persistent phosphorescence is increased by the introduction of an aromatic monomer into the nonconjugated polyurethane chains. This is attributed to intra- and/or intermolecular n−π* transitions from electron-rich carbonyl groups to the conjugated aromatic units, thereby enhancing the intersystem crossing rate. Coating an ultraviolet InGaAsN light-emitting diode with a polyurethane derivative as the emitter gives cryogenic afterglow with long-persistent phosphores...

Lewis Base/Bronsted Acid Dual-Catalytic C-H Sulfenylation of Aromatics.

A Lewis base/Bronsted acid catalyzed aromatic sulfenylation is reported. These studies demonstrated that the incorporation of electron-rich sulfenyl groups proceeded in the absence of a Lewis base, with kinetic studies indicating an autocatalytic mechanism. The incorporation of electron-poor sulfenyl groups demonstrated little autocatalysis necessitating the use of a Lewis base. This method proved amenable to diverse arenes and heterocycles and was effective in the context of the late-stage functionalization of biologically active small molecules.

Imide arylation with aryl(TMP)iodonium tosylates.

Herein, we describe the synthesis of N-aryl phthalimides by metal-free coupling of potassium phthalimide with unsymmetrical aryl(TMP)iodonium tosylate salts. The aryl transfer from the iodonium moiety occurs under electronic control with the electron-rich trimethoxyphenyl group acting as a competent dummy ligand. The yields of N-aryl phthalimides are moderate to high and the coupling reaction is compatible with electron-deficient and sterically encumbered aryl groups.

Ask Not How Many, But Where They Are: Substituents Control Energetic Ordering of Frontier Orbitals/Electronic Structures in Isomeric Methoxy-Substituted Dibenzochrysenes

Redox properties of polycyclic aromatic hydrocarbons (PAHs) can be modulated by substitution with electron-rich groups. Here we show, using the example of dibenzo[g,p]chrysene (DBC), that substitution position (i.e., meta vs para) alters the energetic ordering of frontier molecular orbitals (FMOs), leading to cation radicals with altered electronic structures and thereby redox/optical properties. In particular, incorporation of four methoxy groups in parent DBC at meta positions similarly impacts the energies of phenanthrene-like HOMO and biphenyl-like HOMO-1, while their incorporation at para position swaps energetic ordering of HOMO and HOMO-1. We demonstrate that a straightforward analysis of FMOs provides valuable insight toward the rational design of novel PAHs with tailored redox properties.

Ice-like Cyclic Water Hexamer Trapped within a Halide Encapsulated Hexameric Neutral Receptor Core: First Crystallographic Evidence of a Water Cluster Confined within a Receptor-Anion Capsular Assembly

Over the past few decades, the tren [tris(2-aminoethyl)amine] skeleton has materialized as one of the supreme anion binding building blocks demonstrating a strong interplay among topology, complementarity, cooperativity, and coordination. However, anion recognition by modest tren-based unsubstituted aromatic urea has been underexplored, mainly due to the deficiency of π-acidic or electron-withdrawing aryl terminals. This report establishes an infrequent hexameric neutral receptor-anion-water molecular self-assembly, where a conformationally flexible C3v-symmetric halide (F–/Cl–) encapsulated electron-rich naphthyl group containing N-bridged tripodal urea receptor effectively entraps a chair-shaped ice-like neutral cyclic water hexamer within the hexameric cavity of a neutral receptor-halide host–guest assembly.

MPA-capped CdSe QD/mercaptoethylamine-capped AuNP nanocomposite-based sensor for instant detection of trinitrotoluene

CdSe quantum dots capped with mercaptopropionic acid (CdSe@MPA QDs) were synthesized by chemical route method. The developed CdSe@MPA QDs were pH optimized for higher emission. Gold nanoparticles in aqueous dispersion medium were synthesized by using sodium citrate as reduction agent and capped with mercaptoethylamine (MEA). Further, AuNP-MEA nanoparticles were conjugated with CdSe@MPAQDs. The “as-synthesized” nanomaterials and their composites were characterized by different analytical techniques like TEM, DLS, FTIR, UV-Vis, and PL spectroscopy. Upon excitation at λex = 400 nm, CdSe@MPA QDs show emission at 540 nm (λem) leading in a good spectral overlap with absorption spectra of AuNPs (λmax = 521 nm). Trinitrotoluene (TNT), being an electron deficient species can easily bind with electron-rich amine group. The amine functionalized GNPs (AuNP@MEA) were used as quenchers for FRET between QDs and GNPs to detect TNT. Using this assay, TNT has been selectively detected up to 21.9 nmol L−1 (LOD). Schematic diagram showing TNT detection based on FRET between gold nanoparticles and quantum dots is also suggested.

Sensitive detection of pesticides by a highly luminescent metal-organic framework

This work reports a highly luminescent metal-organic framework (MOF) with high surface area of 4073.9 m2 g−1, exhibiting an excellent adsorption ability and sensing performance in rapidly detecting parathion-methyl. This is an excellent example of luminescent MOFs to sensitively detect pesticides by fluorescent quenching with satisfactory results. This sensor provides a very wide linear detection range from 1.0 μg kg−1 to 10 mg kg−1, and low limit of detection 0.12 μg kg−1 (0.456 nM) for parathion-methyl. This low detection limit is much lower than the maximum residue limits (MRL) in the European Union pesticides database (0.01 mg kg−1 for fruits and vegetables, 0.02 mg kg−1 for tree nuts), as well as those of previous assays. The quenching effect of parathion-methyl is attributed to the electron-rich chemical group of nitroaromatics which might lead to photo-induced electron transfer. The fluorescent method has been reliably used for the determination of parathion-methyl in spiked irrigation water with satisfactory results, which suggests its potential for rapid detection of pesticides in food and environmental sample.

DFT investigation on the adsorption of munition compounds on α-Fe2O3: similarity and differences with α-Al2O3.

Arid environments have long been a testing and training ground for novel munitions. However, these activities leave behind unknown quantities of munition residues with unknown impact on local flora and fauna. In particular, arid soil contains Lewis acidic metal oxides which bind and catalyze the electron rich substituent groups commonly found in munition compounds, although the exact mechanisms are poorly understood. The current study remedies this lack of knowledge by utilizing density functional theory (DFT) to explore various orientations of four important munition compounds on the α-Fe2O3(0001) and α-Al2O3(0001) surfaces. Our findings reveal that while α-Fe2O3 binds the munition compounds more strongly than α-Al2O3, all four compounds experienced elongation of their nitro (-NO2) groups, indicating their susceptibility towards degradation on these surfaces.

Interaction between functionalized graphene and sulfur compounds in a lithium-sulfur battery - a density functional theory investigation.

Lithium–sulfur (Li–S) batteries are emerging as one of the promising candidates for next generation rechargeable batteries. However, dissolution of lithium polysulfides in the liquid electrolyte, low electrical conductivity of sulfur and large volume change during electrochemical cycling are the main technical challenges for practical applications. In this study, a systematic first-principles density functional theory calculation is adopted to understand the interactions between graphene and graphene with oxygen containing functional groups (hydroxyl, epoxy and carboxyl groups) and sulphur (S8) and long chain lithium polysulfides (Li2S8 and Li2S4). We find the adsorption is dominated by different mechanisms in sulphur and lithium polysulfides, i.e. van der Waals attraction and formation of coordinate covalent Li–O bonds. The adsorption strength is dependent on the inter-layer distance and electron rich functional groups. Through these mechanisms, sulphur and lithium polysulfides can be successfully retained in porous graphene, leading to improved conductivity and charge transfer in the cathode of Li–S batteries.

A robust network binder with dual functions of Cu2+ions as ionic crosslinking and chemical binding agents for highly stable Li–S batteries

Polysulfides are immobilized not only by electron-rich functional groups through coordination interaction but also by cations through electrostatic attraction.

Efficient synthesis of esters through oxone-catalyzed dehydrogenation of carboxylic acids and alcohols.

Since esters are important organic synthesis intermediates, an environmentally friendly oxone catalyzed-esterification of carboxylic acids with alcohols has been developed. A series of carboxylic acid esters are obtained in high yield. This strategy requires mild reaction conditions, providing an attractive alternative for the construction of valuable carbonyl esters. Electron-rich and electron-deficient groups are compatible with the standard conditions and a variety of substrates are demonstrated. Moreover, the reaction could easily be adapted to typical prodrugs, drugs and gram-scale synthesis.

Computational investigations of intermolecular interactions between electron-accepting bromo- and iodo-pentafluorobenzene and electron-donating furan and thiophene

C6F5X (X = Br, I) exhibits intriguing σ- and π-hole characters, which enable it to accept electrons from the electron-rich atoms or groups in C4H4O and C4H4S via various intermolecular interactions.

Chemoselective Aliphatic C-H Bond Oxidation Enabled by Polarity Reversal.

Methods for selective oxidation of aliphatic C–H bonds are called on to revolutionize organic synthesis by providing novel and more efficient paths. Realization of this goal requires the discovery of mechanisms that can alter in a predictable manner the innate reactivity of these bonds. Ideally, these mechanisms need to make oxidation of aliphatic C–H bonds, which are recognized as relatively inert, compatible with the presence of electron rich functional groups that are highly susceptible to oxidation. Furthermore, predictable modification of the relative reactivity of different C–H bonds within a molecule would enable rapid diversification of the resulting oxidation products. Herein we show that by engaging in hydrogen bonding, fluorinated alcohols exert a polarity reversal on electron rich functional groups, directing iron and manganese catalyzed oxidation toward a priori stronger and unactivated C–H bonds. As a result, selective hydroxylation of methylenic sites in hydrocarbons and remote aliphatic C–H oxidation of otherwise sensitive alcohol, ether, amide, and amine substrates is achieved employing aqueous hydrogen peroxide as oxidant. Oxidations occur in a predictable manner, with outstanding levels of product chemoselectivity, preserving the first-formed hydroxylation product, thus representing an extremely valuable tool for synthetic planning and development.