Nitrophenyl Group Research Articles

3-Bromomethyl-4-methoxy-2-(2-nitrophenyl)-9-phenylsulfonyl-9H-carbazole

In the title compound, C26H19BrN2O5S, the carbazole tricycle is essentially planar, with the largest deviation being 0.126 (3) Å for the C atom connected to the nitro­phenyl group. The carbazole moiety is almost orthogonal to the benzene rings of the adjacent phenyl­sulfonyl and nitro­phenyl groups, making dihedral angles of 85.43 (15) and 88.62 (12)°, respectively. The mol­ecular conformation is stabilized by two C—H⋯O hydrogen bonds involving the sulfone group, which form similar six-membered rings. In the crystal, mol­ecules symmetrically related by a glide plane are linked in C(6) chains parallel to [001] by C—H⋯O hydrogen bonds formed with the participation of the nitro group. The chains are reinforced by additional C—H⋯π inter­actions.

Invited Presentation: Covalent Functionalization of Carbon Nanotubes and Graphene: Chemistry, Electronic Structure and Physical Properties

We have demonstrated the covalent functionalization of carbon nanotubes and graphene with a variety of chemistries including the use of nitrophenyl groups, Diels-Alder reactions and organometallic derivatization. The chemical formation of covalent carbon-carbon bonds involving the basal plane carbon atoms modifies the electronic properties of graphene; the transformation of the carbon centers from sp2 to sp3 introduces a barrier to electron flow by saturating the carbon atoms and opening a band gap which potentially allows the generation of insulating and semiconducting regions in graphene wafers. In this talk I will discuss our recent results on the electronic and magnetic properties of chemically modified graphene, the observation of ferromagnetism, and the application of organometallic chemistry to facilitate the interconnection of single-walled carbon nanotubes.

Hierarchical Nanocomposites of Polyaniline Nanowire Arrays on Reduced Graphene Oxide Sheets for Supercapacitors

Here we reported a novel route to synthesize a hierarchical nanocomposite (PANI-frGO) of polyaniline (PANI) nanowire arrays covalently bonded on reduced graphene oxide (rGO). In this strategy, nitrophenyl groups were initially grafted on rGO via C-C bond, and then reduced to aminophenyl to act as anchor sites for the growth of PANI arrays on rGO. The functionalized process was confirmed by atomic force microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy and thermogravimetric analysis. The electrochemical properties of the PANI-frGO as supercapacitor materials were investigated. The PANI-frGO nanocomposites showed high capacitance of 590 F g−1 at 0.1 A g−1, and had no loss of capacitance after 200 cycles at 2 A g−1. The improved electrochemical performance suggests promising application of the PANI-frGO nanocomposites in high-performance supercapacitors.

Prussian blue nanocubes on nitrobenzene-functionalized reduced graphene oxide and its application for H2O2 biosensing

Detection of H2O2 is very important in biological analysis, clinical diagnosis, food industry, etc. This work presents an electrochemical approach for the detection of H2O2 based on Prussian blue (PB) nanocubes-nitrobenzene-reduced graphene oxide (RGO) nanocomposites (PB nanocubes-nitrobenzene-RGO). The hybrid nanocomposites were constructed by growing PB nanocubes onto the nitrobenzene-RGO composites which were prepared by spontaneous grafting nitrophenyl groups to the basal carbon atoms of RGO based on chemical bonding. The obtained PB nanocubes-nitrobenzene-RGO nanocomposites were characterized by scanning electron microscopy, X-ray diffraction and Fourier transform infrared spectroscopy. The formation mechanism of PB nanocubes-nitrobenzene-RGO nanocomposites was investigated and discussed in detail. The PB nanocubes-nitrobenzene-RGO modified glassy carbon electrode shows good electrocatalysis toward the reduction of H2O2. The resulted H2O2 biosensor exhibited a rapid response of 2s, a low detection limit of 0.4μM, a wide linear range of 1.2μM to 15.25mM and high sensitivity of 300.16μAcm−2mM−1, as well as good stability, repeatability and selectivity. Further immobilizing glucose oxidase on the PB nanocubes-nitrobenzene-RGO nanocomposites/GCE, an amperometric glucose biosensor was achieved by monitoring the generated H2O2 under a relatively negative potential. The sensors might be used as a promising one for practical application.

Coating of gold substrates with polyaniline through electrografting of aryl diazonium salts

The results of an experimental study on electrochemical preparation of polyaniline (PANI)/polycrystalline gold composites are reported in this work. A three steps approach is adopted in order to obtain a stable and uniform coating: (1) functionalization of the gold surface by 4-nitrophenyl group, (2) electrochemical reduction of the nitro group to amine, and (3) electropolymerization of aniline onto the surface of the aminophenyl-modified gold electrode. Cyclic voltammetries and electrochemical impedance spectroscopies are used to characterize the gold surface after each step. Also the results of a sample prepared by electropolymerization of PANI on bare gold are presented as a comparison.

On the Addition of Aryl Radicals to Graphene: The Importance of Nonbonded Interactions

Dispersion-corrected density functional theory is utilized to study the addition of aryl radicals to perfect and defective graphene. Although the perfect sheet shows a low reactivity against aryl diazonium salts, the agglomeration of these groups and the addition onto defect sites improves the feasibility of the reaction by increasing binding energies per aryl group up to 27 kcal mol(-1). It is found that if a single phenyl radical interacts with graphene, the covalent and noncovalent additions have similar binding energies, but in the particular case of the nitrophenyl group, the adsorption is stronger than the chemisorption. The single vacancy shows the largest reactivity, increasing the binding energy per aryl group by about 80 kcal mol(-1). The zigzag edge ranks second, enhancing the reactivity 5.4 times with respect to the perfect sheet. The less reactive defect site is the Stone-Wales type, but even in this case the addition of an isolated aryl radical is exergonic. The arylation process is favored if the groups are attached nearby and on different sublattices. This is particularly true for the ortho and para positions. However, the enhancement of the binding energies decreases quickly if the distance between the two aryl radicals is increased, thereby making the addition on the perfect sheet difficult. A bandgap of 1-2 eV can be opened on functionalization of the graphene sheets with aryl radicals, but for certain configurations the sheet can maintain its semimetallic character even if there is one aryl radical per eight carbon atoms. At the highest level of functionalization achieved, that is, one aryl group per five carbon atoms, the bandgap is 1.9 eV. Regarding the effect of using aryl groups with different substituents, it is found that they all induce the same bandgap and thus the presence of NO(2), H, or Br is not relevant for the alteration of the electronic properties. Finally, it is observed that the presence of tetrafluoroborate can induce metallic character in graphene.

Excited state dynamics of a push–pull stilbene: A femtosecond transient absorption spectroscopic study

Abstract The excited state dynamics of a structurally flexible push–pull stilbene, namely, trans -4-(N,N-dimethylamino)-4′-nitrostilbene (DMANS), in solvents of varying polarities, H-bonding abilities and viscosities, has been investigated using femtosecond transient absorption spectroscopic technique. Results of DFT and TDDFT calculations have been used to explain the experimental data. Following photoexcitation of the planar DMANS molecule to the excited singlet (S 1 ) state, it undergoes cis–trans isomerization via twisting of the double bond. However, in solvents of medium and large polarities, the twisted intramolecular charge transfer (TICT) process involving only the rotation of the nitrophenyl group, but not the rotation of the dimethyl aniline or nitro group, is the dominant relaxation process in the excited state of DMANS, in polar solvents.

Colorimetric macrocyclic anion probes bearing nitrophenylurea and nitrophenylthiourea binding groups

Two novel molecular probes bearing two urea (sensor 1) or thiourea (sensor 2) groups (as anion recognition site) coupled with a nitrophenyl group (chromogenic unit) were synthesized and evaluated according to the binding site-signaling subunit approach.The behavior of these different compounds toward metal ions (Co2+, Ni2+, Cu2+, Zn2+, and Cd2+) and anions (F−, Cl−, Br−, I−, ClO4−, NO3−, CN−, OH−, CH3COO−, and H2PO4−) was investigated by UV–vis spectroscopy in DMSO.

Formation of a Bifunctional Redox System Using Electrochemical Reduction of Platinum in Ferrocene Based Ionic Liquid and Its Reactivity with Aryldiazonium

The electrochemical reduction of platinum in ferrocene based ionic liquid, 1-ferrocenylethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([FcEMIM][TFSI]), has been investigated on both macro and micro platinum electrodes. The electrochemical and X-ray photoelectron spectroscopy (XPS) analyses of the reduced platinum evidence the presence and the intercalation of the ferrocene imidazolium into the platinum surface. The resulting metal-organic phase was anticipated to be of the general formula [Ptn(δ-), FcEMIM(δ+)]. Next, the spontaneous reaction of the electrogenerated Pt phases as reducing agent with phenyl diazonium salts was performed. The "reduced platinum phase" reacts with nitrophenyl diazonium salts, without applying any external potential, and conduces to the attachment of nitrophenyl groups onto the surface. Detailed experiments based on cyclic voltammetry and XPS were carried out to follow the occurrence of the grafting. Indeed, both experiments evidence the presence of ferrocene and nitrophenyl groups on the Pt surface. As a result, a bifunctional active surface containing two redox systems has been obtained.

Mixed Monolayer Organic Films via Sequential Electrografting from Aryldiazonium Ion and Arylhydrazine Solutions

Sequential electrografting at glassy carbon from aryldiazonium salt solutions, or an aryldiazonium salt followed by an arylhydrazine, leads to the formation of covalently attached monolayer films incorporating two modifiers. In the first step, a 4-((triisopropylsilyl)ethynyl)phenyl film is electrografted to the surface, followed by removal of the triisopropylsilyl group to give a submonolayer of phenylethynylene groups. Two general strategies can then be applied to "fill in" the sparse monolayer with a second modifier. In the first route, nitrophenyl groups are grafted to the phenylethynylene-modified surface by the oxidation of 4-nitrophenylhydrazine. Ferrocene can be coupled to the terminal alkyne groups on the surface via a click reaction with azidomethylferrocene; an electrochemical measurement of the amount of immobilized ferrocene demonstrates that the phenylethynylene layer retains close to full reactivity after the second grafting step. In the alternative strategy, ferrocene is coupled to the phenylethynylene layer prior to grafting nitrophenyl groups by the reduction of the 4-nitrobenzenediazonium ion or by the oxidation of 4-nitrophenylhydrazine. For all approaches, the optimization of the grafting conditions gives surface concentrations of ferrocene and nitrophenyl groups that are consistent with those of a mixed monolayer. The stepwise generation of mixed monolayers is also monitored by film thickness measurements by depth profiling using the atomic force microscope. Thickness values are consistent with the proposed film structure in each preparation step.

Diazonium Functionalized Graphene: Microstructure, Electric, and Magnetic Properties

The unique honeycomb lattice structure of graphene gives rise to its outstanding electronic properties such as ultrahigh carrier mobility, ballistic transport, and more. However, a crucial obstacle to its use in the electronics industry is its lack of an energy bandgap. A covalent chemistry strategy could overcome this problem, and would have the benefits of being highly controllable and stable in the ambient environment. One possible approach is aryl diazonium functionalization. In this Account, we investigate the micromolecular/lattice structure, electronic structure, and electron-transport properties of nitrophenyl-diazonium-functionalized graphene. We find that nitrophenyl groups mainly adopt random and inhomogeneous configurations on the graphene basal plane, and that their bonding with graphene carbon atoms leads to slight elongation of the graphene lattice spacing. By contrast, hydrogenated graphene has a compressed lattice. Low levels of functionalization suppressed the electric conductivity of the resulting functionalized graphene, while highly functionalized graphene showed the opposite effect. This difference arises from the competition between the charge transfer effect and the scattering enhancement effect introduced by nitrophenyl groups bonding with graphene carbon atoms. Detailed electron transport measurements revealed that the nitrophenyl diazonium functionalization locally breaks the symmetry of graphene lattice, which leads to an increase in the density of state near the Fermi level, thus increasing the carrier density. On the other hand, the bonded nitrophenyl groups act as scattering centers, lowering the mean free path of the charge carriers and suppressing the carrier mobility. In rare cases, we observed ordered configurations of nitrophenyl groups in local domains on graphene flakes due to fluctuations in the reaction processes. We describe one example of such a superlattice, with a lattice constant nearly twice of that of pristine graphene. We performed comprehensive theoretical calculations to investigate the lattice and the electronic structure of the superlattice structure. Our results reveal that it is a thermodynamically stable, spin-polarized semiconductor with a bandgap of ∼0.5 eV. Our results demonstrate the possibility of controlling graphene's electronic properties using aryl diazonium functionalization. Asymmetric addition of aryl groups to different sublattices of graphene is a promising approach for producing ferromagnetic, semiconductive graphene, which will have broad applications in the electronic industry.

Spin‐Polarized Semiconductors: Tuning the Electronic Structure of Graphene by Introducing a Regular Pattern of sp3 Carbons on the Graphene Plane

First-principles calculations (generalized gradient approximation, density functional therory (DFT) with dispersion corrections, and DFT plus local atomic potential) are carried out on the stability and electronic structures of superlattice configurations of nitrophenyl diazonium functionalized graphene with different coverage. In the calculations, the stabilities of these structures are strengthened significantly since van der Waals interactions between nitrophenyl groups are taken into account. Furthermore, spin-polarized and wider-bandgap electronic structures are obtained when the nitrophenyl groups break the sublattice symmetry of the graphene. The unpaired quasi-localized p electrons are responsible for this itinerant magnetism. The results provide a novel approach to tune graphene's electronic structures as well as to form ferromagnetic semiconductive graphene.

Concise Syntheses, Polymers, and Properties of 3-Arylthieno[3,2-b]thiophenes

Thieno[3,2-b]thiophenes (TT), having para-substituted phenyl groups at C-3, have been synthesized through a ring closure reaction, using P4S10, in moderate to high yields. Their absorbance studies displayed that the TT, having nitrophenyl group had the most red shift absorbance at 365 nm, which also showed the lowest optical band gap of 2.92 eV; the rest of the TTs had the absorbance between 300 and 302 nm. Cyclic voltammetry studies indicated that while all the TTs had the oxidation potentials above 1.0 V, the TT with dimethylaminophenyl group had the lowest oxidation potential of 1.33 V. The rest had the oxidation potentials between 1.6 and 1.99 V. The TTs were both electropolymerized and copolymerized with thiophene through Suzuki coupling reaction. Electropolymerized polymers indicated that while the polymer having strong electron donating dimethylaminophenyl group had the lowest oxidation potential of 0.97 V, the rest of the polymers displayed the potentials between 1.09 and 1.39 V. Their electronic ...

Chemistry on Boranils: An Entry to Functionalized Fluorescent Dyes

A Boranil fluorophore bearing a nitro-phenyl group has been selectively reduced to its anilino form and then successfully converted to amide, imine, urea, and thiourea derivatives which are fluorescent dyes. Its isolated isothiocyanate intermediate derivative was used in a model labeling experiment with Bovine Serum Albumin (BSA). The purified labeled-BSA exhibits strong luminescence (Φ(f) = 47%) in a phosphate buffer at pH = 7.4.

Receptor-Based Detection of 2,4-Dinitrotoluene Using Modified Three-Dimensionally Ordered Macroporous Carbon Electrodes

Detection of explosives, such as 2,4,6-trinitrotoluene (TNT), is becoming increasingly important. Here, 2,4-dinitrotoluene (DNT, a common analogue of TNT) is detected electrochemically. A receptor based electrode for the detection of DNT was prepared by modifying the surface of the walls of three-dimensionally ordered macroporous (3DOM) carbon. Nitrophenyl groups were first attached by the electrochemical reduction of 4-nitrobenzenediazonium ions, followed by potentiostatic reduction to aminophenyl groups. Chemical functionalization reactions were then performed to synthesize the receptor, which contains two urea groups, and a terminal primary amine. Detection of DNT using cyclic voltammetry was impeded by a large background current that resulted from the capacitance of 3DOM carbon. Detection by square wave voltammetry eliminated the background current and improved the detection limit. Unfunctionalized 3DOM carbon electrodes showed no response to DNT, whereas the receptor-modified electrodes responded to DNT with a detection limit of 10 μM. Detection of DNT was possible even in the presence of interferents such as nitrobenzene.

A versatile route to modify polyethersulfone membranes by chemical reduction of aryldiazonium salts

Ultrafiltration polyethersulfone membranes were modified covalently by chemical reduction of aryl diazonium salts. Functionalizations were performed with four aryl diazonium salts bearing different functional groups (4-benzyltriphenylphosphonium diazonium, 4-nitrophenyl diazonium, 4-benzonitrile diazonium and 4-phenylacetic acid diazonium) so as to demonstrate the versatility of the method. The efficiency of the different functionalizations was checked with various characterization techniques. Attenuated total reflectance–Fourier transform infra red spectroscopy revealed the presence of 4-nitrophenyl, 4-benzonitrile and 4-phenylacetic acid groups at the surface of the different modified membranes but no characteristic vibration band was detected on the surface of the membrane modified with 4-benzyltriphenylphosphonium diazonium. The presence of 4-benzyltriphenylphosphonium, however, could be demonstrated by both Energy Dispersive X-ray spectroscopy (detection of the Kα ray of phosphorous at 2.015 keV) and streaming current measurements (shift of the membrane isoelectric point). Finally, dead-end filtration of an antibiotic (tylosin) was carried out with the unmodified membrane and the membrane modified by 4-benzyltriphenyl-phosphonium diazonium. Experiments revealed that the transport properties of the grafted membrane were significantly modified, with a significant increase in rejection mainly due to electrostatic repulsions between the surface of the modified membrane and tylosin.

Electrochemical immunosensor for the milk allergen β-lactoglobulin based on electrografting of organic film on graphene modified screen-printed carbon electrodes

A novel label-free voltammetric immunosensor for sensitive detection of β-lactoglobulin using graphene modified screen printed electrodes has been developed. The derivatization of the graphene electrode surface was achieved by electrochemical reduction of in situ generated 4-nitrophenyl diazonium cations in aqueous acidic solution, followed by electrochemical reduction of the terminal nitro groups to amines. The electrochemical modification protocol was optimized in order to generate monolayer of nitrophenyl groups on the graphene surface without complete passivation of the electrode. Unlike the reported method for graphene functionalization, we demonstrated here the ability of the electrografting of aryl diazonium salt to attach an organic film to the graphene surface in a controlled manner by choosing the suitable grafting protocol. Next, the amine groups on the graphene surface were activated using glutaraldehyde and used for the covalent immobilization of β-lactoglobulin antibodies. Cyclic and differential pulse voltammetry carried out in an aqueous solution containing [Fe(CN)6]3−/4− redox pair have been used for the immunosensor characterization. The results demonstrated that the DPV reduction peak current of [Fe(CN)6]3−/4− decreased linearly with increasing the concentration of β-lactoglobulin due to the formation of antibody–antigen complex on the modified electrode surface. The immunosensor obtained using this novel approach enabled a detection limit of 0.85pgmL−1 and a dynamic range from 1pgmL−1 to 100ngmL−1 of β-lactoglobulin in PBS buffer. In addition, the immunosensor evaluated in different samples including cake, cheese snacks, a sweet biscuit, showing excellent correlation with the results obtained from commercially enzyme-linked immunosorbent assay (ELISA) method.

Development of a Novel Optical Biosensor for Detection of Organophoshorus Pesticides Based on Methyl Parathion Hydrolase Immobilized by Metal-Chelate Affinity

We have developed a novel optical biosensor device using recombinant methyl parathion hydrolase (MPH) enzyme immobilized on agarose by metal-chelate affinity to detect organophosphorus (OP) compounds with a nitrophenyl group. The biosensor principle is based on the optical measurement of the product of OP catalysis by MPH (p-nitrophenol). Briefly, MPH containing six sequential histidines (6× His tag) at its N-terminal was bound to nitrilotriacetic acid (NTA) agarose with Ni ions, resulting in the flexible immobilization of the bio-reaction platform. The optical biosensing system consisted of two light-emitting diodes (LEDs) and one photodiode. The LED that emitted light at the wavelength of the maximum absorption for p-nitrophenol served as the signal light, while the other LED that showed no absorbance served as the reference light. The optical sensing system detected absorbance that was linearly correlated to methyl parathion (MP) concentration and the detection limit was estimated to be 4 μM. Sensor hysteresis was investigated and the results showed that at lower concentration range of MP the difference got from the opposite process curves was very small. With its easy immobilization of enzymes and simple design in structure, the system has the potential for development into a practical portable detector for field applications.

Spontaneous Grafting of Nitrophenyl Groups on Amorphous Carbon Thin Films: A Structure–Reactivity Investigation

Amorphous carbon materials find numerous applications in diverse areas ranging from implantable biodevices to electronics and catalysis. The spontaneous grafting of aryldiazonium salts is an important strategy for the modification of these materials, and it is widely used to display a range of functionalities or to provide anchoring groups for further functionalization. We have investigated the spontaneous attachment of 4-nitrobenzenediazonium salts from aqueous solutions onto amorphous carbon materials that differ in their sp2 content, with the aim of understanding to what extent bulk composition affects rates and yields of aryldiazonium adsorption at the carbon/solution interface. Amorphous carbons were deposited in the form of thin films via reactive magnetron sputtering and were characterized using a combination of Raman, infrared, UV–vis, and X-ray photoelectron spectroscopy to determine their sp2 content. Attenuated total internal reflection Fourier transform infrared spectroscopy (ATR-FTIR) was use...

Oroxylin A analogs exhibited strong inhibitory activities against iNOS-mediated nitric oxide (NO) production

A number of oroxylin A analogs were prepared and evaluated for their inhibitory activities against iNOS-mediated nitric oxide (NO) production from LPS-stimulated BV2 cells. The analogs were synthesized from purchased 2′-hydroxy-4,5,6-trimethoxyacetophenone and aldehydes in 3 steps. Among the tested compounds, several analogs (3b, 3c, 3d, 3f) exhibited strong inhibitory activities. Especially, the analog with 4-nitrophenyl group (3b) showed stronger inhibitory activity (IC50=4.73μM) than that of wogonin (IC50=7.80μM).