Electron-rich Groups Research Articles

Modular Synthesis of Diarylalkanes by Nickel-Catalyzed 1,1-Diarylation of Unactivated Terminal Alkenes

A nickel-catalyzed 1,1-diarylation of electronically unbiased alkenes has been developed, providing straightforward access to diarylalkanes from readily available materials. Importantly, both the e...

Engineering Lithium Ions Embedded in NiFe Layered Double Hydroxide Lattices To Activate Laminated Ni2+ Sites as High-Efficiency Oxygen Evolution Reaction Catalysts.

NiFe layered double hydroxides (LDHs) have been denoted as benchmark non-noble-metal electrocatalysts for the oxygen evolution reaction (OER). However, for laminates of NiFe LDHs, the edge sites are active, but the basal plane is inert, leading to underutilization as catalysts for the OER. Herein, for the first time, light and electron-deficient Li ions are intercalated into the basal plane of NiFe LDHs. The results of theoretical calculations and experiments both showed that electrons would be transferred from near Ni2+ to the surroundings of Li+ , resulting in electron-deficient properties of the Ni sites, which would function as "electron-hungry" sites, to enhance surface adsorption of electron-rich oxygen-containing groups, which would enhance the effective activity for the OER. As demonstrated by the catalytic performance, the Li-NiFe LDH electrodes showed an ultralow overpotential of only 298 mV at 50 mA cm-2 , which was lower than that of 347 mV for initial NiFe LDHs and lower than that of 373 mV for RuO2 . Reasonable intercalation adjustment effectively activates laminated Ni2+ sites and constructs the electron-deficient structure to enhance its electrocatalytic activity, which sheds light on the functional treatment of catalytic materials.

Modulating the Linker Immobilization Density on Aptameric Graphene Field Effect Transistors Using an Electric Field.

Aptameric graphene-based field-effect transistors (A-GFETs) always employ linkers, which could immobilize on graphene through π-π stacking between contained pyrenyl groups and graphene, to anchor aptamers. Aptamer density is closely associated with the A-GFET sensitivity and determined by the linker density. Using known linker immobilization methods, the linker density is random, uncontrollable, and limited. In this work, we propose a novel linker immobilization method which can be used to effectively modulate the linker density using an electric field and further bridge the relationship between the linker density and the A-GFET sensitivity. Here, polar molecule 1-pyrenebutanoic acid succinimidyl ester (PASE) is used as a linker representative. In the electric field, PASE is arranged regularly with the electron-rich pyrenyl group forced toward graphene in the solution due to electrostatic repulsion, thereby making it possible to modulate the quantity of PASE molecules that could interact with graphene by tuning the electric field application and then realizing the regulation of the A-GFET sensitivity. Experimental results indicate that the limits of detection (LODs) of A-GFETs for detecting interleukin-6 (IL-6) and insulin can be significantly improved to be 618 and 766 fM, respectively, by applying an electric field at -0.3 V for 3 h during PASE immobilization.

(Invited) Decapyrrylcorannulene Buckyhands

To mimic the smart molecular ‘hands’ for self-adaptably cradling various buckyballs in a (+)hand-ball-hand(-) mode, a decapyrrylcorannulene molecule having a concave corannulene and ten flexible electron-rich pyrryl groups has been synthesized by a facile metal-free catalytic Ullmann reaction under mild conditions. The usefulness of the as-synthesized Buckyhands was exemplified by crystallographic identification of tens buckyball structures representing pristine, exohedral, endohedral, dimeric and hetero-derivatization. The pyrryl groups twist with varying dihedral angles to adjust the interaction between decapyrrylcorannulene and fullerene, that is theoretically revealed to contribute more than the bowl-shaped palm of the corannulene in holding the buckyball structures.

Electrochemical Total Synthesis of Pratosine By Controlling for the Anodically Initiated One-/Two-Electron Transfer Process

Pratosine is a type of a pyrrolophenanthridone alkaloid that includes indole ring and electron donating group-substituted N-benzoyl moiety. Many researchers demonstrated various synthetic reactions to access a simple poly-heterocyclic structure of pyrrolophenanthridone. For instance, intramolecular cyclization between indoline and N-benzoyl moiety was accomplished by stoichiometric Pd-mediated C-H activation1, hypervalent iodine mediated oxidative cross-coupling2 and inverse electron-demand Diels-Alder reaction3. Continuously DDQ oxidation to convert indoline to indole is necessary in all case. We established electrochemical intramolecular radical cation cross-coupling and indole synthesis reaction. These reaction was initiated by same anodic oxidation for electron-rich benzoyl group, but acid or base additive-dependent different electron-transfer pathway was occurred in both cyclization and indole ring forming reaction.Reference(1) DC. Black, PA. Keller, N. Kumar, Tetrahedron Lett. 1989, 30, 5807-5808.(2) MD. Ganton, MA. Kerr, Org. Lett. 2005, 7, 4777-4779.(3) DL. Boger, SE. Wolkenberg, J. Org. Chem. 2000, 65, 9120-9124. Figure 1

Interaction of supported ionic liquids phases onto copper nanoparticles: A DFT study

The interaction between Supported Ionic Liquids Phases (SILPs) based on triazole and copper nanoparticles was investigated using density functional theory calculations. Three triazolium cations (T1+, T2+, and T3+) and four anions (I−, BF4−, PF6−, and NTf2−) were considered to form the Cu@SILP complexes. It is shown that the anion adsorption onto copper nanoparticles is favored compared to the cation adsorption. The Cu@SILP interaction is governed by coordinate covalent bonds, which can be modulated with chemical substitution on the triazole ring in the position of N1 and N3, including electron-rich groups. However, the stronger adsorption is observed for Cu@(I)SILP1 complex, which presents the more electron-rich triazole and the higher adsorption value of SILP onto Cu surface (5.18 eV). The surface modification allows us to change the properties of the complexes, where tuning properties using different anions generates a coarse change, while fine-tune can be achieved through chemical modification of a triazolium ring.

Light trapping induced flexible wrinkled nanocone SERS substrate for highly sensitive explosive detection

We reported an ultrasensitive TNT detection method via a novel light trapping induced wrinkled nanocone flexible SERS substrate, which was fabricated by colloidal lithography and oxygen plasma etching on transparent PET film. Especially, a set of nanowrinkles with 50−60 nm was found on the sidewall of nanocone after etching. By coating 30 nm gold film, this flexible SERS substrate provided uniform hot spots, which demonstrated high reproducibility and sensitivity. 4-ATP molecules based Meisenheimer complex, which is a well-known charge-transfer interaction between electron-poor TNT and electron-rich amino group, was taken to detect ultra-low concentration of TNT explosive. The Raman signal of TNT was significantly enhanced by charge-transfer, light trapping effect and coupled electromagnetic field. The detection sensitivity of TNT molecules was as low as 10−13mol/L, and show a good linear response in the range from 10−8 to 10−13mol/L. Consequently, by brushing this flexible SERS substrate onto a cloth bag, trace amount of TNT residues with concentration as low as 10-10mol/L can be easily analyzed. It is believed that the proposed highly sensitive and uniform flexible substrate provides a significant solution for trace analysis of TNT residue in criminal forensic, military and security check.

Platinum(II) coordination compound with 4′-[4-(dimethylamino)phenyl]-2,2′:6′,2″-terpyridine – The new insight into the luminescence behavior and substituent effect

{PtCl[4′-(4-NMe2)-Ph-terpy-κ3N]}BPh4·CH3CN (1) was synthesized and its structural, electrochemical and photophysical properties were characterized in comparison to previously described systems of [PtCl(4′-Ph-terpy-κ3N)]+ and [PtCl(4′-NMe2-terpy-κ3N)]+ to determine again the significance of the appropriate design of substituent in case of luminescence behavior of transition metal complex. The molecular formula of compound was confirmed by.X-ray analysis, elemental analysis, FT-IR and NMR studies. The geometries of ground and excited states of compound were also calculated on the basis of Density Functional Theory (DFT) method. The electrochemical properties were elucidated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The electronic absorption spectra of compound (1) in solutions are similar to those in described previously platinum(II) terpyridine coordination compounds. The photoluminescence properties were studied in various media to rationalize effects on emission properties caused by substituent, solvent polarity, concentration of solution and rigidity of media. The studied compound displays enhancement of photoluminescence properties in comparison to [PtCl(terpy-κ3N)]+ system, however its emission lifetime in the regard to [PtCl(4′-Ph-terpy-κ3N)]+ and [PtCl(4′-NMe2-terpy-κ3N)]+ is significantly decreased. This suggest the impeded charge transfer from electron-rich NMe2 group via phenylene bridge to the terpy core due to the unfavorable, inclined geometry of excited state. As a consequence of substituent twisting on the path S0 → S1 → T1, the interference of 3ILCT and 3MLCT excited state is disturbed favouring the non-radiative deactivation process of {PtCl[4′-(4-NMe2)-Ph-terpy-κ3N]}BPh4·CH3CN.

Cu(II) Ion Adsorption by Aniline Grafted Chitosan and Its Responsive Fluorescence Properties.

The detection and removal of heavy metal species in aquatic environments is of continued interest to address ongoing efforts in water security. This study was focused on the preparation and characterization of aniline grafted chitosan (CS-Ac-An), and evaluation of its adsorption properties with Cu(II) under variable conditions. Materials characterization provides support for the grafting of aniline onto chitosan, where the kinetic and thermodynamic adsorption properties reveal a notably greater uptake (>20-fold) of Cu(II) relative to chitosan, where the adsorption capacity (Qm) of CS-Ac-An was 106.6 mg/g. Adsorbent regeneration was demonstrated over multiple adsorption-desorption cycles with good uptake efficiency. CS-Ac-An has a strong fluorescence emission that undergoes prominent quenching at part per billion levels in aqueous solution. The quenching process displays a linear response over variable Cu(II) concentration (0.05–5 mM) that affords reliable detection of low level Cu(II) levels by an in situ “turn-off” process. The tweezer-like chelation properties of CS-Ac-An with Cu(II) was characterized by complementary spectroscopic methods: IR, NMR, X-ray photoelectron (XPS), and scanning electron microscopy (SEM). The role of synergistic effects are inferred among two types of active adsorption sites: electron rich arene rings and amine groups of chitosan with Cu(II) species to afford a tweezer-like binding modality.

Multifunctional Cellulose Nanocrystals as a High-Efficient Polysulfide Stopper for Practical Li-S Batteries.

Because of the severe shuttle effect of polysulfides, achieving durable Li-S batteries is still a great challenge, especially under practical operation conditions including the high sulfur content, high loading, and high operation temperature. Herein, for the first time, low-cost, eco-friendly, and hydrophilic cellulose nanocrystals (CNCs) are proposed as a multifunctional polysulfide stopper for Li-S batteries with high performance. CNCs display an intrinsically high aspect ratio and a large surface area and contain a large amount of hydroxyl groups offering a facile platform for chemical interactions. Density functional theory calculations suggest that the electron-rich functional groups on CNCs deliver robust binding energies with polysulfides. In this work, CNCs not only firmly confine sulfur and polysulfides in the cathode as a robust binder, but also further hinder polysulfide shuttling to the Li anode as a polysulfide stopper on a separator. Consequently, the as-prepared Li-S batteries demonstrate outstanding cycling performance even under the conditions of high sulfur content of 90 wt % (63 wt % in the cathode), high loading of 8.5 mg cm-2, and high temperature of 60 °C. These results sufficiently demonstrate that CNCs have significant application potential in Li-S battery technologies.

Enantioselective HPLC Analysis to Assist the Chemical Exploration of Chiral Imidazolines.

In the present work, we illustrate the ability of high-performance liquid chromatography (HPLC) analysis to assist the synthesis of chiral imidazolines within our medicinal chemistry programs. In particular, a Chiralpak® IB® column containing cellulose tris(3,5-dimethylphenylcarbamate) immobilized onto a 5 μm silica gel was used for the enantioselective HPLC analysis of chiral imidazolines synthesized in the frame of hit-to-lead explorations and designed for exploring the effect of diverse amide substitutions. Very profitably, reversed-phase (RP) conditions succeeded in resolving the enantiomers in nine out of the 10 investigated enantiomeric pairs, with α values always higher than 1.10 and RS values up to 2.31. All compounds were analysed with 50% (v) water while varying the content of the two organic modifiers acetonitrile and methanol. All the employed eluent systems were buffered with 40 mM ammonium acetate while the apparent pH was fixed at 7.5. Based on the experimental results, the prominent role of π-π stacking interactions between the substituted electron-rich phenyl groups outside of the polymeric selector and the complementary aromatic region in defining analyte retention and stereodiscrimination was identified. The importance of compound polarity in explaining the retention behaviour with the employed RP system was readily evident when a quantitative structure-property relationship study was performed on the retention factor values (k) of the 10 compounds, as computed with a 30% (v) methanol containing mobile phase. Indeed, good Pearson correlation coefficients of retention factors (r - log k1st = −0.93; r - log k2nd = −0.94) were obtained with a water solubility descriptor (Ali-logS). Interestingly, a n-hexane/chloroform/ethanol (88:10:2, v/v/v)-based non-standard mobile phase allowed the almost base-line enantioseparation (α = 1.06; RS = 1.26) of the unique compound undiscriminated under RP conditions.

Mussel-inspired polydopamine treated Si/C electrode as high-performance anode for lithium-ion batteries

In this paper, we report a mussel-inspired polydopamine coating on the Si/C electrode via a simple immersion process to improve the electrochemical performance such as cycle stability and rate capability. The nanometer-thick polydopamine coating layer enables fast Li+ transport at the interfaces and takes part in the formation of SEI due to the electron-rich amine group. The PD coated Si/C electrode exhibits good performance in long cycling test. Compare with the uncoated Si/C electrode, the capacity retention of the coated electrode is improved from 59.5% to 80% after 200 cycles. X-ray photoelectron spectroscopy, transmission electron microscopy and scanning electron microscopy prove that PD coating really promotes the formation of uniform and dense SEI and reduces cracks on the electrode surface. Meanwhile, the pulverization of electrodes which breaks the electrical contact with the current collector is alleviated.

Acetic Acid Assisted Crystallization Strategy for High Efficiency and Long-Term Stable Perovskite Solar Cell.

Improving the quality of perovskite poly‐crystalline film is essential for the performance of associated solar cells approaching their theoretical limit efficiency. Pinholes, unwanted defects, and nonperovskite phase can be easily generated during film formation, hampering device performance and stability. Here, a simple method is introduced to prepare perovskite film with excellent optoelectronic property by using acetic acid (Ac) as an antisolvent to control perovskite crystallization. Results from a variety of characterizations suggest that the small amount of Ac not only reduces the perovskite film roughness and residual PbI2 but also generates a passivation effect from the electron‐rich carbonyl group (C=O) in Ac. The best devices produce a PCE of 22.0% for Cs0.05FA0.80MA0.15Pb(I0.85Br0.15)3 and 23.0% for Cs0.05FA0.90MA0.05Pb(I0.95Br0.05)3 on 0.159 cm2 with negligible hysteresis. This further improves device stability producing a cell that maintained 96% of its initial efficiency after 2400 h storage in ambient environment (with controlled relative humidity (RH) <30%) without any encapsulation.

Magnetic poly(aniline-co-5-sulfo-2-anisidine) as multifunctional adsorbent for highly effective co-removal of aqueous Cr(VI) and 2,4-Dichlophenol

The common coexistence of heavy metal ions (HMIs) and toxic organic matters (OMs) arouses public concerns for their combined toxicity and carcinogenicity. The magnetic poly[aniline(AN)-co-5-sulfo-2-anisidine(SA)] (AN-SA/Fe3O4) was synthesized by an oxidative copolymerization method for the highly-effectively simultaneous removal of Cr(VI) and 2,4-dichlorophenol (2,4-DCP) from aqueous solution. The novel adsorbent exhibited ultra-strong adsorption capacities for sole Cr(VI) and sole 2,4-DCP. The mechanism studies revealed that Cr(VI) species (HCrO4− and Cr2O72− in solution pH as 5) were reduced to Cr(III) by the –NH–/–NH2 groups after attaching to the protonated binding sites of AN-SA/Fe3O4 through electrostatic attraction. By contrast, multiple reactions involving the n-π electron donor-acceptor (EDA) interaction, π-π stacking and hydrogen bond contributed to the elimination of 2,4-DCP. In binary system, the coexistent Cr(VI) and 2,4-DCP elevated mutual adsorption capacities by 88.1% and 102.1%, respectively. Specially, 2,4-DCP can form bridge interactions with both Cr(VI) and Cr(III) due to conjugate effect. This property enabled Cr(VI) to additionally link to the hydrophobic sites, except for the hydrophilic sites, via 2,4-DCP bridges. Moreover, the produced Cr(III) can forcefully captured 2,4-DCP with the electron-rich groups (i.e., NH, N, SO3H, OCH3) on AN-SA/Fe3O4 to form the multi-components complexes. The bridge interactions (i.e., n-π EDA interaction, complexation) created the newly available sites for Cr(VI) and 2,4-DCP, resulting in enlarged adsorbance and synchronous removal on AN-SA/Fe3O4 in coexisting system. In addition, the high proportion of N groups generated by Cr(VI) oxidation also devoted to the uptake enhancement due to its strong affinity for 2,4-DCP. Overall, the high-performance and synergistic removal qualified AN-SA/Fe3O4 as a multifunctional adsorbent for the integrated treatment of HIMs-OMs hybrid pollutants.

Strongly emitting and long-lived silver indium sulfide quantum dots for bioimaging: Insight into co-ligand effect on enhanced photoluminescence

Nanoscale ternary chalcogenides have attracted increasing research interest due to their merits of tunable properties and diverse applications in energy and biomedical fields. In this article, silver indium sulfide quantum dots supported by glutathione and polyethyleneimine as dual-ligands have been synthesized through an environmentally friendly and reproducible aqueous method. An emission quantum yield up to 37.2% has been achieved by glutathione as co-ligand bearing electron-rich groups, much higher than that of polyethyleneimine coated quantum dots (4.97%). Both spectroscopic and structural characterizations demonstrate that the photoluminescence enhancement is attributed to change of surface properties by glutathione as co-ligand. Dynamic light scattering (DLS) results and thermogravimetric analysis (TGA) reveal that glutathione covers the QDs with a higher density on the nanocrystal surface than other co-ligands. Therefore, it can effectively passivate the surface trap centers, thus decreasing the non-radiative emission. Moreover, the resultant silver indium sulfide quantum dots present surprisingly long lifetime of 3.69 μs, excellent fluorescent stability and low cytotoxicity, which enables them to be ideal candidate for real-time bioimaging.

Miquel Costas.

"The secret of being a successful scientist is, I guess, a combination of intelligence, hard work, perseverance, and serendipity. I admire intelligent originality …" Find out more about Miquel Costas in his Author Profile.

Asymmetric trifluoromethylthiolation of azlactones under chiral phase transfer catalysis.

The first enantioselective method for the installation of the SCF3 group at the C-4 position of azlactones is described in the present communication under quinidinium phase transfer catalysis. The higher performance of substrates containing electron-rich 2-aryl groups at the azlactone was rationalized using DFT calculations.

Ionic conductivity enhancement in solid polymer electrolytes by electrochemical in situ formation of an interpenetrating network.

Various overoxidized poly(1H-pyrrole) (PPy), poly(N-methylpyrrole) (PMePy) or poly(3,4-ethylenedioxythiophene) (PEDOT) membranes incorporated into an acrylate-based solid polymer electrolyte matrix (SPE) were directly electrosynthesized by a two-step in situ procedure. The aim was to extend and improve fundamental properties of pure SPE materials. The polymer matrix is based on the cross-linking of glycerol propoxylate (1PO/OH) triacrylate (GPTA) with poly(ethylene glycol) diacrylate (PEGDA) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) as a conducting salt. A self-standing and flexible polymer electrolyte film is formed during the UV-induced photopolymerization of the acrylate precursors, followed by an electrochemical polymerization of the conducting polymers to form a 3D-IPN. The electrical conductivity of the conducting polymer is destroyed by electrochemical overoxidation in order to convert the conducting polymer into an ion-exchange membrane by introduction of electron-rich groups onto polymer units. The resulting polymer films were characterized by scanning electron microscopy, cyclic voltammetry, electrochemical impedance spectroscopy, differential scanning calorimetry, thermal analysis and infrared spectroscopy. The results of this study show that the combination of a polyacrylate-matrix with ion selective properties of overoxidized CPs leads to new 3D materials with higher ionic conductivity than SPEs and separator or selective ion-exchange membrane properties with good stability by facile fabrication.

Diindolotriazatruxene-Based Hole-Transporting Materials for High-Efficiency Planar Perovskite Solar Cells.

A novel set of hole-transporting materials (HTMs) based on π-extended diindolotriazatruxene (DIT) core structure with electron-rich methoxy-engineered functional groups were designed and synthesized via a facile two-step procedure. All compounds were afforded from inexpensive precursors without a complex purification process. Cyclic voltammograms indicate that the resulting HTMs exhibit suitable highest occupied molecular orbital (HOMO) energy levels, which facilitate efficient hole injection from the valence band of perovskites into the HOMO of DIT-based HTMs as confirmed by time-resolved photoluminescence. Notable power conversion efficiency of the planar perovskite solar cells with low-temperature device fabrication achieved 18.21% utilizing D2, which is competitive with the corresponding devices based on the common Spiro-OMeTAD-based HTMs. The results manifest that DIT-based compounds are promising HTMs for constructing high-efficiency planar perovskite solar cells with low-cost solution processing procedures.

Computational study on optoelectronic and charge transport properties of diketopyrrolopyrrole-based A-D-A-D-A structure molecules for organic solar cells.

Eight novel diketopyrrolopyrrole (DPP)-based A-D-A-D-A structure molecules were designed for organic solar cells (OSCs) applications. In these molecules, the electron-deficient DPP and dicyanovinyl groups were used as the acceptor groups and different planar electron-rich groups were employed as the donor π-bridges. Applying the B3LYP/6-31G (d,p) and TD-B3LYP/6-31G (d,p) methods, the optoelectronic and charge transport properties were investigated. It turned out that the different π-bridges can tune effectively the frontier molecular orbital energy levels, band gap, and absorption spectra. Furthermore, the different π-bridges also affect the charge transport properties of the designed molecules. Our results suggest that the investigated molecules can serve as donor materials. Additionally, some investigated molecules can also be used as hole and/or electron transport materials for OSCs. Graphical abstract A series of novel A-D-A-D-A molecules are investigated systematically. The optical and electronic properties can be tuned effectively by the π-bridges. All derivatives can be used as donor materials for OSCs. Some designed molecules can be used as hole and/or electron transport materials. The different π-bridges do not significantly affect the stability of the molecules.