Electron-deficient Groups Research Articles

Facile synthesis of functionalized quinolinones in a green reaction medium and their photophysical properties.

A facile and green chemical approach was successfully developed to construct functionalized quinolinones utilizing substituted alcohols, alkyl acetoacetate, and α-bromo ketones. Various quinolinones bearing either electron-rich or electron-deficient groups at different positions were synthesized in moderate to good yields under mild reaction conditions. The plausible mechanistic pathway for this transformation is supported by experimental evidence and control experiments. This simple approach for synthesizing quinolinones could open new avenues for discovering novel biological and pharmaceutical compounds. The use of affordable nickel catalysts, mild reaction conditions, operational simplicity, and high atom economy are attractive features of this method. Furthermore, the synthetic efficiency has been demonstrated through gram-scale experiments. Our research also provides valuable insights into the photophysical properties of the synthesized derivatives. Notably, compound 6n exhibited the highest Stokes shift (216 nm) in DCM solvent. Furthermore, compounds 5d and 6j showed positive solvatochromism, displaying a stronger emission as the solvent polarity increased. Additionally, compound 6j displayed aggregation-induced emission (AIE) properties in a DMSO : water mixture, making it suitable for use as a security ink, highlighting its potential applications in various fields.

Adsorbents for hydrogen-bond accepting hazardous chemicals by post-synthetic modification of UiO-66-NH2.

Adsorbents for hydrogen-bond accepting chemicals such as organophosphates are developed by post-synthetically modifying UiO-66-NH2 through two analogous condensation reactions to incorporate hydrogen-bond donating adsorbent groups. When benzaldehydes are employed as coupling partners, the resulting imine-functionalized MOFs show improvements in uptake capacity with increasingly electron-deficient adsorbent groups. By contrast, when the coupling partners are benzoic acids, the resulting amide-functionalized MOFs exhibit improvements in uptake capacity with increasingly electron-rich adsorbent groups. Both modification approaches also increase binding affinity for organophosphates relative to unmodified UiO-66-NH2, demonstrating successful modification of the MOF scaffold to create adsorbents for hazardous chemicals.

Novel indacene-1,3,5,7-tetraone-based polymerized small molecular acceptors for efficient all-polymer solar cells

Polymerized small molecular acceptors (PSMAs) as polymer acceptors are demonstrated to show great potential in fabricating high-performance all-polymer solar cells (all-PSCs), but the available type of electron-deficient end-capping groups for...

Intramolecular through-space charge transfer between benzofuran and ynone groups on a naphthalene spacer.

We have developed a new scaffold that exhibits an efficient intramolecular through-space charge transfer (CT). In this design, electron-rich benzofuran and electron-deficient ynone groups are placed strategically in proximity via a naphthalene spacer. Charge transfer is supported by distinct CT bands in the visible region (>500 nm) in their UV-vis absorption and emission spectra.

Unleashing the dye adsorption potential of polyaminoimide homopolymer: DFT, statistical physics, site energy and pore size distribution analyses

The efficient removal of Congo Red (CR) dye from aqueous solutions is an important issue in environmental protection. This study presents the synthesis and optimization of a polyaminoimide homopolymer (PHP) adsorbent for the removal of CR dye. To optimize the synthesis of PHP, ten different compositions of maleic anhydride and ethylene diamine were tested, with PHP3 demonstrating the highest efficacy. The adsorption process was further enhanced by optimizing pH, temperature, adsorbent dose, and initial dye concentration. Isotherm and kinetic studies revealed that the Langmuir-Freundlich model and the pseudo-second-order kinetics best described the adsorption process. Moreover, PHP3 demonstrated significantly greater selectivity for CR compared to Synozol yellow, and Sulfasalazine. Advanced statistical models were used to analyze the adsorption data, and the single-layer model with single energy (M1) being the most suitable, suggesting that CR molecules were adsorbed onto PHP3 in a perpendicular position through a multimolecular process, the adsorption process is physical, endothermic, spontaneous and specific surface area of PHP3 increased from 54.31 to 115.74 m2 g−1 as temperature rose from 288 to 318 K. Site energy distribution and pore size distribution studies showed that PHP3 has a heterogeneous energy distribution on its surface, and that the adsorption of CR dye primarily takes place in the macropores of PHP3. Density Functional Theory analysis indicated that PHP3 has electron-rich amine groups that can interact with electron-deficient sulfonate groups in CR, while electron-poor amide groups in the polymer can interact with the electron-rich azo group in Congo Red. It also shows that the presence of NaF, Na2SO4, and KCl salts did not significantly affect the CR adsorption, indicating the potential affinity/selectivity of PHP3 towards CR dye. The findings suggest that PHP3 could be an effective and promising adsorbent for industrial applications in wastewater treatment.

Incorporating Naphthalene and Halogen into Near-Infrared Double-Cable Conjugated Polymers for Single-Component Organic Solar Cells with Low-Voltage Losses.

The invention of near-infrared pedant-based double-cable conjugated polymers has demonstrated remarkable efficacy in single-component organic solar cells (SCOSCs). This work focuses on the innovative double-cable conjugated polymers aimed at attaining good absorption and suitable energy levels. Specifically, in the aromatic side units, the electron-donating (D) part is designed using a thieno[3,4-c]pyrrole-4,6-dione (TPD) as a core unit, flanked by two cyclopentadithiophene groups on either side. The electron-deficient (A) terminal groups consist of 2-(3-oxo-2,3-dihydro-1H-cyclopenta[b]naphthalen-1-ylidene) malononitrile (NC), which can be further modified through fluorination to modulate the physical properties and packing modes of the acceptor material. The resulting double-cable conjugated polymers exhibit broad absorption spectra spanning 500-850 nm and possess lowered Frontier energy levels when incorporating fluorine elements, providing decreased voltage losses in SCOSCs. Therefore, SCOSCs fabricated using these polymers have demonstrated power conversion efficiencies ranging from 7.6 to 10.2%, in which fluorine-containing double-cable conjugated polymers showed higher PCEs due to more favorable crystalline packing, enhanced exciton dissociation probability, and charge-transporting ability.

Ammonium perchlorate catalyzed with novel porous Mn-doped Co3O4 microspheres: superior catalytic activity, advanced decomposition kinetics and mechanisms

Mn-doped Co3O4 nanoparticles of 15 nm were developed via solvothermal synthesis. Mn@Co3O4 microspheres were developed via controlled annealing treatment at 600 °C. Mn@Co3O4 microspheres demonstrated an average diameter of 5.5 µm, with specific area (BET) of 73.7 m2 g−1. The pore diameter was centered at 13.1 nm, and the mean pore size was 16 nm; porous structure could secure extensive interfacial surface area. Mn@Co3O4 microspheres were integrated into ammonium perchlorate (AP) matrix. The catalytic activity of Mn@Co3O4 on AP decomposition was assessed via DSC and TGA/DTG. Whereas Mn@Co3O4/AP nanocomposite demonstrated decomposition enthalpy of 1560 J g−1, pure AP demonstrated 836 J g−1. While Mn@Co3O4/AP nanocomposite demonstrated one decomposition temperature at 310 °C,pure AP exposed two decomposition stages at 298 °C, and 453 °C. Decomposition kinetics was investigated via isoconversional (model free) and model fitting. Kissinger, Kissinger–Akahira–Sunose (KAS), integral isoconversional method of Ozawa, Flyn and Wall (FWO), and differential isoconversional method of Friedman. Mn@Co3O4/AP demonstrated apparent activation energy of 149.7 ± 2.54 kJ mol−1 compared with 173.16 ± 1.95 kJ mol−1 for pure AP. While AP demonstrated sophisticated decomposition models starting with F3 followed by A2, Mn@Co3O4/AP nanocomposite demonstrated A3 decomposition model. Mn@Co3O4 can expose active surface sites; surface oxygen could act as electron donor to electron deficient perchlorate group. Furthermore, Mn@Co3O4/AP could act as adsorbent of released NH3 gas with efficient combustion. This study shaded the light on Mn@Co3O4 as potential catalyst for AP decomposition.

Low-Dimensional and High-Crystallinity Carbonyl Cathodes Prepared by Physical Vapor Deposition for Green Aluminum Organic Batteries.

We report a low-cost, high theoretical specific capacity π-conjugated organic compound (PTCDA) with C═O active centers as the cathode material in aluminum organic batteries. In addition, in order to improve the electron transport rate of PTCDA, a new method is proposed in this paper, which uses physical vapor deposition (PVD) method to make PTCDA recrystallize and grow on stainless steel and quartz glass substrates to improve its crystallinity. The increase of crystallinity expands the PTCDA π-π-conjugated system, making electrons more delocalized, which is beneficial to the transmission rate of electrons and ions, thereby enhancing the conductivity of the material. The experimental results show that compared with pristine PTCDA, PTCDA(Ss) and PTCDA(G) with higher crystallinity have better cycling stability and rate capability. The DFT (density functional theory) results indicated that the electron-deficient carbonyl group in the PTCDA molecule could reversibly coordinate/dissociate with the positively charged Al complex ions (AlCl2+). This research work provides insights into the rational design of low-dimensional, high-crystallinity, high-performance cathode materials for green aluminum organic batteries.

Disproportionation and dimerisation of kynurenic acid under UV light

In this work, we report on the photo-induced oxidation of kynurenic acid (KNA) by the triplet-excited KNA in a neutral aqueous solution. This reaction is confirmed by two different time-resolved methods: optical spectroscopy and chemically induced dynamic nuclear polarization (CIDNP). The disproportionation reaction proceeds with the rate constant of (6.0 ± 1.2) × 107 M−1s−1 via the mechanism of H-atom transfer to the photoexcited KNA in the triplet state, yielding the reduced and oxidized forms of KNA, KNAH2− and KNA(-H)−, respectively. The formation of these radicals is confirmed by a good proportionality relationship between the calculated proton hyperfine coupling constants of both radicals and the signal intensities in 1H CIDNP spectra detected after the recombination of the geminate radical pairs formed immediately after the laser pulse. The oxidized forms of KNA recombine yielding dimeric KNA-KNA products crosslinked via different positions within aromatic systems. The oxidized form of KNA, KNA(-H)−, could be of high biological interest due to its ability to recombine with other electron-deficient radicals, including tryptophan and tyrosine radicals, unravelling a radical pathway for the covalent attachment of KNA to proteins in living tissues.

Study on preparation of pillararene cocrystals by liquid-assisted grinding

Liquid-assisted grinding (LAG) has received wide attention in chemical synthesis field. Here, we reported that LAG provides a smart strategy to build macrocyclic cocrystal (MCC), achieving quick modification. The macrocyclic cocrystal has been assembled by electronegative permethylated pillar[5]arenes (EtP5) and electropositive ligands. We select three ligands with strong electron-deficient groups for cocrystal preparation with EtP5 by LAG and judge whether the grinding products are cocrystals by color change, Infrared (IR), Ultraviolet-visible (UV-vis) absorption, and X-ray diffraction (XRD). We demonstrated that the same structure as solvent cocrystal can be obtained by LAG. We obtained the single crystal structure of the EtP5 cocrystal with the promising ligand, confirming the formation of cocrystals and the reliability of the liquid-assisted grinding method.

Direct 2-Pyridyl-Alkylation of Benzyne with N-Alkylpyridinium Salts

AbstractA 2-pyridyl-alkylation of benzyne using N-alkylpyridinium salts has been developed under either photochemical or thermal conditions. This metal-free dicarbofunctionalization of benzyne undergoes a de Mayo-type process including cascade dearomative [3+2] cycloaddition and rearomative ring-opening reaction. An electron-deficient N-cyclic alkyl group was necessary. A formal ortho-C–H arylation of pyridine has been achieved.

Recent Advances in Highly Fluorescent Hydrazine-Inserted Pyrrole-Based Diboron-Anchoring Fluorophores: Synthesis and Properties

AbstractHydrazine-inserted pyrrole-based diboron fluorophores that display strong fluorescence in either the solution or solid state are widely used in biomedicine and optoelectronic materials science. A growing demand calls for multiple strategies for generating novel fluorophores to solve problems of small Stokes shifts and poor solid-state fluorescence. By changing their frameworks, several series of novel diboron compounds have recently been developed as increasingly valuable classes of fluorophores owing to their tunable structures and outstanding spectroscopic properties, such as high fluorescence quantum yields, large Stokes shifts, high photostability, and low LUMO energy levels due to the presence of electron-deficient BF2 groups. This review mainly highlights key synthetic strategies for the fluorophores BOPHY, BOPPY, and BOAPY developed by our group, together with the superior properties of these compounds. Significant photophysical data for these fluorophores in solution and solid states are included within the scope of this review. The facile functionalization of these fluorophores permits practical structural modifications to generate novel versatile dyes with excellent chemical and photophysical properties. We believe that these fluorophores hold promise to make important contributions in a wide range of applications.1 Introduction2 BOPHY Fluorophore2.1 Discovery of BOPHY and its Fundamental Properties2.2 Synthesis and Properties of Modified BOPHY Derivatives3 BOPPY and BOPYPY Fluorophores3.1 Discovery of BOPPY and BOPYPY, and Their Fundamental Properties3.2 Synthesis and Properties of Benzo-Fused BOPPYs from Isoindoles3.3 Nucleophilic Substitution and Cross-Coupling Reactions of Halogenated BOPPYs3.4 Knoevenagel Reaction4 BOAPY and BOPAHY Fluorophores5 Conclusion

Synthesis and characterization of phenothiazine sensor for spectrophotometric and fluorescence detection of cyanide.

A sensitive and selective phenothiazine-based sensor (PTZ) has been successfully synthesized. The sensor PTZ displayed specific identification of CN- 'turn-off' fluorescence responses with a quick reaction and strong reversibility in an acetonitrile:water (90:10, V/V) solution. The sensor PTZ for detecting CN- exhibits the marked advantages of quenching the fluorescence intensity, fast response time (60 s), and low value of the detection limit. The concentration that is authorized for drinking water by the WHO (1.9μM) is far higher than the detection limit, which was found to be 9.11 × 10-9 . The sensor displays distinct colorimetric and spectrofluorometric detection for CN- anion due to the addition of CN- anion to the electron-deficient vinyl group of PTZ, which reduces intramolecular charge transfer efficiencies. The 1:2 binding mechanism of PTZ with CN- was validated by fluorescence titration, Job's plot, HRMS, 1 H NMR, FTIR analysis, and density functional theory (DFT) investigations, among other methods. Additionally, the PTZ sensor was successfully used to precisely and accurately detect cyanide anions in actual water samples.

Nickel-catalyzed Suzuki cross-coupling reaction of alkyl triaryl phosphonium salts

The Suzuki cross-coupling reaction of triphenyl quaternary phosphonium triflates with boronic acids was reported. The reaction was catalyzed by Ni(COD)2 without additional ligand, using Cs2CO3 as the base in toluene, and various biphenyls were synthesized in medium to excellent yields. This protocol has a wide adaptability to boronic acids, and many functional groups are tolerated. The method is scalable and could be performed on the gram scale. The regioselective arylation of differently substituted phenyl phosphonium triflates was observed at the side of electron-deficient phenyl group.

Mechanistic insight into the ligand-controlled regioselective hydrocarboxylation of aryl olefins with palladium catalyst: A computational study

The density functional theory (DFT) calculations were employed to investigate the reaction mechanisms of Pd-catalyzed hydrocarboxylation of styrene with different ligands. The regioselectivity is controlled by the employed ligand. By using the ligand of tris[4-(trifluoromethyl)phenyl]phosphine, the electron-deficient p-CF3 group would cause the branched 2-arylpropionic acid to be the major product. The observed regioselectivity could be attributed to the electronic effects. In the presence of tris(2-methoxyphenyl)phosphine ligand, the bulky o-OMe group would reverse the reaction to produce linear 3-arylpropionic acid. Moreover, the existed CH···Π interaction could also account for the regioselectivity.

NBS-mediated bromination and dehydrogenation of tetrahydro-quinoline in one pot: scope and mechanistic study.

A facile and general approach was developed for the efficient construction of functionalized bromoquinolines by the dehydrogenation of tetrahydroquinolines using NBS as the electrophile and as oxidant. The cascade transformation proceeded with good functional group tolerance under metal-free conditions with a short reaction duration. Various tetrahydroquinolines bearing either electron-rich or electron-deficient groups at different positions were successfully converted into the corresponding target products in moderate to high yields under mild conditions. It is worth noting that the obtained polybromoquinolines could further undergo classic metal-catalyzed cross-coupling reactions with good regioselectivity. The Sonagashira coupling reaction occurred regioselectively in the C-6 position of the obtained products followed by a Suzuki coupling reaction to give multifunctionalized quinolines. The mechanism indicated that electrophilic bromination/radical dehydrogenation sequences occurred in one pot.

A combination of surface-initiated atom transfer radical polymerization and photo-initiated “thiol-ene” click chemistry: Fabrication of functionalized macroporous adsorption resins for enrichment of glycopeptides

A hydrophilic adsorbent (Cys@poly(AMA)@MAR) was successfully prepared for the enrichment of N-glycopeptides via surface-initiated atom transfer radical polymerization (SI-ATRP) and photo-initiated “thiol-ene” reaction using monodisperse macroporous adsorbent resin (MAR) as adsorption matrix. Due to the presence of electron-deficient acrylic groups and electron-rich vinyl groups in allyl methacrylate (AMA), both of them can participate in free radical reaction. Therefore, the polymerization time of SI-ATRP was optimized. The resulting poly(AMA)@MAR was modified with l-cysteine (L-Cys) via photo-initiated “thiol-ene” reaction, and the amount of vinyl retained was determined by measuring the adsorption of Cu2+. The Cys@poly(AMA)@MAR pendant brushes with high density of amine and carboxyl groups could capture N-glycopeptides from IgG digest and human serum digest by hydrophilic interaction. The 22 N-glycopeptides were identified from IgG digest and the limit of detection reached 10 fmol. The 319 N-glycosylation sites and 583 N-glycopeptides were identified from 2 μL human serum digest and mapped to 147 glycoproteins. It demonstrates great potential and commercialization prospects for the enrichment of N-glycopeptides.

Electron-deficient moiety regulated structure: an efficient strategy for the design of a highly sensitive cyanide “turn-on” fluorescent probe

Developing fluorescent probes for the cyanide diagnosis is necessary as its extensive existence will seriously harm human health. Herein, the strategy for designing three novel probes came from our previously reported “turn-on” fluorescent probe, which was switched from a “turn-off” probe by inserting an electron-deficient benzothiadiazole (BTD) into a triphenylamine (TPA)-based dicyanovinyl (MT) compound with a phenyl group (Ph) as π-bridge (TPA-BTD-Ph-MT). To further investigate the effects of the electron-deficient group, BTD was firstly replaced by a stronger electron-deficient group of 2,3-diphenylquinoxaline (DPQ) to obtain TPA-DPQ-Ph-MT (P1). Based on P1 molecule, N-phenylcarbazole (PCZ), and thiophene (Th) were respectively used as a substitute to obtain PCZ-DPQ-Ph-MT (P2) and TPA-DPQ-Th-MT (P3) probes for investigating the effect of the electron donor and π-bridge on the fluorescent probe. P1 exhibited significant “turn-on” fluorescence response toward cyanide anion (CN−) with the best sensitivity and anti-interference performance. The sensing mechanism of P1 toward CN− was demonstrated and a good linearity was obtained in the wide concentration range of 0.025–40.0 μM with a low detection limit of 0.058 μM. Furthermore, P1 was successfully employed to determine CN– in food samples and image CN– in living cells and BALB/c mice, revealing its great practical potential for discriminative detection CN– in the fields of food and biological studies. Therefore, the strategy based on structure regulation provided good prospects for optimizing fluorescent probes.

Highly efficient blue light-emitting polymer containing a Benzo[b]naphtho[1,2-d]thiophene -S,S-dioxide unit

The dibenzothiophene-S,S-dioxide (SO) possess strong but unmatched electron-withdrawing ability when connected to a normally used donor. Here, to lower its electron-withdrawing ability, we synthesized a benzo[b]naphtho[1,2-d]thiophene-S,S-dioxide (NSO) electron-deficient acceptor by using a naphthalene ring to replace one of the benzene rings in the SO unit. The copolymers PPF-NSs and PPF-NSOs were synthesized by introducing the NSO and benzo[b]naphtho[1,2-d] thiophene (NS) unit into polyfluorene backbone. A systematic study was presented based on the copolymers from the aspect of theoretical calculation, photophysical properties, electrochemical properties, and electroluminescent properties. For the PPF-NSs film, intermolecular energy transfer should be the main mechanism of photoluminescence. Whereas, intramolecular charge transfer played the main role in the photoluminescence mechanism for PPF-NSOs film due to the existence of the strong electron-deficient group (NSO). The PPF-NSOs acquired superior blue emission with maximum luminous efficiency (LEmax) of 8.16 cd A−1 and a CIE of (0.16, 0.25) at a low acceptor concentration of 3%, while the copolymer (PPF-NS1) based on energy transfer also achieved a satisfactory performance with LEmax of 5.20 cd A−1 and a CIE of (0.17, 0.18).

Copper-catalyzed α-selective cross-dehydrogenative coupling of BODIPY dyes with aldehydes: A new route to acylated BODIPYs and dipyrromethenes

A novel copper-catalyzed direct acylation of BODIPYs with aldehydes via C–H bond activation was developed, in which acyl radicals were formed from aldehydes in the presence of TBHP as radical initiator, and selectively reacted with BODIPYs at the α-positions. This radical oxidative dehydrogenative cross-coupling reaction showed excellent functional group tolerance, and both heteroaromatic and aliphatic aldehydes could be effectively reacted to BODIPYs. Comparing with those of the corresponding starting BODIPYs, those α-acylated BODIPYs showed red-shifted absorption and emission, as well as decreased both HOMO and LUMO energies due to the installation of electron-deficient carbonyl groups. Furthermore, the α-acylated BODIPY provided an efficient access to α-acylated dipyrrin by removal of the BF2 protecting groups, which showed sensitive and selective “turn-on” fluorescence response toward Zn2+ ion in aqueous buffer solution and living cells.