Electron-donating Functional Groups Research Articles

Ni/C-catalyzed aminocarbonylation of aryl halides using DMF as an amine source and o-chlorophenyl formate as a CO surrogate and promoter

We developed Ni/C-catalyzed aminocarbonylation of aryl halide by utilizing DMF and o-chlorophenyl formate to produce tertiary amides. This reaction employed o-chlorophenyl formate (OCPF) as a CO source, and it also acts as a promoter for the selective tertiary amide synthesis. Even under ideal conditions, this newly established approach considerably reduces the generation of homo-coupled biaryl ketone and phenoxy carbonylation byproducts. This protocol shows remarkable activity towards a wide range of aryl halides containing electron-donating and electron-withdrawing functional groups. This methodology represents the moisture-sensitive ligand-free, co-catalyst-free, and heterogeneous recyclable catalyst. The Ni/C catalyst was utilized for up to five consecutive runs. The fresh and recycled Ni/C catalysts were characterized using several techniques, including TEM, SEM, EDX, XRD, and TGA analysis.

Synergistic Effects of Amine Functional Groups and Enriched-Atomic-Iron Sites in Carbon Dots for Industrial-Current-Density CO2 Electroreduction.

Metal phthalocyanine molecules with Me-N4 centers have shown promise in electrocatalytic CO2 reduction (eCO2R) for CO generation. However, iron phthalocyanine (FePc) is an exception, exhibiting negligible eCO2R activity due to a higher CO2 to *COOH conversion barrier and stronger *CO binding energy. Here, amine functional groups onto atomic-Fe-rich carbon dots (Af-Fe-CDs) are introduced via a one-step solvothermal molecule fusion approach. Af-Fe-CDs feature well-defined Fe-N4 active sites and an impressive Fe loading (up to 8.5wt%). The synergistic effect between Fe-N4 active centers and electron-donating amine functional groups in Af-Fe-CDs yielded outstanding CO2-to-CO conversion performance. At industrial-relevant current densities exceeding 400mA cm-2 in a flow cell, Af-Fe-CDs achieved >92% selectivity, surpassing state-of-the-art CO2-to-CO electrocatalysts. The in situ electrochemical FTIR characterization combined with theoretical calculations elucidated that Fe-N4 integration with amine functional groups in Af-Fe-CDs significantly reduced energy barriers for *COOH intermediate formation and *CO desorption, enhancing eCO2R efficiency. The proposed synergistic effect offers a promising avenue for high-efficiency catalysts with elevated atomic-metal loadings.

Difluoro Dipyridomethene Boron Complexes: Synthesis, Characterization, and Ab Initio Calculations.

Molecular engineering studies on the meso-cyano difluoro dipyridomethene boron complexes are presented and two series (a and b) of novel fluorophores are extensively studied. Halogenated derivatives were reacted under Suzuki-Miyaura or Sonogashira cross coupling reactions to introduce electron-donating or electron-withdrawing functional groups on positions 1 and 2 of the aromatic ligand. All derivatives were obtained in 14-90% yields and studied in detail by structural, photophysical, and computational analyses. Both series display excellent emissive properties in solution with blue to orange fluorescence emission upon blue light absorption and promising features as solid emitters. All the spectroscopic measurements are supported and confirmed by first-principles theoretical calculations combining TD-DFT and CC2. Series b, featuring an aryl substituent onto position 1 of the aromatic core, showed significantly large Stokes shifts values.

Precise local functionalization of covalent organic framework for efficient carrier separation in photocatalytic H2 evolution

Improving carrier transport rate and suppressing carrier recombination are two huge challenges in the photocatalytic applications of covalent organic frameworks (COFs)-based semiconductors. In this study, we propose a strategy to enhance carrier transport efficiency by regulating the local microenvironment of the electronic characteristics in the acceptors through structural modification. Three different functional group-modified fluorenone-based COFs were successfully synthesized through precise design. The results demonstrate that the photocatalytic hydrogen evolution activities of COFs modified with electron-donating functional groups are significantly higher than that of COFs modified by electron-withdrawing functional groups. Specifically, the photocatalytic hydrogen evolution performance of phenyl-modified FOOPh-COF could reach 228.5 mmol h−1g−1, which is 11.8 times higher than that of Br atom-modified FOOBr-COF (19.3 mmol h−1g−1). Femtosecond time-resolved transient absorption spectroscopy (fs-TAS) results reveal that introducing phenyl groups into the acceptor significantly enhances its inhibitory effect on the carrier recombination. Density functional theory calculations further prove that modifying the acceptor by electron-donating functional groups can achieve the increased electron density in the CO active center. The electrons in the CO region in the phenyl-modified fluorenone structure are more enriched and delocalized, which can enhance the speed of electron migration, shorten the migration distance, and inhibit carrier recombination. After loading Pt, it has the lowest H* adsorption-free energy among three samples. This work clarifies the importance of the functionalization modification of COFs’ acceptors in regulating the local electronic environment and further provides new insights into the structure–activity relationship of fluorenone-based COF-based photocatalysts.

Removal characteristics of 53 micropollutants during ozonation, chlorination, and UV/H2O2 processes used in drinking water treatment plant

The removal of 53 emerging micropollutants (MPs), including 10 per- and polyfluorinated substances (PFASs), 25 pharmaceuticals and personal care products (PPCPs), 7 pesticides, 5 endocrine disrupters (EDCs), 3 nitrosamines, and 3 taste and odor compounds (T&Os), by chlorination, ozonation, and UV/H2O2 treatment was examined in deionized water and surface waters used as the raw waters in drinking water treatment plants (DWTPs) in South Korea. The UV/H2O2 treatment was effective in the removal of most MPs, whereas chlorination was selectively effective for 19 MPs, including EDCs (>70 %). MPs containing aromatic ring with electron-donating functional group, or primary and secondary amines were effectively removed by chlorination immediately upon reaction initiation. The removal of MPs by ozonation was generally lower than that of the other two processes at a low ozone dose (1 mg L−1), but higher than chlorination at a high ozone dose (3 mg L−1), particularly for 16 MPs, including T&Os. Compared in deionized water, the removals of MPs in the raw water samples were lower in all three processes. The regression models predicting the rate constants (kobs) of 53 MPs showed good agreement between modeled and measured value for UV/H2O2 treatment (R2 = 0.948) and chlorination (R2 = 0.973), despite using only dissolved organic carbon (DOC) and oxidant concentration as variables, whereas the ozonation model showed a variation (R2 = 0.943). Our results can provide the resources for determining which oxidative process is suitable for treating specific MPs present in the raw waters of DWTPs.

The structure-activity relationship for the electron-donating functional groups in hydrazone-linked COFs and their photocatalytic H2O2 production

Electron-donating group modification on covalent organic frameworks (COFs) would reasonably stimulate photocatalytic activity. However, the structure-activity relationship between the electron-donating capacity and the photocatalytic activity of electron-donating functional COFs remains greatly obscure. Herein, a series of functionalized hydrazone-linked COFs containing different electron-donating capacity groups (R-COF, R = H, Me, MeO, OH) were constructed. The results suggest that the existence of substituents with strong electron-donating capacity in R-COFs can enhance the conjugation effect and thereby accelerate the separation and transfer of photogenerated electron-hole pairs. And the stronger electron-donating capacity of groups are more favorable for the electron push-pull effect, which is beneficial for photocatalytic H2O2 production. Among them, MeO-COF had the highest H2O2 generation performance without sacrificial agents under air (847.9 μmol g−1 h−1), which is 4.95 times higher than that of H-COF. This work provides insights for the design of functionalized COFs to achieve efficient photocatalytic H2O2 production.

Electron-donating functional groups strengthen ligand-induced chiral imprinting on CsPbBr3 quantum dots

Chiral perovskite nanoparticles and films are promising for integration in emerging spintronic and optoelectronic technologies, yet few design rules exist to guide the development of chiral material properties. The chemical space of potential building blocks for these nanostructures is vast, and the mechanisms through which organic ligands can impart chirality to the inorganic perovskite lattice are not well understood. In this work, we investigate how the properties of chiral ammonium ligands, the most common organic ligand type used with perovskites, affect the circular dichroism of strongly quantum confined CsPbBr3 nanocrystals. We show that aromatic ammonium ligands with stronger electron-donating groups lead to higher-intensity circular dichroism associated with the lowest-energy excitonic transition of the perovskite nanocrystal. We argue that this behavior is best explained by a modulation of the exciton wavefunction overlap between the nanocrystal and the organic ligand, as the functional groups on the ligand can shift electron density toward the organic species-perovskite lattice interface to increase the imprinting.

Application of Inverse Design Approaches to the Discovery of Nonlinear Optical Switches.

Molecular switches, in which a stimulus induces a large and reversible change in molecular properties, are of significant interest in the domain of photonics. Due to their commutable redox states with distinct nonlinear optical (NLO) properties, hexaphyrins have emerged as a novel platform for multistate switches in nanoelectronics. In this study, we employ an inverse design algorithm to find functionalized 26R→28R redox switches with maximal βHRS contrast. We focus on the role of core modifications, since a synergistic effect with meso-substitutions was recently found for the 30R-based switch. In contrast to these findings, the inverse design optima and subsequent database analysis of 26R-based switches confirm that core modifications are generally not favored when high NLO contrasts are targeted. Moreover, while push-pull combinations enhance the NLO contrast for both redox switches, they prefer a different arrangement in terms of electron-donating and electron-withdrawing functional groups. Finally, we aim at designing a three-state 26R→28R→ 30R switch with a similar NLO response for both ON states. Even though our best-performing three-state switch follows the design rules of the 30R-based component, our chemical compound space plots show that well-performing three-state switches can be found in regions shared by high-responsive 26R and 30R structures.

Selective oxidation of organic pollutants over a new Co-based MOF via peroxymonosulfate activation under UV light: Performance and mechanism

The oxidation processes dominated by nonradical singlet oxygen (1O2) could accomplish highly selective oxidation, which attracted increasing attentions in recent years. However, the 1O2 generation path still remains ambiguous. In this study, a new 3D Co-based metal–organic framework (MOF) namely BUC-100 was solvothermally synthesized from CoCl2·6H2O, 1,3,5-tris(1-imidazolyl) benzene (TIB) and terephthalic acid (H2BDC). The as-prepared BUC-100 was used to selectively degrade various organic contaminants including both electron-donating and electron-withdrawing contaminants. The results revealed that the organic contaminants with electron-donating functional groups like –OH, –NH2 and alkyl groups rather than electron-withdrawing functional groups like –NO2 were easier to be degraded without significant interference of co-existing anions. Furthermore, Rhodamine B (RhB) was adopted as a pollutant model to optimize the reaction conditions and explore the possible oxidative degradation mechanism. The RhB degradation efficiency was up to 100% within 40 min in the presence of 0.3 g/L BUC-100, 0.4 mM peroxymonosulfate (PMS) and LED UV light irradiation. According to the results of trapping experiments, electron spin resonance (ESR) characterization, and quantitative/qualitative experiments, it was found that 1O2 played the dominant role in organic pollutants decontamination, in which the self-reaction of SO5•− was the main source of 1O2.

Palladium-copper catalyzed decarboxylation/de-cycloalkanonylative coupling reaction to synthesize 9,9-diaryl-xanthenes

An efficient palladium-copper catalyzed regioselective C–C bond cleavage/C–H bond activation/C–C bond reformation reaction to synthesize 9,9-diaryl-xanthenes has been developed. A variety of 9,9-diaryl-xanthenes were synthesized in moderate to good yields by 9H-xanthene-9-carboxylic acid/2-(9H-xanthen-9-yl)-cycloketones and aromatics bearing electron-donating functional groups through the decarboxylation/de-cycloalkanonylative coupling reactions.

Intramolecular proton transfer reaction dynamics using machine-learned ab initio potential energy surfaces

Hydrogen bonding interactions, which are central to various physicochemical processes, are investigated in the present study using ab initio-based machine learning potential energy surfaces. Abnormally strong intramolecular O–H⋯O hydrogen bonds, occurring in β-diketone enols of malonaldehyde and its derivatives, with substituents ranging from various electron-withdrawing to electron-donating functional groups, are studied. Machine learning force fields were constructed using a kernel-based force learning model employing ab initio molecular dynamics reference data. These models were used for molecular dynamics simulations at finite temperature, and dynamical properties were determined by computing proton transfer free-energy surfaces. The chemical systems studied here show progression toward barrier-less proton transfer events at an accuracy of correlated electronic structure methods. Markov state models of the conformational states indicate shorter intramolecular hydrogen bonds exhibiting higher proton transfer rates. We demonstrate how functional group substitution can modulate the strength of intramolecular hydrogen bonds by studying the thermodynamic and kinetic properties.

Effect of molecular structure on the adsorption behavior of sulfanilamide antibiotics on crumpled graphene balls

Since the 1930s, sulfonamide(SA)-based antibiotics have served as important pharmaceuticals, but their widespread detection in water systems threatens aquatic organisms and human health. Adsorption via graphene, its modified form (graphene oxide, GO), and related nanocomposites is a promising method to remove SAs, owing to the strong and selective surface affinity of graphene/GO with aromatic compounds. However, a deeper understanding of the mechanisms of interaction between the chemical structure of SAs and the GO surface is required to predict the performance of GO-based nanostructured materials to adsorb the individual chemicals making up this large class of pharmaceuticals. In this research, we studied the adsorptive performance of 3D crumpled graphene balls (CGBs) to remove 10 SAs and 13 structural analogs from water. The maximum adsorption capacity qm of SAs on CGB increased with the number of (1) aromatic rings; (2) electron-donating functional groups; (3) hydrogen bonding acceptor sites. Furthermore, the CGB surface displayed a preference for homocyclic relative to heterocyclic aromatic structures. A leading mechanism, π-π electron-donor-acceptor interaction, combined with hydrogen bonding, explains these trends. We developed a multiple linear regression model capable of predicting the qm as a function of SA chemical structure and properties and the oxidation level of CGB. The model predicted the adsorptive behaviors of SAs well with the exception of a chlorinated/fluorinated SA. The insights afforded by these experiments and modeling will aid in tailoring graphene-based adsorbents to remove micropollutants from water and reduce the growing public health threats associated with antibiotic resistance and endocrine-disrupting chemicals.

Expedient Synthesis of Dihaloalkenynes via Pd-Catalyzed Haloalkynylation Reaction.

Herein, the PdII -catalyzed construction of functionalized dihaloalkenynes from haloalkynes via a self-haloalkynylation reaction, without specialized ligands or oxidizing additives, is reported. The method tolerates a diverse range of haloalkynes, including electron-donating and electron-withdrawing functional groups, such as macrocyclic alkynols, spiro-oxy ring alkynols, and even carbazole-containing, pyrrolidine-2,5-dione-containing and silyl-protected bromoalkynes. Using an opposite lithium halide (LiX) to the haloalkyne starting material, remarkably high regio- and stereoselectivity of the haloalkynylation reaction is possible, yielding 1-bromo-2-chloroalkenyne or 2-bromo-1-chloroalkenyne products as desired.

Porphyrin-Based Covalent Organic Frameworks Anchoring Au Single Atoms for Photocatalytic Nitrogen Fixation

The development of efficient photocatalysts for N2 fixation to produce NH3 under ambient conditions remains a great challenge. Since covalent organic frameworks (COFs) possess predesignable chemical structures, good crystallinity, and high porosity, it is highly significant to explore their potential for photocatalytic nitrogen conversion. Herein, we report a series of isostructural porphyrin-based COFs loaded with Au single atoms (COFX-Au, X = 1-5) for photocatalytic N2 fixation. The porphyrin building blocks act as the docking sites to immobilize Au single atoms as well as light-harvesting antennae. The microenvironment of the Au catalytic center is precisely tuned by controlling the functional groups at the proximal and distal positions of porphyrin units. As a result, COF1-Au decorated with strong electron-withdrawing groups exhibits a high activity toward NH3 production with rates of 333.0 ± 22.4 μmol g-1 h-1 and 37.0 ± 2.5 mmol gAu-1 h-1, which are 2.8- and 171-fold higher than that of COF4-Au decorated with electron-donating functional groups and a porphyrin-Au molecular catalyst, respectively. The NH3 production rates could be further increased to 427.9 ± 18.7 μmol g-1 h-1 and 61.1 ± 2.7 mmol gAu-1 h-1 under the catalysis of COF5-Au featuring two different kinds of strong electron-withdrawing groups. The structure-activity relationship analysis reveals that the introduction of electron-withdrawing groups facilitates the separation and transportation of photogenerated electrons within the entire framework. This work manifests that the structures and optoelectronic properties of COF-based photocatalysts can be finely tuned through a rational predesign at the molecular level, thus leading to superior NH3 evolution.

Formation of Dichlorine Monoxide for Organic Pollutant Degradation by Free Chlorine in High Chloride-Containing Water

Several ppm levels of free chlorine in high chloride-containing water of no less than 0.20 M show remarkably high degradation rate constants toward carbamazepine (kCBZ′). Dichlorine monoxide (Cl2O) was identified to be responsible for the high kCBZ′. Cl2O degrades aromatic pollutants connected to more electron-donating functional groups faster when comparing kCl2O to 1,4-dimethoxybenzene, bisphenol A, benzoic acid, and CBZ. However, its formation at low free chlorine levels in high chloride-containing water cannot be explained by our current knowledge. We proposed an alternative Cl2O formation mechanism, in which chloride transforms hypochlorous acid/hypochlorite (HOCl/ClO–) to dichlorine (Cl2) and polychloride monoanions (Cln–), which then react with HOCl/ClO– to form Cl2O. Decreasing pH from 8.60 to 4.33 increases Cl2 concentrations and thus generates about 600× higher Cl2O concentrations. Weak acid anions, for example, phosphate and bicarbonate, are strong nucleophiles assisting the Cl2O hydrolysis, but their presence at the testing conditions does not much affect kCBZ′. The proposed alternative Cl2O formation mechanism reveals the roles of chloride in shifting the equilibrium toward the Cl2O formation, allowing the simple chlorine addition strategy to degrade recalcitrant organic pollutants in high chloride-containing wastewater. It may also change our understanding of the speciation of different free chlorine species and their impacts on the DBP formation in high chloride-containing wastewater.

Mononuclear discrete Ag(I) complexes of aryl substituted (E)-N-phenyl-1-(pyridin-3-yl)methanimine: In vitro biological activities and interactions with biomolecules

The synthesis of three pyridinyl imines (L1-L3) with electron-donating and electron-withdrawing functional groups, as well as their silver(I) complexes (1a-3a, 1b-3b and 1c-3c), resulted from our ongoing search for novel metallodrugs with potential pharmacological activity. Various analytical and spectroscopic analyses were used to characterize the Ag(I) complexes. The single crystal X-ray diffraction analysis of complexes 3a and 3b in the solid state confirmed their linear geometry around the Ag(I) center. In vitro antibacterial properties of the complexes evaluated using the minimum inhibitory concentration (MIC) method revealed that complexes containing either a Me- or an F-substituent exhibited greater activity. The ferric-reducing antioxidant power (FRAP) experiment revealed that complexes with hydroxyl substituents have high antioxidant potential. These complexes with IC50 values ranging from 0.86 to 2.47 mg mL-1 outperformed ascorbic acid, with an IC50 of 2.68 mg mL-1. The reported complexes bound to CT-DNA via intercalation mode with significant binding constants for complexes whose ligands bore the OH- substituent. Bovine serum albumin (BSA) binding affinity to the complexes ranges from moderate to high. The studied complexes with methyl substituents are promising anti-cervical cancer candidates.

Efficient and Moisture-Stable Inverted Perovskite Solar Cells via n-Type Small-Molecule-Assisted Surface Treatment.

Defect states at the surface and grain boundaries of perovskite films have been known to be major determinants impairing the optoelectrical properties of perovskite films and the stability of perovskite solar cells (PeSCs). Herein, an n-type conjugated small-molecule additive based on fused-unit dithienothiophen[3,2-b]-pyrrolobenzothiadiazole-core (JY16) is developed for efficient and stable PeSCs, where JY16possesses the same backbone as the widely used Y6but with long-linear n-hexadecyl side chains rather than branched side chains. Upon introducing JY16into the perovskite films, the electron-donating functional groups of JY16passivate defect states in perovskite films and increase the grain size of perovskite films through Lewis acid-base interactions. Compared to Y6, JY16exhibits superior charge mobility owing to its molecular packing ability and prevents decomposition of perovskite films under moisture conditions owing to their hydrophobic characteristics, improving the charge extraction ability and moisture stability of PeSCs. Consequently, the PeSC with JY16shows a high power conversion efficiency of 21.35%, which is higher than those of the PeSC with Y6 (20.12%) and without any additive (18.12%), and outstanding moisture stability under 25% relative humidity, without encapsulation. The proposed organic semiconducting additive will prove to be crucial for achieving highly efficient and moisture stable PeSCs.

Acridine yellow G (AYG) as a photo-induced electron transfer (PET) photocatalyst employed for the radical Michael-Mannich cyclocondensation of imines.

A four-component domino Michael–Mannich cyclocondensation of amines, dialkyl acetylenedicarboxylaes, and formaldehyde was utilized to develop a green technique for sans metal combination of polyfunctionalized dihydro-2-oxypyrroles. It involves visible light as an environmentally friendly power source and acridine yellow G (AYG) as a photo-induced electron transfer (PET) photocatalyst. The motivation behind this examination was to expand the utilization of a non-metal dye that is both reasonable and broadly accessible. Photochemically catalyzed AYG flaunts exceptional returns, energy effectiveness, and natural agreeableness, as well as extraordinary iota economy, efficient highlights, and comfort of purpose. Key abilities consist of an easy experimental setup, big substrate tolerance, finance-friendly, clean painting-up strategies within the absence of tedious separation techniques, and minimized the quantity of waste for each organic transformation. The type of yields is pretty uniform (85–97%, average 92.09%), and the shape of reaction times might be very speedy (15–30 min, average 21.59 min), and the factor stated inside the dialogue is that the method tolerates quite a number electron-donating and electron-withdrawing functional groups, while, however, giving extremely good yields. The response within the reason is insensitive to the person of the substituents. Subsequently, many compounds and natural factors can be followed over the course of time. Shockingly, gram-scale cyclization is conceivable, proposing that the strategy could be utilized in industry.

Screening of the Role of the Chemical Structure in the Electrochemical Stability Window of Ionic Liquids: DFT Calculations Combined with Data Mining.

Ionic liquids have attracted the attention of researchers as possible electrolytes for electrochemical energy storage devices. However, their properties, such as the electrochemical stability window (ESW), ionic conductivity, and diffusivity, are influenced both by the chemical structures of cations and anions and by their combinations. Most studies in the literature focus on the understanding of common ionic liquids, and little effort has been made to find ways to improve our atomistic understanding of those systems. The goal of this paper is to explore the structural characteristics of cations and anions that form ionic liquids that can expand the HOMO/LUMO gap, a property directly linked to the ESW of the electrolyte. For that, we design a framework for randomly generating new ions by combining their fragments. Within this framework, we generate about 104 cations and 104 anions and fully optimize their structures using density functional theory. Our calculations show that aromatic cations are less stable ionic liquids than aliphatic ones, an expected result if chemical rationale is used. More importantly, we can improve the gap by adding electron-donating and electron-withdrawing functional groups to the cations and anions, respectively. The increase can be about 2 V, depending on the case. This improvement is reflected in a wider ESW.

Nickel(II) complex anchored on MCM-41, a reusable catalyst for the synthesis of benzimidazole and quinazolinone

The Ni(II) complex of N2,N6-bis(3-(triethoxysilyl)propyl)pyridine-2,6-dicarboxamide (PDCA) has been prepared in situ and immobilized on MCM-41 to prepare a heterogeneous catalyst. Techniques such as FT-IR, low angle powder XRD, TGA, SEM, TEM, MP-AES, and N2 sorption studies were used for characterization of the isolated heterogeneous catalyst, MCM-41@PDCA-Ni. MCM-41@PDCA-Ni was used for the synthesis of benzimidazoles and quinazolinones in coupling reaction of substituted benzaldehyde with o-phenylenediamine and anthranilamide, respectively. The new catalyst showed tolerance towards both electron-withdrawing and electron-donating functional groups present in benzaldehyde. The high yield, easy recovery, and reusability for five times without significant loss in catalytic efficiency are the main advantages of MCM-41@PDCA-Ni.