Electron-donating Effect Research Articles

μ-nitrido diiron phthalocyanines: Electron-withdrawing vs electron-donating substituent effect on oxidation reaction catalysis

μ-nitrido diiron phthalocyanines: Electron-withdrawing vs electron-donating substituent effect on oxidation reaction catalysis

Glutathione-activated near-infrared II fluorescent probe for lung metastatic diagnosis and intraoperative imaging of tumor

Accurate identification of intraoperative tumor lesions and effective treatment are crucial for improving surgical outcomes. Near-infrared (NIR) fluorescence imaging demonstrates advantages over traditional medical approaches in tumor interventions, garnering significant attention. However, clinically available imaging agents are generally limited by their "always on" characteristics, which can lead to non-specific imaging interference and "false-positive" results. In this context, we present a glutathione-activated NIR-II probe, LJ-GSH, designed for metastatic tumor imaging and specific imaging-guided tumor resection. LJ-GSH initially exhibits quenched fluorescence due to the weak electron-donating effect of the thiophenol moiety, which is recovered at 815/910 nm upon activation by the overexpressed levels of glutathione (GSH) in tumor cells and tissues, significantly enhancing the specificity of tumor imaging. This unique characteristic positions LJ-GSH as a reliable fluorescent sensor for monitoring GSH dynamics during physiological events. Notably, the probe's NIR-II emission feature markedly improves imaging contrast and resolution, facilitating real-time identification and imaging of lung metastatic lesions. With the aid of high-specific NIR-II imaging guidance, tumor tissues can be precisely resected, with the residual negative margin diameter reduced to approximately 0.2 mm. We envision that our tailored probe may offer an attractive option for clinical applications.

Molecular engineering in thizolo[5,4-d]thiazole-based donor-acceptor covalent organic framework Induced high-efficient photosynthesis of H2O2

Covalent organic frameworks (COFs), as a newly emerging kind of porous and crystalline materials, serve as an ideal template for hydrogen peroxide (H2O2) photosynthesis. However, the vision of achieving high efficiency and selectivity in H2O2 photosynthesis is greatly hindered by the large exciton binding energy and limited charge separation efficiency influenced by the molecular structure of the building blocks. Herein, we developed three newly designed COFs with a donor–acceptor (D-A) structure and incorporated regulatory units (fluorine, F, and methoxyl, OCH3) in the D-A pathway through molecular engineering to optimize electronic structure, the availability of activate sites, charge kinetics and O2 activation capacity. Due to electron-donating effect, OCH3-functionalization (NIES-COF-3) can strengthen the intramolecular electron transfer and interaction with O2. This results in a reduction of the energy barrier of the rate-determining step (*O2 → *OOH) and excellent O2-to-H2O2 photocatalytic activity under visible light irradiation, delivering an H2O2 production rate of 3238.4 μmol g−1h−1 and a high apparent quantum yield of 3.17 %. In addition, F-functionalization (NIES-COF-2) primarily reduces the band-gap energy and improve the O2 adsorption capacity compared to unfunctionalized NIES-COF-1. This work unveils insight into the catalytic activity-optimization mechanism of molecular engineering in the D-A structure and provides important references for photocatalysts.

Water-Induced Switching in Selectivity and Steric Control of Activity in Photochemical CO2 Reduction Catalyzed by RhCp*(bpy) Derivatives.

Photocatalytic reduction of CO2 to formic acid (HCOOH) was investigated in either organic or aqueous/organic media by employing three water-soluble [RhIIICp*(LH2)Cl]+ (LH2 = n,n'-dihydroxy-2,2'-bipyridine; n = 4, 5, or 6) in the presence of [Ru(bpy)3]2+, 1,3-dimethyl-2-phenyl-2,3-dihydro-1H-benzo[d]imidazole (BIH) and triethanolamine (TEOA). Through studying the electron-donating effects of two hydroxyl groups introduced into the bipyridyl ligand, we found that the substituent positions greatly affect both the catalytic efficiency and selectivity in CO2 reduction. More importantly, the HCOOH selectivity shows a dramatic increase from 14 to 83% upon switching the solvent media from pure organic to an aqueous/organic mixture, where the H2 selectivity shows a reverse phenomenon. The enhanced HCOOH selectivity and the drastic decrease in the H2 yield are well rationalized by the fact that the catalytic CO2 hydrogenation is not only driven photochemically via the attack of RhIII(H)Cp*(LH2-·) on CO2 but also partly bypassed by a dark H2 addition reaction yielding [RhIII(H)Cp*(L)]- from [RhIIICp*(L)Cl]+, which was also separately investigated under dark conditions. A combination of experimental and theoretical approaches was made to clarify the pKa values of catalyst intermediates together with the abundant species responsible for the major catalytic processes. Our DFT studies unveil that the exceptionally large structural strain given by the steric contacts between the 6,6'-dihydroxyl groups and the Cp* moiety plays a significant role in bringing about an outstanding catalytic performance of the 6,6'-substituted derivative. The intrinsic reaction coordinate calculations were carried out to clarify the mechanism of hydride transfer steps leading to generating formate together with the heterolytic H2 cleavage steps leading to afford the key hydridorhodium intermediates. This study represents the first report on the water-induced high selectivity in CO2-to-HCOOH conversion, shedding new light on the strategy to control the efficiency and selectivity in the catalysis of CO2 reduction.

Synthesis, spectroscopic characterization techniques of aromatic iminoaniline derived compound, along with the evaluation of its LNO properties using quantum chemistry

In this research work, we synthesized a Schiff base derivative, N,N-dimethyl-4-{[(4-nitrophenyl)imino]-methyl}aniline, denoted as (n1). The molecule (n1) was characterized using spectroscopic analyses, including FT-IR, NMR 1H, and 13C. Our compound (n1) is an unsaturated molecule, consisting of two benzylic rings connected by a methylimine bridge. The resulting system comprises seven alternating π bonds. At both ends of (n1) and in the para position, there are the N(CH3)2 group with a strong electron-donating effect and the NO2 group with a strong electron-accepting effect. The molecular structure of our compound prompted us to evaluate and study its properties in the field of NLO. The assessment of NLO properties is conducted by determining the Egap and employing density functional theory (DFT) quantum chemistry studies. The optical gap of (n1), measured using the Tauc method, is found to be 2.7 eV, serving as a reference value for the choice of the DFT functional in theoretical calculations. Quantum chemistry studies were carried out using Gaussian09 software, and the results were visualized with GaussView05. CAM-B3lyp functional was chosen for theoretical calculations due to its close agreement with experimental values. The studies confirm that (n1) exhibits significant NLO properties. Additionally, NBO (Natural Bond Orbital) analyses provide insight into the mechanism and trajectory of intramolecular charge transfer in (n1).

Chemical Synthesis of Conjugation-Ready Trisaccharides Corresponding to Biological Repeating Units of Pseudomonas aeruginosa Serotype 10 and 19 O-Antigens.

Here we report the chemical synthesis of conjugation-ready trisaccharides, representing biological repeating units of Pseudomonas aeruginosa serotype 10 and 19 O-antigens. The α-d-QuiN3 glycosidic bond was stereoselectively synthesized through TMSI─Ph3P═O mediated 1,2-cis glycosylation. Selective oxidation of the C6-OH group at the disaccharide stage allowed for benzylidene-promoted construction of the α-l-GalN3 glycosidic bond and simplification of the postglycosylation process at the trisaccharide stage. The low reaction temperature and neighboring electron-donating effect facilitated the efficient synthesis of the trisaccharide.

Preparation of Red-Emitting CDs for Glioma Imaging and Fe3+ Sensing.

Red-emitting fluorescent carbon dots (CDs) have garnered significant attention due to their wide-ranging applications in biological fields. However, challenges such as complex precursors, labor-intensive preparation processes, and low quantum yields have hindered their broader utilization. In this study, we developed a simple and efficient solvothermal method to synthesize fluorescent CDs with tunable emission wavelengths using aniline derivatives as precursors. The emission wavelengths of the synthesized CDs were influenced by the functional groups at the para-position of the aniline derivatives with stronger electron-donating effects leading to a red shift in emissions. Notably, bright red-emitting CDs with a quantum yield of 19.42% and excellent photobleaching resistance were obtained by using p-phenylenediamine as the sole precursor. These CDs exhibited sensitivity to Fe3+ ions, demonstrating a strong linear detection range (R 2 = 0.999) from 0 to 50 μM. Additionally, the CDs were uniform in size (2-5 nm), emitted stable red fluorescence in pH conditions ranging from 4 to 10, and were successfully internalized by glioma cells, enabling precise fluorescence imaging of gliomas both in vitro and in vivo.

Bifunctional MoNi4/Nickel Foam Electro-Catalyst for Ultra-Efficient Oxidation of High-Concentration 5-Hydroxymethylfurfural and HER.

The electro-catalytic oxidation of biomass-derived 5-hydroxymethylfurfural (HMF) provides an attractive route to produce 2, 5-furandicarboxylic acid (FDCA) as a substitute for terephthalic acid used in the plastics industry. Herein, we prepared MoNi4 alloy on nickel foam (NF) using a simple hydrothermal method followed by hydrogen reduction. Applied MoNi4/NF as the bifunctional electrodes for the electro-catalytic HMF oxidation reaction (HMFOR) and HER, 98.7 % FDCA yield and 97.3 % Faraday efficiency (FE) can be achieved even with HMF concentration as high as 200 mM. Notably, no obvious deactivation was observed after ten consecutive cycles. In-situ Raman, XANES and EXAFS results show that the nickel species of MoNi4/NF is first oxidized to Ni3+ species under the applied voltage, and after undergoing the electro-catalytic HMFOR, then reduced to Ni2-δ state (with a valence between 0 and +2) due to the electron-donating effect from Mo. MoNi4/NF with more than one electron transfer between Ni3+ and Ni2-δ during the HMFOR enables it to have excellent electro-catalytic oxidation ability toward HMFOR.

New blue emitters based on anthracene through charge transfer control

We designed new moieties with varying electron-donating effects and sizes based on diphenylamine and introduced them into anthracene to synthesize three types of emitting materials. All three materials exhibited high thermal stability with glass transition temperatures above 175°C, confirming their potential as OLED emitters. Devices doped with N9,N9,N10,N10-tetraphenylanthracene-9,10-diamine (TAD), where diphenyl amine is substituted on both sides, and N9,N10-di([1,1′-biphenyl]-4-yl)-N9,N10-bis(dibenzo[b,d]furan-2-yl)anthracene-9,10 diamine (ABFA), with a fused side group of diphenyl amine and dibenzofuran, showed EQEs of 1.28 % and 3.57 % respectively. Due to the intramolecular charge transfer (ICT), they exhibited ELmax values at 517 nm and 538 nm. On the other hand, the device doped with N,N′-(anthracene-9,10-diylbis(4,1-phenylene))bis(N-([1,1′-biphenyl]-4-yl)dibenzo[b,d]furan-2-amine) (APBFA), which has optimized side groups that suppress ICT and intermolecular packing, achieved a relatively high EQE of 4.48 % and showed blue emission with CIE coordinates of (0.146, 0.142).

The Effects of Internal Electron Donors on MgCl2-Supported Ziegler–Natta Catalysts for Isotactic PP

The electron donors (ED) in Ziegler–Natta (Z-N) catalysis are classified as internal electron donors (IED) and external electron donors (EED), and both IED and EED are indispensable components for enhancing the catalytic reactivity and regulating the stereoregularity of polyolefinic materials in a typical industrial Z-N catalytic process. With the intensive research on ED, the Z-N catalyst performances have experienced successive progress in the last few decades. Polypropylenes (PP) as a commodity polyolefin material, especially the isotactic PP (iPP), are produced in multi-billion pounds per annum by utilization of the various IED- and EED-assisted Z-N catalysts systems. In the course of developing Z-N catalysts, the ED constitutes a key component of the content and represents a significant area of future research. In this review, we introduced a concise overview of the functions of IEDs in the generations of Z-N catalyst systems and the widely used IED types (A total of 11 different types of IEDs are encompassed within this study) that have been developed so far. In addition, we focused on the coordination modes of different IEDs in the MgCl2-supported Z-N catalyst system and analyzed the effects of different types of IEDs on the PP isotacticity, regioselectivity, hydrogen sensitivity, and briefly introduced the application of environmentally friendly rosinate and salicylate IEDs.

Design, synthesis, biological evaluation and molecular docking study of thiadiazole-isatin hybrid analogues as potential anti-diabetic and anti-bacterial agents

We have synthesized thiadiazole-isatin hybrid analogues (1–20), characterized through different spectroscopic techniques such as 1HNMR, 13CNMR, HREI-MS, and evaluated against α-glucosidase and α-amylase enzymes. All analogues showed potent inhibitory potentials, having an IC50 values ranged from 22.08 ± 0.09 to 54.03 ± 0.07 μM (against α-amylase) and 19.03 ± 0.04 to 50.03 ± 0.02 μM (α-glucosidase) when compared with the standard drug acarbose (IC50 = 22.07 ± 0.02 μM for α-amylase and IC50 = 18.01 ± 0.06 μM for α-glucosidase respectively). Among the series, analogues 13 (IC50 = 19.03 ± 0.04 and 22.08 ± 0.09 μM), 12 (IC50 = 21.03 ± 0.07 and 24.03 ± 0.07 μM), and 5 (IC50 = 22.02 ± 0.03 and 26.02 ± 0.04 μM) were identified as the most active inhibitors. The structure–activity relationship was carried out, mainly associated with the nature, number, position, and electron-donating and electron-withdrawing effects of the substituent (s) on the phenyl ring. With the help of molecular docking, the binding interaction of the most active analogues within the active site of enzymes was confirmed. Almost twelve compounds were also screened for antibacterial potential, and few were found to be effective against Bacillus subtilis. All compounds were verified for cytotoxicity against the 3 T3 mouse fibroblast cell line and detected non-toxic.

Electron Sponge Effect by Dynamic-Regulated Electron Self-Flow toward Coupled Electrochemical Ammonia Synthesis.

A dynamic-regulated Pd-Fe-N electrocatalyst was effectively constructed with electron-donating and back-donating effects, which serves as an efficient engineering strategy to optimize the electrocatalytic activity. The designed PdFe3/FeN features a comprehensive electrocatalytic performance toward the nitrogen reduction reaction (NRR, yield rate of 29.94 μg h-1 mgcat-1 and FE of 38.43% at -0.2 V vs RHE) and oxygen evolution reaction (OER, 308 mV at 100 mA cm-2). Combining in situ ATR-FTIR, XAS, and DFT results, the role of the interstitial-N-dopant-induced electron sponge effect has been significantly elucidated in strengthening the electrocatalytic NRR process. Specifically, the introduction of a N dopant, an electron acceptor, initiates the generation of robust Lewis-acidic Fe sites, facilitating free N2 capture and bonding. Simultaneously, after NH3 adsorption, the N dopant can back-donate electrons to Fe sites, strengthening the NH3 deportation through weakening the Lewis acidity of Fe centers. Besides, the electron-deficient Fe sites contribute to the reconstruction of FeOOH, the real active species during the OER, which accelerates the four-electron reaction kinetics. This research offers a perspective on electrocatalyst design, potentially facilitating the evolution of advanced material engineering for efficient electrocatalytic synthesis and energy storage.

Exploring the DNA-binding and anticancer potential of polypyridyl ruthenium(II) complexes

Organometallic medicines based on ruthenium (Ru) have attracted interest as chemotherapeutic and bioimaging agents due to their low toxicity and superior physical optical characteristics. However, there are still no ideal candidates in clinical trials due to the lack of understanding of the structure-activity relationships (SARs) of polypyrodyl Ru(II) complexes. Though increasing the electron-donating ability of the ligands has been proven to benefit bioactivity due to the fast hydroxylation rate between chlorine and DNA, the total electronic effects are much more important, especially for the binding modes between Ru(II)-polypyridyl complexes and DNA. By evaluating the electron-donating ability of the ligand complexes 1 - 4 through density functional theory (DFT) calculations, bioactivities tests, and docking studies, we investigated the relationship between the structures of Ru(II) complexes and cytotoxicity. Our findings showed that it was insufficient to merely consider the impact of electron-donating effects on biological activities in place of interaction modes. Furthermore, the cellular imaging study investigated the complex with phenyl substituents (1) and confirmed that the main target was DNA. Besides, the “off-on” emission phenomena of complex 1 indicated that there is also covalent interaction with DNA. These findings offer valuable insight into the development of SARs of polypyrodyl Ru(II) complexes.

Sonodynamic inactivation of gram-negative and gram-positive bacteria in the presence of phenothiazine compounds toluidine blue and azurin A

BackgroundSonodynamic antimicrobial chemotherapy (SACT) is an effective antimicrobial treatment that can avoid the production of drug-resistant bacteria. Design and development of new high-efficiency sonosensitizers play a key role in the practical application of SACT. MethodsThe bacteriostatic effects of two phenothiazine compounds, toluidine blue (TB) and azure A (AA) combined with ultrasonic (US) on Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were studied, and the sonodynamic antibacterial activities of TB and AA were compared. The reactive oxygen species (ROS) and the types of ROS produced in the sonodynamic system were detected and the sonodynamic mechanisms of TB and AA were proposed. ResultsThe sonodynamic bacteriostasis mediated by TB and AA increased with the increasing concentration of sonosensitizer, the extension of sonication time and the increase of reaction temperature. The production of ROS was the main reason that TB and AA had excellent sonodynamic antibacterial performance. Singlet oxygen (1O2) and hydroxyl radical (•OH) were the main ROS types in the sonodynamic antibacterial system. The ROS produced by the combined action of AA and US was higher than that of TB. ConclusionBoth TB and AA displayed excellent sonodynamic antibacterial activities. Moreover, AA had a higher sonodynamic activity than TB. The electron donation effect and steric hindrance effect of the methyl group of phenothiazine parent nucleus of TB might be the cause of the decrease of its sonodynamic activity. These results would provide a valuable reference for the further study of phenothiazines sonosensitizers and their clinical application in SACT.

Silicon Clathrate-Supported Catalysts with Low Work Functions for Ammonia Synthesis.

Diamond-type silicon has a work function of ≈4.8eV, and conventional n- or p-type doping modifies the value only between 4.6 and 5.05eV. Here, it is shown that the alkali clathrates AxSi46 have substantially lower work functions approaching 2.6eV, with clear trends between alkali electropositivity and clathrate cage size. The low work function enables alkali clathrates such as K8Si46 to be effective Haber-Bosch catalyst supports for NH3 synthesis. The catalytic properties of Si, Ge, and Sn-based clathrates are investigated while supporting Fe and Ru on the surface. The activity largely scales with the work function, and low activation energies below 60kJ mol-1 are observed due to strong electron donation effects from the support. Ru metal and Sn clathrates seem to be unsuitable for stability issues. Compared to other similar hydride/electride catalysts, the simple structure and composition combined with stability in air/water make a systematic study of these clathrates possible and open the door to other electron-rich Zintl phases and related intermetallics as low-work function materials suitable for catalysis. The observed low work function may also have implications for other existing electronic applications.

Enhanced peroxymonosulfate activation for emerging contaminant degradation via defect-engineered interfacial electric field in FeNC

Peroxymonosulfate (PMS) activation technology has important application value in treating emerging contaminant (ECs), but it still faces challenges in achieving efficient electron transfer and metal valence cycling. In this study, the interfacial electric field characteristics of FeNC catalysts were adjusted by introducing NC defects to affect the electron transfer process, thereby enhancing the catalytic performance of PMS. It is found that in the FeNC structure, the shift of the charge generates an interfacial electric field, which can promote the directional transfer of electrons. Through quantitative structure–activity relationship (QSAR) analysis, it was confirmed that the defect played a decisive role in regulating the interfacial electric field and improving the catalytic reaction efficiency. The interfacial electric field-mediated superexchange interaction realizes the electron donor effect of organic pollutants and the effective electron transfer between the Fe site, accelerates the electron cycling of the Fe site, and realizes the rapid and stable catalysis of PMS. The increase of the occupancy state distribution of d orbitals near the Fermi level provides favorable conditions for electron transitions and catalytic activation of PMS. ECs can be converted into environmentally friendly, non-toxic and harmless substances through. This defect-controlled interface electric field strategy realizes rapid electron directional transfer, which provides a new solution for improving the catalytic efficiency of PMS and the safe treatment of ECs in water.

A universal approach of constructing two-dimensional transition metal phosphide heterostructures and the superior performance in (urea-rich) water electrolysis

Transition metal phosphides have consistently shown excellent performance in electrocatalytic hydrogen production, but challenges remain in the development of efficient diverse catalysts. We designed a superhydrophilic two-dimensional (2D) TMP heterostructure with generalized approach. The phosphidation of layered double hydroxides (LDHs) with controlled exfoliation yielded multiple phosphide heterostructures (Ni2P/CoP, CoP/Fe2P and Ni2P/Fe2P) of less than 5 nm, the thinnest phosphide sheet up to date. All 2D phosphide heterojunctions are superhydrophilic (θw=10°), which is more favourable for bubble desorption. Both XPS and XANES, among other characterizations, indicated the much stronger electron-donating effect of metal sites comparing with bulk analogues, resulting in the formation of highly electron-rich P sites for facilitated proton adsorption. 2D Ni2P/CoP showed superior activity (η10=46.1 mV) for hydrogen production. Interestingly, 2D Ni2P/CoP was also highly active (η50=112.1 mV) for urea oxidation. This work demonstrates a versatile method for building superhydrophilic 2D phosphides, opening up exciting opportunities for multifunctional applications.

Achieving ultrahigh electrochromic stability of triarylamine-based polymers by the design of five electroactive nitrogen centers

A shortage of long-term stability of electrochromic materials has been hindering their practical application. A series of novel polyamides (PAs) (4) with five electroactive nitrogen atoms within triphenylamine (TPA)-containing structures was synthesized via phosphorylation polyamidation. Polyamide 4b exhibited highly integrated electrochromic performances, including multiple color changes, high contrast of optical transmittance change, and the highest electrochromic stability (only 11.2 and 9.6 % decay of its coloration efficiency (CE) at 450 nm after 50000 and 16000 switching cycles, respectively) compared to all other triarylamine-based polymers to date. This record-high electrochromic cycling is attributed to the enhanced stability of polaron, which was studied through the electron-donating or electron-withdrawing effect of substituents and the resonance effect of electron delocalization over the electroactive nitrogen centers. Importantly, our core design of five electroactive nitrogen centers with electron-donating methoxy groups is the key factor to increase stability of polaron in the resulting polymers 4. More electroactive nitrogen centers are able to create a weaker electronic coupling due to a charge of cation radical dispersed by resonance successfully in-between the different redox states, which is evidenced clearly by the observed longer wavelength absorption in the NIR region. Our research confirms that the key to determining polaron stability is the resonance by the electrons delocalized over all the redox centers, rather than the electronic coupling between the different redox centers. And the resonance leads to increasing electrochromic stability of the polymer.

Aromaticity of tropylium derivatives: When and why might captodative structures be preferred over the isomeric push‐pull structures?

AbstractAn intriguing question in the general problem of aromaticity is whether captodative aromatic systems with the donor and acceptor substituents at the same carbon of the CC bond can be more stable than the π‐conjugated push‐pull counterparts? The analysis of electronic, magnetic, and structural criteria of aromaticity showed that for conventional organic substituents XO, TfN, (NC)2C, (NO2)2C, Tf2C, the push‐pull tropylidene derivatives [tropylium]+CHCHX− are expectedly more stable than their captodative isomers [tropylium]+C(X−)CH2, with the lowest ΔE for the most strong acceptor Tf2C. A different behavior is observed for XMHlg3 (MB, Al; HlgF, Cl). They are not only structurally and magnetically most aromatic in both series but show the inverse stability of the push‐pull and captodative isomers, the latter being more stable by up to 10 kcal/mol (in gas).The difference between the MHlg3 groups and conventional organic groups is that in the latter the electron density is transferred to the π‐system of the substituent, while the former can accept it only to the σ*(CM) orbital. Thus, when the electron donor and acceptor effects are separated between the σ and π systems, captodative isomers can be more stable than their push‐pull isomers with more extended conjugation.

Introduction of Electron Donor Groups into the Azulene Structure: The Appearance of Intense Absorption and Emission in the Visible Region.

In this work, through the Suzuki-Miyaura cross-coupling reaction with high yields, new π-conjugated azulene compounds containing diphenylaniline groups at positions 2 and 6 of azulene were synthesized. The obtained diphenylaniline-azulenes have intensely visible-light absorbing and emitting (in the wavelength range from 400 to 600 nm) properties. It has been shown that such unique optical properties, in particular fluorescent emission in the region of blue and green photoluminescence (λem at 495 and 525 nm), which were absent in the original azulene, are the result of the electron donor effect of diphenylaniline groups, which significantly changes the electronic structure of azulene and leads to the allowed HOMO → LUMO electron transition.