Electron-donating Research Articles

The Impact of π-Bridge Moiety on the Optoelectronic Properties and Photochemical Stabilities of Benzodithiophene-Based Conjugated Polymers

The stability of conjugated polymers (CPs) under exposure to light and air determines their sustainability for commercial use and their possible usage in diverse areas. The main goal of this study is to examine how changes in the π-bridge of polymers affect their electrochemical and optoelectronic properties. Furthermore, it seeks to evaluate the impact of these alterations on the photochemical durability of the polymers. Three D-π-A types of CPs were synthesized via Stille coupling. All polymers consist of the same acceptor and donor units, which were benzooxadiazole (BOz) and benzo[1,2-b:4,5-b']dithiophene (BDT), respectively, but they had different π-bridge such as thiophene (T), selenophene (Se), and thiazole (Tz).This study used a variety of spectroscopic tools such as UV-Vis, FTIR, and XPS, to investigate how photooxidation occurs. DFT calculations were used to further support the experimental results. Within a mere 30-minute timeframe, the primary absorption peak of the polymer films experienced a blue shift and a significant reduction in intensity due to being exposed to both light and air simultaneously. Despite the presence of the same electron-withdrawing group, BOz, and electron-donating group, BDT, in all polymers, the photochemical stability varies with π-bridges. T- and Se-containing conjugated polymer films (P1-T, P2-Se) exhibited a significant decrease in the intensity of their peak absorption, whereas the peak intensity and characteristics of their thiazole counterpart (P3-Tz) only showed a slight alteration after being exposed to light and air for up to 7 hours. The superior photostability of the P3-Tz polymer film can be attributed to a significantly higher HOMO level and higher band gap in comparison to P1-T and P2-Se.Comprehending the photochemical stability of these polymers is crucial for progressing their commercial uses, such as organic photovoltaics, OLEDs, and sensors. This study highlights the significance of choosing suitable π-bridges to improve the longevity and effectiveness of CPs, thus satisfying market requirements and broadening their possible applications.

Electronic effect tuned ion-dipole interactions for low-temperature electrolyte design of LiFePO4-based lithium-ion batteries

Poor low-temperature performance is one of the major challenges hindering the widespread use of lithium-ion batteries. Modulation of Li+ solvation structure to facilitate desolvation process is an important strategy in electrolyte engineering under low temperature. Herein, different electronic effect groups including electron-withdrawing groups (CH2Cl) and electron-donating groups (CH3), are introduced in the weakly solvated solvent tetrahydrofuran (THF), respectively, to compare their effects on the ion-dipole interaction in the electrolyte and thus the regulation of Li+ solvation structure. Theoretical calculations combined with characterization demonstrates that the introduction of electron-withdrawing groups CH2Cl in the solvent can reduce the electron cloud density of oxygen in the THF solvent molecule, weaken the binding energy between Li+ and the solvent, and lead to more anions participating in solvation shell of Li+ and coordinating with Li+, thus accelerating the desolvation kinetics of Li+. This electrolyte-design strategy based on electronic effect tuned ion-dipole interactions has notably increased the cycling stability of the LiFePO4||Li half-cell at −20 °C, that is, it not only increases the capacity by about 10 mAh g−1 at the rate of 0.2 C, but also maintains the capacity retention rate at 97.4 % after 100 cycles. This study reveals an important electrolyte design strategy at the molecular level.

Advancements in Inverse-Electron-Demand Diels–Alder Cycloaddition of 2-Pyrones: Mechanisms, Methodologies

The Diels-Alder (DA) cycloaddition is well-known for its effectiveness in synthesizing natural products and multifunctional materials. This article specifically explores the inverse-electron-demand Diels-Alder (IEDDA) cycloaddition involving 2-pyrones, which display ambiphilic properties due to their unique electronic characteristics. We investigate the mechanisms underlying IEDDA, with a focus on how electron-donating and electron-withdrawing substituents influence reactivity and product selectivity. Various methodologies are reviewed, encompassing non-catalytic and catalytic approaches. Special attention is given to advancements in microwave-assisted techniques and high-pressure conditions, which enhance both reaction efficiency and selectivity. Additionally, the synthesis of chiral bridged bicyclic lactones from substituted 2-pyrones is examined, illustrating their versatility in organic synthesis. This review underscores the significance of IEDDA cycloaddition in pioneering new synthetic routes for building complex molecular structures.

Synthesis and Structure of Novel Hybrid Compounds Containing Phthalazin-1(2H)-imine and 4,5-Dihydro-1H-imidazole Cores and Their Sulfonyl Derivatives with Potential Biological Activities

A novel hybrid compound—2-(4,5-dihydro-1H-imidazol-2-yl)phthalazin-1(2H)-imine (5) was synthesized and converted into di-substituted sulfonamide derivatives 6a–o and phthalazine ring opening products—hydrazonomethylbenzonitriles 7a–m. The newly prepared compounds were characterized using elemental analyses, IR and NMR spectroscopy, as well as mass spectrometry. Single crystal X-ray diffraction data were collected for the representative compounds 5, 6c, 6e, 7g, and 7k. The antiproliferative activity of compound 5, sulfonyl derivatives 6a–o and benzonitriles 7a–m was evaluated on approximately sixty cell lines within nine tumor-type subpanels, including leukemia, lung, colon, CNS, melanoma, ovarian, renal, prostate, and breast. None of the tested compounds showed any activity against the cancer cell lines used. The antioxidant properties of all compounds were assessed using the DPPH, ABTS, and FRAP radical scavenging methods, as well as the β-carotene bleaching test. Antiradical tests revealed that among the investigated compounds, a moderate ABTS antiradical effect was observed for sulfonamide 6j (IC50 = 52.77 µg/mL). Benzonitrile 7i bearing two chlorine atoms on a phenyl ring system showed activity in a β-carotene bleaching test (IC50 = 86.21 µg/mL). Finally, the interaction AGE/RAGE in the presence of the selected phthalazinimines 6a, 6b, 6g, 6m, and hydrazonomethylbenzonitriles 7a, 7c–g, and 7i–k was determined by ELISA assay. A moderate inhibitory potency toward RAGE was found for hydrazonomethylbenzonitriles—7d with an electron-donating methoxy group (R = 3-CH3O-C6H4) and 7f, 7k with an electron-withdrawing substituent (7f, R = 2-Cl-C6H4; 7k, R = 4-NO2-C6H4).

Two-Dimensional Covalent Organic Frameworks with Carbazole-Embedded Frameworks Facilitate Photocatalytic and Electrocatalytic Processes

Catalytic technologies are pivotal in enhancing energy efficiency, promoting clean energy production, and reducing energy consumption in the chemical industry. The pursuit of novel catalysts for renewable energy is a long-term goal for researchers. In this work, we synthesized three two-dimensional covalent organic frameworks (COFs) featuring electron-rich carbazole-based architectures and evaluated their catalytic performance in photocatalytic organic reactions and electrocatalytic oxygen reduction reactions (ORRs). Pyrene-functionalized COF, termed as FCTD-TAPy, demonstrated excellent photocatalytic performance for amino oxidation coupling and showed a remarkable preference for substrates with electron-withdrawing groups (up to >99% Conv. and >99% Sel). Furthermore, FCTD-TAPy favored a four-electron transfer pathway during the ORR and exhibited favorable reaction kinetics (51.07 mV/dec) and a high turnover frequency (0.011 s−1). In contrast, the ORR of benzothiadiazole-based FCTD-TABT favored a two-electron transfer pathway, which exhibited a maximum double-layer capacitance of 14.26 mF cm−2, a Tafel slope of 53.01 mV/dec, and a hydrogen peroxide generation rate of 70.3 mmol g−1 h−1. This work underscores the potential of carbazole-based COFs as advanced catalytic materials and offers new insights into the design of metal-free COFs for enhanced catalytic performance.

Precise Single-Atom Modification of Hybrid Lead Chlorides for Electron Donor-Acceptor Effect and Enhanced Photocatalytic Aerobic Oxidation.

Hybrid lead halides show significant potential in photocatalysis due to their excellent photophysical properties, but the atomically precise modification of their organic component to achieve synergistic interactions with the lead halide units remains a great challenge. Herein, for the first time, we have employed the crystal engineering strategy to construct a class of single-atom-substituted hybrid lead halides with electron donor-acceptor (D-A) effect. The lead halide frameworks consist of 1D linear [PbCl]+ chains as inorganic building units and benzoxadiazole/benzothiadiazole/ benzoselenadiazole-funtionalized dicarboxylates as linkers. The covalent bonding between the organic ligands with electron-withdrawing groups and the electron-rich lead halide units not only facilitate the charge separation, but also enhance structural robustness that is critical for photocatalysis. The D-A structured lead halides serve as highly efficient heterogeneous photooxidation catalysts, including aerobic oxidation of C(sp3)-H bonds, oxidative coupling of primary amines, oxidation of phenylboronic acids and selective oxidation of sulfides that are demonstrated in 30 examples. Importantly, these photooxidation reactions are able to be driven by natural sunlight and ambient air to afford quantitative yields. Moreover, our lead halide photocatalysts are successful to fix into a photocatalytic flow system, which enables the flow-type synthesis of high value-added photooxidation products on a gram scale.

Sterically Hindered Derivatives of Pentacene and Octafluoropentacene.

6,13-Diethynylpentacene derivatives with sterically bulky substituents (Tr*, tris(3,5-di-tert-butylphenyl)methyl groups) appended to the ethynyl moieties at the 6- and 13-positions have been synthesized, as well as derivatives with electron-withdrawing fluorine groups on the 1,2,3,4,8,9,10,11-positions. These molecules are designed to investigate relationships between steric and electronic effects on the stability of pentacene toward endoperoxide formation via reaction with photosensitized oxygen in solution under ambient light (i. e., 'laboratory' conditions). It is evident from the study that stabilization through changes to the electronic characteristics of pentacene are more effective than the incorporation of sterically bulky groups at the acetylenic termini. Selected pentacene derivatives have been made into binary, amorphous films with the fullerene derivative PCBM to investigate the stability imparted by substituents against cycloaddition reactions. Overall, the introduction of steric protection through the incorporation of Tr* groups is not an efficient strategy for enhancing the persistence of pentacenes. Stabilization through fluorination proves successful for extending the lifetime of the pentacene derivatives by an order of magnitude in solution. Notably, the persistence of pentacene derivatives in solution can also be enhanced through the use of ethereal solvents stabilized with butylated hydroxy toluene (BHT) and/or an increased number of trialkylsilyl groups as substituents.

Tetracyanoethylene as a Building Block in the π-Expansion of 1,4-Dihydropyrrolo[3,2-b]pyrroles.

The outcome of the reaction of tetracyanoethylene with 1,4-dihydropyrrolo[3,2-b]pyrroles (DHPPs) strongly depends on the character of the substituents present at positions 2 and 5. With electron-withdrawing substituents, the reaction does not occur at all, while, in contrast, the presence of electron-donating substituents yields addition-elimination products. When thiazol-2-yl substituents are located at positions 2 and 5, addition occurs at the thiazole ring, rather than of the DHPP core. In cases where very electron-rich heterocycles are present at positions 2 and 5, a second addition occurs followed by aromatization, leading to the formation of an additional benzene ring bridging two heterocyclic scaffolds. The reaction occurs only at one site since the presence of the strongly electron-withdrawing tricyanoethylene group has a profound impact on electron density at the remaining free position 6. The DHPPs possessing a tricyanoethylene group are strongly polarized and thus enable a push-pull system showing red-shifted absorption and negligible fluorescence. In contrast, dyes possessing a 1,2-dicyanobenzene moiety exhibit strong emission bathochromically shifted by over 100 nm compared to parent 1,4-dihydrotetraarylpyrroles[3,2-b]pyrroles (TAPPs). Computational studies shed light on the evolution of the photophysical properties as a function of the substitution pattern of the final systems.

Photoinduced Zn-Air Battery-Assisted Self-Powered Sensor Utilizing Cobalt and Sulfur Co-Doped Carbon Nitride for Portable Detection Device.

Most self-powered electrochemical sensors (SPESs) are limited by low open circuit voltage and power density, leading to a narrow detection range and low sensitivity. Herein, a photoinduced Zn-air battery-assisted SPES (ZAB-SPES) is proposed based on cobalt and sulfur co-doped carbon nitride with the cyano group (Co, S-CN). The cyano functionalization remarkably enhances visible light utilization, and the cyano moiety acts as an electron-withdrawing group to promote electron enrichment. Co and S co-doping can create a p-n homojunction within carbon nitride, enabling the efficient migration and separation of carriers, thereby significantly improving the performance of the oxygen reduction reaction. The synergistic effects endow Co, S-CN photocathode with an open circuit voltage of 1.85V and the maximum power density of 43.5µW cm-2 in the photoinduced ZAB. Employing heavy metal copper ions as the target model, the photoinduced ZAB-SPES exhibited dual-mode and sensitive detection. Furthermore, a portable detection device based on the photoinduced ZAB-SPES is designed and exhibits high linearity in the range of 5 ~ 600nM with a detection limit of 1.7nM. This work offers a portable detection method based on the photoinduced ZAB-SPES in the aquatic environment.

Effect of Peripheral Functionalization of Pt(II) Porphyrin(2.1.2.1) on Singlet Oxygen Generation.

Four structurally bent porphyrin(2.1.2.1) Pt(II) complexes have been obtained and verified well. Main absorbance of Pt(II) porphyrin(2.1.2.1) displayed a significant red-shift compared to that of porphyrin(1.1.1.1) Pt(II) molecules. 1O2 study indicated that electron-withdrawing group and intramolecular charge transfer effect synergistically endowed Pt(II) porphyrin(2.1.2.1) with good singlet oxygen-sensitizing capacity under blue LED light irradiation. This work presents a simple synthesis way to develop a new series of efficient porphyrinoid singlet oxygen photosensitizers for PDT through molecular engineering.

Synthesis of Sulfonamide-Based Schiff Bases as Potent Anticancer Agents: Spectral Analyses, Biological Activity, Molecular Docking, ADME, DFT, and Pharmacophore Modelling Studies.

The current study focuses on the synthesis and characterization of six benzenesulfonamide-based Schiff base derivatives (7-12) with various electron-withdrawing and electron-donating substituents (-F, -CI, -Br, -CH3, and -OCH3) and the assessment of their antiproliferative activities against human lung (A549) and liver (HepG2) cancer cell lines using in vitro and in silico approaches. The structures of the synthesized compounds (7-12) were elucidated by elemental analysis and FT-IR, 1D (1H, 13C, APT, and DEPT-135), and 2D (HMQC and HMBC) NMR spectroscopies. The cytotoxic activities of the targeted compounds were determined at various concentrations against these cancer cell lines for 72 h, using the MTT method. The targeted molecules (7-12) demonstrated remarkable antiproliferative activities, with IC50 values ranging from 6.032-9.533 μM against the A549 cell line and 5.244-9.629 μM against the HepG2 cell line. These compounds showed activities at lower or very similar concentrations to cisplatin against the A549 cell line and at much lower concentrations than cisplatin against the HepG2 cell line. Among them, compounds 10 and 12 were found to be more effective against A549 and HepG2 cells, respectively, than cisplatin. These compounds were analyzed by interacting with the 1BNA, 4HJO, and 4ASD crystal structures in molecular docking studies.

Near-Infrared Room-Temperature Phosphorescence from Monocyclic Luminophores.

Compact luminophores with long emission wavelengths have aroused considerable theoretical and practical interest. Organics with room-temperature phosphorescence (RTP) are also desirable for their longer lifetimes and larger Stokes shifts than fluorescence. Utilizing the low electronic transition energy intrinsic to thiocarbonyl compounds, electron-withdrawing groups were attached to the 4H-pyran-4-thione core to further lower the excited state energies. The resulting mini-phosphors were doped into suitable polymer matrices. These purely organic, amorphous materials emitted near-infrared (NIR) RTP. Having a molar mass of only 162 g·mol-1, one of the phosphors emitted RTP that peaked at 750 nm, with a very large Stokes shift of 15485 cm-1 (403 nm). Thanks to the good processability of the polymer film, light-emitting diodes (LEDs) with NIR emission were easily fabricated by coating doped polymer on ultraviolet LEDs. This work provides an intriguing strategy to achieve NIR RTP using compact luminophores.

Novel Aminocoumarin-Based Schiff Bases: High Antifungal Activity in Agriculture.

Structural modification is an effective way to improve the antifungal activity of natural products and has been widely used in the development of novel fungicides. In this work, a series of aminocoumarin-based Schiff bases were synthesized and characterized by 1H-NMR, 13C NMR and HR-MS spectra. The in vitro inhibition activity of all compounds was tested against four phytopathogenic fungi (Alternaria solani, Fusarium oxysporum, Botrytis cinerea, and Alternaria alternata) using the mycelial growth rate method. The results showed that most of the target compounds exhibited significant antifungal activities. In particular, compounds 5b, 5c, 5d, 5h, 5n, 7c, 7n, and 7p exhibited more effective antifungal activity than commercially available fungicides, chlorothalonil and azoxystrobin. The structure-activity relationship revealed that the electron-withdrawing groups with more electronegativity introduced at the C-3 position were effective in improving the inhibitory activity and that halogenated benzaldehydes would be necessary in the preparation of Schiff bases. The compound 5n against Fusarium oxysporum (EC50=8.73 μg/mL) and the compound 7p against Alternaria alternata (EC50=26.25 μg/mL) were much better than the positive controls (chlorothalonil and azoxystrobin). Therefore, compounds 5n and 7p could serve as promising lead compounds for the development of novel broad-spectrum fungicides, which could be useful for applications in the agriculture.

Mixed-Linker Zr-Metal-Organic Framework with Improved Lewis Acidic Sites for CO2 Fixation Reaction Catalysis.

Applying the mixed-linker strategy in synthesizing metal-organic frameworks (MOFs) has drawn considerable attention as a heterogeneous catalyst owing to their easy synthesis and different functional ligands in their frameworks. Following this strategy, we have developed a mixed linker Zr(IV)-based MOF, [Zr6O4(OH)4(FUM)n(PZDC-NO2)6-n] (PZDC-NO2 = 4-nitro-3,5-pyrazoledicarboxylic acid, FUM = fumaric acid) denoted as MOF-801(PZDC-NO2) synthesized via this strategy which possess an electron-withdrawing group (-NO2) on secondary linkers. The MOF-801(PZDC-NO2) has been fully characterized via various analyses, such as Fourier transform infrared, powder X-ray diffraction, 13C/1H nuclear magnetic resonance, XPS, TGA, and N2 adsorption/desorption, SEM, EDX, etc. By considering the concurrent existence of acid-base active sites and the synergistic role of these sites, this mixed-linker MOF was used as a catalyst for the cycloaddition reaction of CO2 and epoxides under mild without-solvent conditions. MOF-801(PZDC-NO2) displays significant catalytic performance by producing the highest catalytic conversion of epoxide to cyclic carbonate (93%) with a turnover number of 130.7 in 8 h reaction time and 100 °C temperature under low-pressure CO2 pressure. The mixed-linker Zr-MOF exhibits exceptional stability and reusability, maintaining its structure and functionality after consecutive cycles of utilization. Finally, the reaction mechanism was further investigated by density functional theory calculations. The total energy of the reactants, intermediates, and products involved in the process.

Effects of functional groups on ESIPT and antioxidant activity of apigenin: A non-existent enol* state fluorescein

The development and enhancement of antioxidant drugs, which are aimed at mitigating DNA damage, mutations, and cancer, are of paramount significance in the biomedical sphere. In recent years, antioxidant drug molecules with photoluminescence have sprung up like mushrooms. Apigenin (AP), characterized by its distinctive property of excited state intramolecular proton transfer (ESIPT), plays a pivotal role in mediating antioxidant and anticancer activities. Despite being a representative molecule of the non-existent enol form (E*) state with ESIPT nature, there is a notable lack of theoretical investigations into its antioxidant properties. Herein, density functional theory (DFT) and time-dependent DFT methodologies were utilized to explore the effects of various functional groups on AP molecules in a methanol solvent. Studies have demonstrated that for the non-existent E* state fluorescence molecule AP, the ESIPT process can significantly enhance the antioxidant potency of AP and its derivatives. However, the introduction of electron-withdrawing groups significantly accelerated the ESIPT process while simultaneously suppressing the antioxidant activity of AP-CN. Conversely, the incorporation of electron-donating groups effectively inhibited the ESIPT process, yet markedly enhanced the antioxidant activity of AP-NH2. This investigation furnishes vital perspectives and sources of reference for the conception and advancement of groundbreaking antioxidant medications that aim to tackle non-existent E* state molecules.

Targeted Modulation of Photocatalytic Hydrogen Evolution Activity by Nickel-Substituted Rubredoxin through Functionalized Ruthenium Phototriggers.

Light-driven hydrogen evolution is a promising means of sustainable energy production to meet global energy demand. This study investigates the photocatalytic hydrogen evolution activity of nickel-substituted rubredoxin (NiRd), an artificial hydrogenase mimic, covalently attached to a ruthenium phototrigger (RuNiRd). By systematically modifying the para-substituents on Ru(II) polypyridyl complexes, we sought to optimize the intramolecular electron transfer processes within the RuNiRd system. A series of electron-donating and electron-withdrawing groups were introduced to tune the photophysical, photochemical, and electrochemical properties of the ruthenium complexes. Our findings reveal that electron-donating substituents can increase the hydrogen evolution capabilities of the artificial enzyme to a point; however, the complexes with the most electron-donating substituents suffer from short lifetimes and inefficient reductive quenching, rendering them inactive. The present work highlights the intricate balance required between driving force, lifetime, and quenching efficiency for effective light-driven catalysis, providing valuable insights into the design of artificial enzyme-photosensitizer constructs.

Molecular Unravelling of the Structural Effect of Quinone Redox Mediators on Oxygen Reduction Reaction in Aprotic Lithium-Oxygen Batteries.

Redox mediators (RMs) provide tantalizing solutions to unlock the energy capabilities of aprotic lithium-oxygen (Li-O2) batteries by driving solution-mediated Li2O2 growth. However, the structural effect of RMs on the catalytic efficiency of the oxygen reduction reaction remains incompletely understood. Herein, we present the interplay between the structure of RMs and their discharge capabilities by a comparative study of model quinone (Q)-based RMs. Specifically, at low current densities, incorporating electron-withdrawing groups onto the Q ring can positively move the discharge potential and deliver larger discharge capacity by extending the lifespan of the LiQO2 intermediate and allowing for Li2O2 growth into deeper electrolyte regions. Conversely, at high current densities, the absence of electron-withdrawing groups facilitates homogeneous reaction kinetics from LiQ to regenerate Q (i.e., decreased lifespan of LiQO2), mitigating electrode potential polarization and preserving catalytic activity of Q for higher discharge capacity. The work establishes structure-property relationships that guide the rational design of RMs toward next-generation Li-O2 batteries.

Donor-Acceptor Type Supra-Carbon-Dots with Long Lifetime Photogenerated Radicals Boosting Tumor Photodynamic Therapy.

Carbon dots (CDs) have gained significant interest because of their potential in biomedical applications. Nevertheless, developing CDs with efficient photoinduced charge separation for tumor photodynamic therapy (PDT) remains a challenge. This study presents a novel class of supra-carbon-dots (supra-CDs) developed by fusing red emissive CDs with 2,3-dicyanohydroquinone (DCHQ) via post-solvothermal treatment. In supra-CDs, the core, acting as electron donors, is formed by assembled CDs with substantial sp2 domains, the fused interface originating from DCHQ with electron-withdrawing groups functions as the electron acceptor. This configuration creates the unique donor-acceptor nanostructure. Upon white light irradiation, the excited electrons from the assembled CDs were transferred to the electron-withdrawing interface, whereas the photogenerated holes were retained within the assembled CDs as radicals, leading to effective photoinduced charge separation. The separated photogenerated electrons then react with oxygen to generate superoxide radicals. Simultaneously, the photogenerated holes undergo oxidation of crucial cellular substrates. This dual action underscores the exceptional cell-killing efficacy of supra-CDs. Moreover, the increased particle sizes (~20 nm) ensure supra-CDs to exhibit a notable capacity for tumor accumulation via the improved permeability and retention effect, thereby achieving satisfactory anti-tumor PDT efficacy in a mouse subcutaneous tumor model.

Selective Chromogenic Chemosensors for Arsenite Anion: A Facile Approach to Analyzing Arsenite in Honey, Milk, and Water Samples.

In this study, two chemosensors, N5R1 and N5R2, based on 5-(4-nitrophenyl)-2-furaldehyde, with varying electron-withdrawing groups, were synthesized and effectively employed for the colorimetric selective detection of arsenite anions in a DMSO/H2O solvent mixture (8 : 2, v/v). Chemosensors N5R1 and N5R2 exhibited a distinct color change upon binding with arsenite, accompanied by a spectral shift toward the near-infrared region (Δλmax exceeding 200 nm). These chemosensors established stability between a pH range 6-12. Among them, N5R2 displayed the lowest detection limit of 17.63 ppb with a high binding constant of 2.6163×105 M-1 for arsenite. The binding mechanism involved initial hydrogen bonding between the NH binding site and the arsenite anion, followed by deprotonation and an intramolecular charge transfer (ICT) mechanism. The mechanism was confirmed through UV and 1H NMR titrations, cyclic voltammetric studies, and theoretical calculations. The interactions between the sensor and arsenite anions were further analyzed using global reactivity parameters (GRPs). Practical applications were demonstrated through the utilization of test strips and molecular logic gates. Real water samples, honey, and milk samples were successfully analyzed by both chemosensors for the sensing of arsenite.

Cobalt(II) catalyzed Michael-type hydroamination of activated olefins

The aza-Michael addition reaction of primary and secondary amines to α,β-unsaturated olefins viz; acrylonitrile, phenyl vinyl sulfone and dimethyl maleate has been carried out using 5–10 mol% Co(NO3)2.6H2O as a catalyst in t-BuOMe at 80–100 °C, giving rise to the desired β-aminocarbonyl compounds or sulfones in moderate to good yields. A wide range of aromatic amines, even those bearing electron withdrawing groups could be added to activated olefins via this strategy. Addition of (hetero)aromatic amines were also feasible, while in case of 2-aminopyridine the reaction was found to be effective only when AgOTf was added along with the catalyst. The aliphatic amines; benzylamine, dibenzylamine, di-n-butylamine were also smoothly added to acrylonitrile and phenyl vinyl sulfone. The methodology describes cobalt(II) nitrate as an eco-friendly, cheap and shelf available catalyst suitable for performing the Michael-type hydroamination reactions.