Non-aqueous Environment Research Articles

Voltammetric detection of chlorogenic acid by Poly(3,4-ethylene-dioxythiophene) electrodes

This work aims at developing selective detection of chlorogenic acid (CGA), a critical phenolic acid related to the antioxidant level and taste of coffee, by a pristine poly(3,4-ethylenedioxythiophene) (PEDOT) electrode. The electrochemical oxidation of CGA on two types of PEDOT films, electrodeposited in aqueous (water, aq-PEDOT) and non-aqueous solvents (acetonitrile, ACN-PEDOT), were systematically studied and compared. Aq-PEDOT film showed a linear response for CGA in a range from 1.5 µM to 2.5 mM and a sensitivity of 0.33 mA/cm2⋅mM; ACN-PEDOT film showed a non-linear response with residual CGA. For repeated sensing purposes, we chose aq-PEDOT for the CGA sensor demonstration. Although cross-sensitivity with gallic acid (GA) and caffeic acid (CA) at 0.35 V was observed due to the shared catechol structure, selectivity for CGA determination against vanillin (VAN), guaiacol (GUA), theobromine (THB), theophylline (THP), quinic acid (QA), and caffeine (CAF) was confirmed. The distinct sensing behavior of the PEDOT films was further investigated: aq-PEDOT had a relatively flat surface and obeyed diffusion-controlled kinetics for CGA electro-oxidation. In contrast, ACN-PEDOT had a rougher coral-like morphology and strong adsorption characteristics. The measurements in real coffee samples by aq-PEDOT were also demonstrated with the interference from CA compensated. In brief, this study proves the niches and provides in-depth electrochemical kinetics for voltammetric CGA sensing using the PEDOT films prepared in aqueous and non-aqueous environments.

Naked eye detection of anions: Dihydrazone receptor-based visual sensing

In this study, we designed and synthesized a novel colorimetric sensor for fluoride ions by integrating a thienodicarbohydrazide framework with salicylaldehyde, resulting in a unique bis-hydrazone-phenol receptor. This sensor exhibited exceptional selectivity for fluoride and acetate ions in nonaqueous environments, with detection visible to the naked eye. Upon interaction with fluoride ions, the receptor underwent a significant red shift in its UV–Visible absorption spectrum, moving from an absorption maximum at 332 nm–380 nm, signalling the recognition event. Acetate ions induced a similar shift. The binding interactions were thoroughly investigated, with a Jobs plot revealing a 1:1 receptor-anion complex formation with fluoride ions and a 1:2 complex with acetate ions. Further validation came from 1H NMR titration, which confirmed the presence of hydrogen bonding interactions between the receptor and the ions. The receptor demonstrated remarkable binding constants of 5.2 × 10⁴ M−2 for acetate and 1.6 × 10⁴ M−1 for fluoride ions, highlighting its strong and selective affinity. Fluorescence titrations further confirmed the receptor's potential as a chemo sensor, showing distinct emission changes in the presence of fluoride and acetate ions. This study not only underscores the receptor's capability for visual detection of fluoride ions in non-aqueous systems but also paves the way for its application in diverse analytical and environmental settings.

Electrochemical Reactivity of Hydrogen Storage Materials: Exploring Borohydride and Hydrazinium Salt Mixtures

Electrochemical characterization of hydrogen storage materials was conducted in a non-aqueous environment to investigate the direct electrochemical release and consumption of hydrogen and the potential for regeneration. We first address the challenge of minimal solubility of the synthetic precursors, sodium borohydride (NaBH4) and hydrazinium bromide (N2H5Br), in both organic and inorganic solvents. We next determine and calibrate a reference electrode formulation compatible with our non-aqueous media and analytes that demonstrates a stable reference potential. We employ cyclic voltammetry (CV) to characterize the precursors and mixtures thereof. Each CV peak is assigned to a corresponding electrochemical reaction. Using the rate-dependent CV method and Randles–Ševčík equation, we calculate the diffusion coefficient of each chemical (NaBH4 and N2H5Br). Analysis of the CVs, coupled with 11B NMR analysis, reveals a room temperature chemical transformation of NaBH4 and N2H5Br mixtures into hydrazine borane (N2H4BH3). These results are particularly significant, considering the limited information available on the electrochemical characterization of metal borohydride and hydrazinium salt in non-aqueous media. This work establishes a foundation for adapting a non-aqueous electrochemical system to further study the borohydride family of chemistries and to design and develop electrochemical devices for direct electrical and chemical energy interconversion with hydrogen storage materials.

An azine‐based halochromic molecular chameleon

Halochromism has a plethora of uses in the textile industry, including wound treatments and protective apparel. Reactive dye’s fastness and a wide variety of hues, from bright to dull, make it ideal for coloring cotton and other regenerated cellulose fibers. It is also fundamentally paramount importance to determine the freshness of packaging foods. In this study, a halochromic probe, 4,4′-((1E,1′E,3E,3′E)-hydrazine-1,2-diylidenebis(prop-1-en-1-yl-3-ylidene))bis(N, N-dimethylaniline), HDBD, has been introduced utilizing a simple condensation reaction. Through the protonation and deprotonation process with the addition of acid and base in the non-aqueous medium, HDBD shows visual colorimetric as well as ratiometric UV–visible absorption spectral change. A colorimetric paper strip-based experiment has been demonstrated to detect trace amounts of acid and its reversibility with bases in non-aqueous solvents. Further, a dip-stick experiment was also carried out for the detection of acid-base vapor in a wide range of concentrations. Furthermore, the overlapping indicator method is explored to estimate acid dissociation constants in the non-aqueous medium. Moreover, we have constructed the INHIBIT (INH) and IMPLICATION (IMP) molecular logic gates exploring the reversibility of HDBD due to the cascade introduction of acid-base as chemical encoded inputs. Utilizing a reversible and reproducible detecting method, we have constructed a molecular-scale additional memory device that demonstrates binary logic “Writing-Reading-Erasing-Reading” and “Multi-write” functions. This finding provides a new way for designing acid-base indicators, which could estimate the acid dissociation constants of various acids in the non-aqueous environment which is fundamentally important in the field of acid-catalyzed organic synthesis.

Biomass-derived sensor for selective detection of Fe(III) ions in non-aqueous environments

Eco-friendly biomass-derived nanocarbons have gained considerable attention for detecting metallic pollutants, such as iron, in the environment. In addition, fluorescence probes are in high demand due to the growing need for iron detection in various organic solvents. Herein, we synthesize luminescent biomass-derived carbon nanoparticles (BMCNPs) from Kalanchoe pinnata plant leaves using a simple single-step solvothermal method. The synthesized BMCNPs emit red fluorescence in non-aqueous environments (organic solvents) and exhibit excellent fluorescence stability and solubility in both aqueous and non-aqueous media. The quenching of fluorescence emissions from BMCNPs in non-aqueous medium, facilitated by the addition of Fe(III) ions, demonstrates the ability of BMCNPs to serve as probes for detecting trace quantities of iron impurities. Experimental results confirm that the fluorescence from the BMCNPs is influenced by a ligand-to-metal charge transfer-assisted dynamic quenching mechanism. The proposed sensor is suitable for the real-time detection of iron in organic solvents, where iron contamination occurs due to the corrosion of iron metal. The fluorescence quantum yield of the probe is determined to be ∼11 %. The detection limit for Fe(III) in N,N-dimethylformamide using the synthesized probe is determined to be 1.9 µM. This study provides a platform for detecting Fe(III) ions in non-aqueous media. The proposed probe overcomes the limitation of Fe(III) ion-specific aqueous solubility, enabling the detection of Fe(III) ions in non-aqueous media due to the solubility and red emission specificity of BMCNPs in non-aqueous environments.

Bio-Inspired histidine-based copper complex: An efficient and robust electrocatalyst for electrochemical hydrogen evolution

The quest for an efficient and sustainable electrocatalyst for hydrogen evolution reaction (HER) using earth-abundant elements is crucial for cost-effective and environmentally friendly hydrogen production. While many catalysts show good activity and stability in strongly basic conditions, fewer materials are effective under neutral conditions, which are more practical for electrolyzer operations. This study introduces a dinuclear copper catalyst, [Cu2(μ-OH) (μ-NO3) (L)2], where L is the Schiff base ligand derived from salicylaldehyde and histidine amino acid (Complex 1), for HER in both aqueous and non-aqueous environments. In non-aqueous conditions, with acetic acid as a proton source, the catalyst exhibits outstanding HER performance, achieving an overpotential of 170 mV. At an acid concentration of 0.086 M, it achieves a catalytic current of ∼17.5 mA cm−2 at an overpotential of 0.52 V. Remarkably, in fully aqueous neutral conditions, Complex 1 reaches a significant current density with an ic/ip ratio of ∼82 at a scan rate of 1.0 V s−1, and an apparent rate constant (kobs) for electrocatalytic HER of ∼13,200 s−1. The catalyst also shows excellent activity in 0.1 M H3PO4, with low overpotentials of ∼150 mV at 2.0 mA cm⁻2 and 270 mV at 10.0 mA cm⁻2. In controlled potential electrolysis (CPE), the catalyst maintains stable catalytic currents of 25 mA cm⁻2 and 75 mA cm⁻2 for 18–28 h at a potential of 0.590 V vs. RHE in neutral and acidic conditions, respectively, without noticeable decrease in catalytic current. Detailed characterizations confirm the molecular integrity of the catalyst and its predominantly homogeneous catalytic mechanism.

Designed 2D protein crystals as dynamic molecular gatekeepers for a solid-state device

The sensitivity and responsiveness of living cells to environmental changes are enabled by dynamic protein structures, inspiring efforts to construct artificial supramolecular protein assemblies. However, despite their sophisticated structures, designed protein assemblies have yet to be incorporated into macroscale devices for real-life applications. We report a 2D crystalline protein assembly of C98/E57/E66L-rhamnulose-1-phosphate aldolase (CEERhuA) that selectively blocks or passes molecular species when exposed to a chemical trigger. CEERhuA crystals are engineered via cobalt(II) coordination bonds to undergo a coherent conformational change from a closed state (pore dimensions <1 nm) to an ajar state (pore dimensions ~4 nm) when exposed to an HCN(g) trigger. When layered onto a mesoporous silicon (pSi) photonic crystal optical sensor configured to detect HCN(g), the 2D CEERhuA crystal layer effectively blocks interferents that would otherwise result in a false positive signal. The 2D CEERhuA crystal layer opens in selective response to low-ppm levels of HCN(g), allowing analyte penetration into the pSi sensor layer for detection. These findings illustrate that designed protein assemblies can function as dynamic components of solid-state devices in non-aqueous environments.

Modulating water hydrogen bonding within a non-aqueous environment controls its reactivity in electrochemical transformations

Modulating water hydrogen bonding within a non-aqueous environment controls its reactivity in electrochemical transformations

A Turn-Off Fluorescent Sensor for Metal Ions Quantifies Corrosion in an Organic Solvent

We demonstrate that the corrosion of AISI 1045 medium carbon steel and pure aluminum can be quantified by the turn-off fluorescent sensor Phen Green-SK (PGSK) in ethanol-based solutions. We first evaluate the dependence of the chelation enhanced quenching of PGSK on iron and aluminum ion concentrations. Subsequently, we apply PGSK to examine the anodic dissolution of metal corrosion. The observed time-dependent PGSK-quenching quantifies the corrosion rates of two metals over 24 h of immersion in ethanol-based solutions. The PGSK-based quantification of corrosion is compared to scanning electron microscopy and electrochemical techniques, including open circuit potential and Tafel extrapolation. The corrosion rates calculated from PGSK-quenching and Tafel extrapolation are in agreement, and both indicate a decrease in corrosion rates over 24 h. Our work shows PGSK can efficiently sense and quantify anodic corrosion reactions at metal interfaces, especially in organic solvents or other non-aqueous environments where the application of electrochemical techniques can be limited by the poor conductivity of the surrounding medium.

Proton Diffusion in Liquid 1,2,3-Triazole Studied by Incoherent Quasi-Elastic Neutron Scattering.

Improving the proton transport in polymer electrolytes impacts the performance of next-generation solid-state batteries. However, little is known about proton conductivity in nonaqueous systems due to the lack of an appropriate level of fundamental understanding. Here, we studied the proton transport in small molecules with dynamic hydrogen bonding, 1,2,3-triazole, as a model system of proton hopping in a nonaqueous environment using incoherent quasi-elastic neutron scattering. By using the jump-diffusion model, we identified the elementary jump-diffusion motion of protons at a much shorter length scale than those by nuclear magnetic resonance and impedance spectroscopy for the estimated long-range diffusion. In addition, a spatially restricted diffusive motion was observed, indicating that proton motion in 1,2,3-triazole is complex with various local correlated dynamics. These correlated dynamics will be important in elucidating the nature of the proton dynamics in nonaqueous systems.

Photothermal Conversion of the Oleophilic PVDF/Ti3C2Tx Porous Foam Enables Non-Aqueous Liquid System Applicable Actuator.

Various physical and chemical reaction processes occur in non-aqueous liquid systems, particularly in oil phase systems. Therefore, achieving efficient, accurate, controllable, and cost-effective movement and transfer of substances in the oil phase is crucial. Liquid-phase photothermal actuators (LPAs) are commonly used for material transport in liquid-phase systems due to their remote operability and precise control. However, existing LPAs typically rely on materials like hydrogels and flexible polymers, commonly unsuitable for non-aqueous liquids. Herein, a 3D porous poly(vinylidene fluoride)(PVDF)/Ti3C2Tx actuator is developed using a solvent displacement method. It demonstrates directional movement and controlled material transport in non-aqueous liquid systems. When subject to infrared light irradiation (2.0Wcm-2), the actuator achieves motion velocities of 7.3 and 6mms-1 vertically and horizontally, respectively. The actuator's controllable motion capability is primarily attributed to the foam's oil-wettable properties, 3D porous oil transport network, and the excellent photothermal conversion performance of Ti3C2Tx, facilitating thermal diffusion and the Marangoni effect. Apart from multidimensional directions, the actuator enables material delivery and obstacle avoidance by transporting and releasing target objects to a predetermined position. Hence, the developed controllable actuator offers a viable solution for effective motion control and material handling in non-aqueous liquid environments.

Titration vs. GC-MS Analysis to Determine the Factors Affecting the Esterification Activity of Candida rugosa Lipase Immobilized onto Celite

The activity of lipases to catalyze the synthesis of esters in a non-aqueous environment can be assessed by performing a simple esterification study. In such tests, titration of the remaining acid has been one of the most used methods to determine the reaction progress due to its simplicity. Nonetheless, the execution of the titration is not always as simple as it sounds. In this study, Candida rugosa lipase is immobilized onto celite matrix, and its esterification activity was evaluated by catalyzing the reaction between butanol and butyric acid. Among the factors affecting the esterification activity of the immobilized enzymes are celite:CRL ratio, buffer pH during immobilization, and post-immobilization drying time. The titration results were analyzed using factorial design, ANOVA test, and Pareto chart. Here, the ambiguity of the titration results is showcased. On the other hand, analyzing the esterification results using GC-MS allowed optimization of the immobilization method to be performed. Finally, factors affecting the activity of the immobilized enzyme can be better assessed when the esterification results were analyzed using GC-MS.

Duplex-forming oligocarbamates with tunable nonbonding sites.

In biopolymers such as proteins and nucleic acids, monomer sequence encodes for highly specific intra- and intermolecular interactions that direct self-assembly into complex architectures with high fidelity. This remarkable structural control translates into precise control over the properties of the biopolymer. Polymer scientists have sought to achieve similarly precise control over the structure and function of synthetic assemblies. A common strategy for achieving this goal has been to exploit existing biopolymers, known to associate with specific geometries and stoichiometries, for the assembly of synthetic building blocks. However, such systems are neither scalable nor amenable to the relatively harsh conditions required by various materials science applications, particularly those involving non-aqueous environments. To overcome these limitations, we have synthesized sequence-defined oligocarbamates (SeDOCs) that assemble into duplexes through complementary hydrogen bonds between thymine (T) and diaminotriazine (D) pendant groups. The SeDOC platform makes it simple to incorporate non-hydrogen-bonding sites into an oligomer's array of recognition motifs, thereby enabling an investigation into this unexplored handle for controlling the hybridization of complementary ligands. We successfully synthesized monovalent, divalent, and trivalent SeDOCs and characterized their self-assembly via diffusion ordered spectroscopy, 1H-NMR titration, and isothermal titration calorimetry. Our findings reveal that the binding strength of monovalent oligomers with complementary pendant groups is entropically driven and independent of monomer sequence. The results further show that the hybridization of multivalent oligomers is cooperative, that their binding enthalpy (ΔH) and entropy (TΔS) depend on monomer sequence, and that sequence-dependent changes in ΔH and TΔS occur in tandem to minimize the overall change in binding free energy.

Electrochemical Intercalation and Exfoliation of CrSBr into Ferromagnetic Fibers and Nanoribbons.

Recent studies dedicated to layered van der Waals crystals have attracted significant attention to magnetic atomically thin crystals offering unprecedented opportunities for applications in innovative magnetoelectric, magneto-optic, and spintronic devices. The active search for original platforms for the low-dimensional magnetism study has emphasized the entirely new magnetic properties oftwo dimensional (2D) semiconductor CrSBr. Herein, for the first time, the electrochemical exfoliation of bulk CrSBr in a non-aqueous environment is demonstrated. Notably, crystal cleavage governed by the structural anisotropy occurred along two directions forming atomically thin and few-layered nanoribbons. The exfoliated material possesses an orthorhombic crystalline structure and strong optical anisotropy, showing the polarization dependencies of Raman signals. The antiferromagnetism exhibited by multilayered CrSBr gives precedence to ferromagnetic ordering in the revealed CrSBr nanostructures. Furthermore, the potential application of CrSBr nanoribbons is pioneered for electrochemical photodetector fabrication and demonstrates its responsivity up to 30µAcm-2 in the visible spectrum. Moreover, the CrSBr-based anode for lithium-ion batteries exhibited high performance and self-improving abilities. This anticipates that the results will pave the way toward the future study of CrSBr and practical applications in magneto- and optoelectronics.

Interlayer Confined Water Enabled Pseudocapacitive Sodium-Ion Storage in Nonaqueous Electrolyte.

Electrochemical capacitors have faced the limitations of low energy density for decades, owing to the low capacity of electric double-layer capacitance (EDLC)-type positive electrodes. In this work, we reveal the functions of interlayer confined water in iron vanadate (FeV3O8.7·nH2O) for sodium-ion storage in nonaqueous electrolyte. Using an electrochemical quartz crystal microbalance, in situ Raman, and ex situ X-ray diffraction and X-ray photoelectron spectroscopy, we demonstrate that both nonfaradaic (surficial EDLC) and faradaic (pseudocapacitance-dominated Na+ intercalation) processes are involved in the charge storages. The interlayer confined water is able to accelerate the fast Na+ intercalations and is highly stable (without the removal of water or co-intercalation of [Na-diglyme]+) in the nonaqueous environment. Furthermore, coupling the pseudocapacitive FeV3O8.7·nH2O with EDLC-type activated carbon (FeVO-AC) as the positive electrode brings comprehensive enhancements, displaying the enlarged compaction density of ∼2 times, specific capacity of ∼1.5 times, and volumetric capacity of ∼3 times compared to the AC electrode. Furthermore, the as-assembled hybrid sodium-ion capacitor, consisting of an FeVO-AC positive electrode and a mesocarbon microbeads negative electrode, shows a high energy density of 108 Wh kg-1 at 108 W kg-1 and 15.3 Wh kg-1 at 8.3 kW kg-1. Our results offer an emerging route for improving both specific and volumetric energy densities of electrochemical capacitors.

Electrostatic interactions of enzymes in non-aqueous conditions: insights from molecular dynamics simulations

Electrostatic interactions of enzymes and their effects on enzyme activity and stability are poorly understood in non-aqueous conditions. Here, we investigate the contribution of the electrostatic interactions on the stability and activity of enzymes in the non-aqueous environment using molecular dynamics simulations. Lipase was selected as active and lysozyme as inactive model enzymes in non-aqueous media. Hexane was used as a common non-aqueous solvent model. In agreement with the previous experiments, simulations show that lysozyme has more structural instabilities than lipase in hexane. The number of hydrogen bonds and salt bridges of both enzymes is dramatically increased in hexane. In contrast to the other opinions, we show that the increase of the electrostatic interactions in non-aqueous media is not so favorable for enzymatic function and stability. In this condition, the newly formed hydrogen bonds and salt bridges can partially denature the local structure of the enzymes. For lysozyme, the changes in electrostatic interactions occur in all domains including the active site cleft, which leads to enzyme inactivation and destabilization. Interestingly, most of the changes in electrostatic interactions of lipase occur far from the active site regions. Therefore, the active site entrance regions remain functional in hexane. The results of this study reveal how the changes in electrostatic interactions can affect enzyme stability and activity in non-aqueous conditions. Moreover, we show for the first time how some enzymes, such as lipase, remain active in a non-aqueous environment. Communicated by Ramaswamy H. Sarma

Adsorption modeling for contaminant removal in plastic dissolution recycling: Investigating an amino ketone-based red dye

The widespread inclusion of additives in plastics has posed a significant challenge to increasing global plastic recycling rates. This study explores the potential of adsorption in non-aqueous environment as a novel approach for plastic waste dissolution recycling. Activated charcoal was selected as the adsorbent for the removal of Solvent Red 135, a commonly used amino ketone-based dye, from polystyrene (PS) solutions. Three solvents, namely o-xylene, limonene, and butyl acetate, were investigated. Adsorption experiments were conducted at 293 K, and the results were analyzed using both classical and statistical physics models. The activated charcoal exhibited the highest single component adsorption capacity for the dye when butyl acetate was used as the solvent, while it showed negligible adsorption for PS in all three solvents. When dealing with mixtures of the dye and 1.0 wt% PS in butyl acetate, a removal efficiency of 99% was achieved at an adsorbent dose of 2.0 g L-1. However, when the PS concentration in the solvent increased to 10 wt%, the required adsorbent dose rose to 3.3 g L-1. Modeling results indicated that monolayer adsorption occurred via a multi-molecular adsorption mechanism, with an approximate adsorbed dye molecule count of 1.5 per adsorption site. The adsorption energy for all three solvents ranged between 0 and 40 kJ mol-1, indicating that the adsorption process is predominantly driven by physical forces and is an endothermic process. This study presents a foundational assessment of adsorption as an effective solvent-based technique for the removal of additives in plastic recycling.

Nonaqueous Ion Pairing Exemplifies the Case for Including Electronic Polarization in Molecular Dynamics Simulations.

The inclusion of electronic polarization is of crucial importance in molecular simulations of systems containing charged moieties. When neglected, as often done in force field simulations, charge-charge interactions in solution may become severely overestimated, leading to unrealistically strong bindings of ions to biomolecules. The electronic continuum correction introduces electronic polarization in a mean-field way via scaling of charges by the reciprocal of the square root of the high-frequency dielectric constant of the solvent environment. Here, we use ab initio molecular dynamics simulations to quantify the effect of electronic polarization on pairs of like-charged ions in a model nonaqueous environment where electronic polarization is the only dielectric response. Our findings confirm the conceptual validity of this approach, underlining its applicability to complex aqueous biomolecular systems. Simultaneously, the results presented here justify the potential employment of weaker charge scaling factors in force field development.

Enhanced phase transfer of Ag-nanospheres using amine-containing amphiphiles for sensitive chemical detection in nonaqueous environments

Effective phase transfer of Ag-nanospheres (AgNSs) was achieved through molecular interactions, rendering them interfacially compatible with various organic chemicals. This transfer was confirmed by distinct color changes and scanning electron microscope images, and the transferred AgNSs were employed as substrates for surface-enhanced Raman spectroscopy (SERS), enabling the sensitive detection of rhodamine 6G molecules dispersed in nonaqueous solutions. Notably, this detection capability extended to concentrations as low as 1 × 10−14 M. These findings underscore the potential of phase transferred AgNSs as versatile SERS substrates for sensitive chemical sensing in nonaqueous environments.

Electrochemistry of Selected Acetaminophen Derivatives

Acetaminophen (N-(4-hydroxyphenyl)acetamide, APAP) belongs to the most frequently used pharmaceuticals with analgesic and antipyretic effect [1]. The metabolization of APAP via oxidation pathway lead to formation of highly reactive intermediate N-acetyl-p-benzoquinone imine (NAPQI). It immediately reacts with a nucleophile e.g. with glutathione by formation of respective conjugate. The level of such conjugates can be directly linked to the toxicity of APAP in humans.Hence, three derivatives of acetaminophen were synthesized and characterized [2]. In this contribution, we focus on the characterization of redox properties of selected acetaminophen derivatives (see scheme 1) which were studied by means of cyclic voltammetry, rotating-disk voltammetry and UV-VIS absorption spectrometry. The oxidation mechanism was studied in phosphate buffers of different pH as well as in non-aqueous environment of N,N-dimethylformamide The influence of substituents on the electron transfer mechanism was estimated and corresponding rate constants were evaluated. We found that the protonation/deprotonation of acetaminophen derivatives act as a rate determining steps in aqueous media. The obtained electrochemical results were accompanied by chemical ones using reaction of the conjugates with diphenylpicrylhydrazyl (DPPH radical assay) in order to examine their interaction with radical, hence radical scavenging ability. Acknowledgement This work was supported by the Czech Science Foundation (GA19-11867S). References L. O. Boreus, F. Sandberg, Acta physiologica Scandinavica 1953, 28, 261-265.J. Vanova, D. Malinak, R. Andrys, M. Kubat, T. Mikysek, E. Rousarova, K. Musilek, T. Rousar, P. Cesla, J. Chromatogr. A 2022, 1669, 11. Figure 1