Strong H-bonds Research Articles

Synthesis and properties of metal trifluoride complexes with amide-functionalised tacn macrocycles and radiofluorination of [GaF3(L1)] by 18F/19F isotopic exchange.

Three amide-functionalised tacn macrocyclic derivatives (tacn = 1,4,7-triazacyclononane) are reported, two tris-amide derivatives, L1 containing three -CH2C(O)NHPh pendant arms, L2 containing three -CH2CH2C(O)NHiPr pendant arms, and one mono-amide, L3, containing iPr groups on two of the tacn amine functions and a single -CH2C(O)NHPh function on the third. The reactions of these new ligands towards [MF3(dmso)(OH2)2] (M = Al, Ga) and towards FeF3·3H2O in alcoholic solution afford the complexes [MF3(L)] (L = L1-L3) in good yields as powdered solids. These complexes are characterised by IR and multinuclear NMR spectroscopy (diamagnetic species only) and mass spectrometry. [GaF3(L1)], [GaF3(L3)] and [FeF3(L3)] are also characterised by single crystal X-ray analysis. The corresponding reactions involving [InF3(dmso)(OH2)2] yield mixtures of products (along with F-), consistent with the M-F bond strengths decreasing as group 13 is descended. A few crystals of the target complex, [InF3(L2)], were also obtained from one such reaction. All of the complexes adopt fac-octahedral coordination via the amine N-donor atoms and retain the three fluoride ligands both in solution and in the solid state. Extensive intramolecular hydrogen-bonding involving the amide NH pendant groups and the MF3 moieties is evident in the crystal structures. In the isostructural [MF3(L3)] (M = Ga, Fe) complexes the head-to-tail C(O)NH⋯F H-bonded dimers observed in the solid state resemble those found frequently in organic compounds and that form the cornerstone of many supramolecular assemblies. This is consistent with the MF3 fragments being strong H-bond acceptors. Radiofluorination of [GaF3(L1)] by 18F/19F isotopic exchange in MeOH at 3 μmol mL-1 precursor concentration and using aqueous [18F]F- in target water (75% : 25%) with gentle heating (80 °C, 10 min) gave ca. 20% radiochemical yield of [Ga18FF2(L1)]. In contrast, no 18F incorporation occurs with [GaF3(L3)] under any of the conditions explored.

Using a simple coating strategy to evolve polylactic acid into sand-fixation material with nutrient-rich reservoir by strong H-bonding interaction at phase interface

Developing simple and eco-friendly methods for polylactic acid (PLA) modification and establishing strong interfacial interactions between phases are still worthwhile research topics. Only by enabling sand barriers to continuously provide water and fertilizer for sand-fixing plants can effective control of desertification be truly achieved. Herein, a simple and eco-friendly coating functionalmodification strategy for PLA was introduced, involving in-situ curing of urea-aldehyde (UF)/polyacrylic acid (PAA) prepolymer after coating on PLA and then continuous rolling. During the preparation process, –NH in the amide group and –OH in the carboxyl group of UF/PAA form strong intermolecular H-bonding with C = O of PLA, resulting in high interfacial bonding strength and significant improvement in mechanical and hydrophilic properties of the modified PLA mesh. Wind erosion resistance, water absorption and holding capacity, nutrient content, and plant growth of the treated sand all display a very positive response. Effective surface coating modification evolves PLA into a “nutrient-rich reservoir” for sand-fixing plants without affecting its performances, thus truly achieving the desired but never achieved effective combination of natural sand fixation and mechanical sand barrier fixation, exhibiting great significance for further improving application performances and expanding applying fields of PLA through surface functional modification that is easy to industrialize.

Highly efficient adsorption of ciprofloxacin from aqueous solutions by waste cation exchange resin-based activated carbons: Performance, mechanism, and theoretical calculation

This study focused on the preparation of a highly efficient activated carbon adsorbent from waste cation exchange resins through one-step carbonization to remove ciprofloxacin (CIP) from aqueous solutions. Scanning electron microscopy, X-ray diffraction, Fourier-transform infrared spectrometry, and X-ray photoelectron spectroscopy were used to characterize the physicochemical properties of the carbonized materials. The CIP removal efficiency, influencing factors, and adsorption mechanisms of CIP on the carbonized resins were investigated. Density functional theory (DFT) computations were performed to elucidate the adsorption mechanisms. The CIP removal reached 93 % when the adsorbent dosage was 300 mg/L at 25 °C. The adsorption capacity of the carbonized resins to CIP gradually decreased with an increasing pH from 3.0 to 7.0 and sharply declined with a pH from 7.0 to 11.0. The adsorption process better fitted by the pseudo second-order kinetic and Langmuir models, indicating that the interaction between CIP and the carbonized resins was monolayer adsorption. The maximum adsorption capacity fitted by the Langmuir model was 384.4 mg/g at 25 °C. Microstructural analysis showed that the adsorption of CIP on the carbonized resins was a joint effect of H-bonding, ion exchange, and graphite-N adsorption. Computational results signified the strong H-bonding and ion exchange interactions existed between CIP and carbonized resins. The high adsorption and reusability suggest that waste cation exchange resin-based activated carbons can be used as an effective and reusable adsorbent for removing CIP from aqueous solutions.

Role of Exchange Cations and Layer Charge on the Dynamics of Confined Water.

Describing the dynamic behavior of water confined in clay minerals is a fascinating challenge and crucial in many research areas, ranging from materials science and geotechnical engineering to environmental sustainability. Water is the most abundant resource on Earth, and the high reactivity of naturally occurring hydrous clay minerals used since prehistoric times for a variety of applications means that water-clay interaction is a ubiquitous phenomenon in nature. We have attempted to experimentally distinguish the rotational dynamics and translational diffusion of two distinct populations of interlayer water, confined and ultraconfined, in the sodium (Na) forms of two smectite clay minerals, montmorillonite (Mt) and hectorite (Ht). Samples hydrated at a pseudo one-layer hydration (1LH) state under ambient conditions were studied with quasi-elastic neutron scattering (QENS) between 150 and 300 K. Using a simplified revised jump-diffusion and rotation-diffusion model (srJRM), we observed that while interlayer water near the ditrigonal cavity in Ht forms strong H-bonds to both adjacent surface O and structural OH, H-bonding of other more prevalent interlayer water with the surface O is weaker compared to Mt, inducing a higher temperature for dynamical changes of confined water. Given the lower layer charge and faster dynamics observed for Ht compared to Mt, we consider this strong evidence confirming the influence of the interlayer cation and surfaces on confined water dynamics.

Strong H-bonding from Zeolite Bro̷nsted Acid Site to Water: Origin of the Broad IR Doublet.

Hydrogen bonding between water molecules and zeolite Bro̷nsted acid sites (BAS) has received much attention due to the significant influence of water on the adsorption and catalytic properties of these widely used porous materials. When a single water molecule is adsorbed at the BAS, the zeolite O-H stretch vibration decreases in frequency and splits into two extraordinarily broad bands peaked near 2500 and 2900 cm-1 in the infrared (IR) spectrum. This broad doublet feature is the predominant IR signature used to identify and interpret water-BAS H-bonding at low hydration levels, but the origin of the band splitting is not well understood. In this study, we used broadband two-dimensional infrared (2D IR) spectroscopy to investigate zeolite HZSM-5 prepared with a single water molecule per BAS. We find that the 2D IR spectrum is not explained by the most common interpretation of Fermi resonance coupling between the stretch and the bend of the BAS OH group, which predicts intense excited-state transitions that are absent from the experimental results. We present an alternative model of a double-well proton stretch potential, where the band splitting is caused by excited-state tunneling through the proton-transfer barrier. This one-dimensional model reproduces the basic experimental pattern of transition frequencies and amplitudes, suggesting that the doublet bands may originate from a highly anharmonic potential in which the excited state proton wave functions are delocalized over the H-bond between zeolite BAS and adsorbed H2O. Additional details about molecular orientation and coordination of the adsorbed water molecule are also resolved in the 2D IR spectroscopy.

Molecular structure, spectroscopy, molecular docking, and molecular dynamic studies of tetrahydroneoprzewaquinone as potent cervical cancer agent

Abstract Cervical cancer is one of the most prevalent cancer-related diseases, causing accelerated morbidity and mortality rates in low-income countries and African states. This study explores the potential of (3R,3′R)-2,2′,3,3′-tetrahydroneoprzewaquinone (TDN) as a treatment for cervical cancer by investigating its structural and molecular properties using molecular modelling technique, which include; DFT, molecular docking, molecular dynamic simulation. The results are promising, with TDN demonstrating exceptional stability in the energy gap (E g) as well as through natural bond order analysis (NBO). π → σ* electronic transitions were found to contribute mainly to the molecule’s stability, with an outstanding total stabilization energy (E (2)). Docking exercises showed that TDN binds more favorably to the pro-apoptotic receptor 4s0o with a stronger H-bond compared to the conventional DOX drug, which interacted less effectively with TDN and more strongly with the anti-apoptotic protein, forming an outstanding strong H-bond. Molecular dynamics simulations also revealed that TDNʼs interaction with the pro-apoptotic protein (TDN_4S0o) was more stable than the standard DOX drug (DOX_4s0o). The H-bond plot indicated that TDN could effectively interact with both anti and pro-apoptotic receptors, forming approximately 1 to 4 hydrogen bonds between TDN_1g5M with respect to each picosecond (ps) ranging from 0 to 1000 ps. In contrast, the number of hydrogen bonds fluctuated when DOX interacted with the anti-apoptotic protein (1g5M), ranging from 1 to 5 H-bonds. Overall, these results suggest that TDN may be a promising drug candidate for cervical cancer treatment.

TD-DFT analysis of the photo-ring-opening reaction of the flav-3-en-2-ol in acetonitrile solution: Functional choice and effect of solvated hydrogen bond

Of the forty hybrid functionals supported by Gaussian 16, only fourteen functionals with small contributions from the exact Hartree-Fock exchange demonstrated the breaking of the C2-O1 bond of flav-3-en-2-ol: TPSSh, O3LYP, τHCTHhyb, B3LYP, B3P86, B3PW91, B971, B972, X3LYP, B98, APF, APFD, mPW1LYP, and mPW3PBE. TPSSh and O3LYP gave rise to a cis-2-hydroxychalcone transition accompanied by ground-state intramolecular proton transfer (GSIPT), and the remaining twelve functionals selected showed a return to the flav-3-en-2-ol with the recovery of the C2-O1 bond. The strong H-bond of acetonitrile with flav-3-en-2-ol has a striking effect on the consequences of the excitation in comparison with a single flav-3-en-2-ol molecule: optimization of the S1 excited state of the solvated complex leads to the breaking of the C2-O1 bond by O3LYP functional only. However, upon relaxation of the excited enol form, this bond was recovered, and a return to the flav-3-en-2-ol occurred. Nevertheless, the O3LYP functional gives a theoretical model consistent with the experiment: the H-bond of flav-3-en-2-ol with the acetonitrile molecule is a switch in the reaction path. If this H-bond is present at the excitation moment, then the flav-3-en-2-ol molecule undergoes a C2-O1 bond cleavage but recovers upon relaxation. If this H-bond is absent, then the flav-3-en-2-ol molecule transforms into the enol form which goes further into cis-2-hydroxychalcone. The excitation of the solvated complex causes a pronounced strengthening of this intermolecular H-bond. GSIPT is caused by a change in the polarization of the enol form during its electronic relaxation, as a result of which the proton begins to experience a stronger attraction to the opposite part of the molecule.

CNS-Active p38α MAPK Inhibitors for the Management of Neuroinflammatory Diseases: Medicinal Chemical Properties and Therapeutic Capabilities.

During the last two decades, many p38α mitogen-activated protein kinase (p38α MAPK) inhibitors have been developed and tested in preclinical/clinical studies for the treatment of various disorders, especially problems with the origin of inflammation. Previous studies strongly suggest the involvement of the p38α MAPK pathway in the pathogenesis of neurodegenerative disorders. Despite the significant progress made in this field, so far no studies have focused on p38α MAPK inhibitors that have the capability to be used for the treatment of neurodegenerative disorders. In the present review, we evaluated a wide range of well-known p38α MAPK inhibitors (more than 140 small molecules) by measuring key physicochemical parameters to identify those capable of successfully crossing the blood-brain barrier (BBB). As a result, we identify about 50 naturally occurring and synthetic p38α MAPK inhibitors with high potential to cross the BBB, which can be further explored in the future for the treatment of neurodegenerative disorders. In addition, a detailed analysis of the previously released X-ray crystal structure of the inhibitors in the active site of the p38α MAPK enzyme revealed that some residues such as Met109 play a critical role in the occurrence of effective interactions by constructing strong H-bonds. This study can encourage scientists to focus more on the design, production, and biological evaluation of new central nervous system (CNS)-active p38α MAPK inhibitors in the future.

Active carbon monoliths from soft brown coal: A systematic study of their preparation, pore structure modification and characterization

High surface area active carbons in a ‘honeycomb monolith’ (HM) configuration can be prepared directly from soft brown coal by a novel approach. Kneading the coal into a plasticine consistency enables it to be extruded in HM form, then dried, carbonized and activated, retaining its structural integrity throughout these steps. Unlike higher rank coals, soft brown coal, which inherently contains relatively high oxygen functional group concentrations and high moisture contents, develops a strong H-bonding network during kneading. This opens the way to a novel and simpler method of preparing activated carbons in a monolith configuration. A systematic study was therefore conducted to evaluate the potential of these monoliths for being converted into higher value activated carbons by a low-cost process. Carbon honeycomb monoliths HMs from brown coal were modified by carbon dioxide (CO2) activation with a uniform domain size over a wider range of activation conditions (1–3 h, 750–950 °C) and the products were characterized by N2 adsorption (surface area and porosity), SEM, TEM, Raman spectroscopy, XPS and elemental analysis. The optimum conditions for development of porosity, aromaticity and a graphitizing structure were activation at 900 °C for 3 h. Interestingly, higher temperatures did not yield additional benefits. These materials should be useful in applications requiring highly ordered carbon.

Exploring the Substrate-Assisted Dehydration of Chorismate Catalyzed by Dehydratase MqnA from QM/MM Calculations: The Role of Pocket Residues and the Hydrolysis Mechanism of N17D Mutant.

MqnA is the first enzyme on the futalosine pathway to menaquinone, which catalyzes the dehydration of chorismate to yield 3-enolpyruvyl-benzoate (3-EPB). MqnA is also the only chorismate dehydratase known so far. In this work, based on the recently determined crystal structures, we constructed the enzyme-substrate complex models and conducted quantum mechanics/molecular mechanics (QM/MM) calculations to elucidate the reaction details of MqnA and the critical roles of pocket residues. The calculation results confirm that the MqnA-catalyzed dehydration of chorismate follows the substrate-assisted E1cb mechanism, in which the enol carboxylate in the side chain of the substrate is responsible for deprotonating the C3 of chorismate. This proton transfer process is much slower than C4-OH departure. Calculations on different mutants reveal that S86 and N17 are important for anchoring the enol carboxylate of the substrate in a favorable conformation to extract the C3-proton. The strong H-bonds formed between the enol carboxylate of chorismate and S86/N17 play a key role in stabilizing the reaction intermediate. Consistent with the experimental observations, our calculations demonstrate that the MqnA N17D mutant also shows hydrolase activity and the typical enzyme-catalyzed hydrolysis mechanism is elucidated. The protonated D17 is responsible for saturating the methylene group of chorismate to start the hydrolysis reaction. The orientation of the carboxyl group of D17 is key in determining MqnA to be a dehydratase or hydrolase.

Fluoro-2,6-dimethylphenyl mono-hydroxychlorin and porphyrin congeners

Mono-hydroxychlorins are uncommon macrocycles that have only been synthetically realized by modifying porphyrin rings using the harsh oxidizing agent OsO4. We show here that a more directed delivery of the mono-hydroxychlorin may be concomitantly obtained from the oxidation of porphyrinogen using the mild conditions of the high dilution Lindsey porphyrin forming reaction where water content is minimized by using dry CHCl3 within the environment of a glovebox. We now report the direct synthesis of 17,18-dihydro-18-hydroxy-5,10,15,20-tetrakis-(4-fluoro,2,6-dimethylphenyl)-porphyrin (2H-TFChl-[Formula: see text]OH) together with the corresponding freebase porphyrin TFP. The TFP has been metalated with FeBr2 and MgBr2•OEt2 resulting in metalloporphyrins Fe(III)TFP(Cl) and Mg(II)-TFP which have been structurally characterized by single-crystal X-ray crystallography. We find that the excited state properties of the mono-hydroxychlorin are similar to that of its parent TFP and Mg(II)TFP porphyrin congeners. Excited state deactivation by vibronic coupling to the high energy O-H oscillator is circumvented with the hydroxyl group remote to the 18[Formula: see text]-electron framework of the chlorin ring. These results reveal that strong H-bonding groups may be introduced on the periphery of the chlorin ring while maintaining the light-gathering properties that lie at the heart of photosynthesis of the chlorin ring.

3D Tea-Residue Microcrystalline Cellulose Aerogel with Aligned Channels for Solar-Driven Interfacial Evaporation Co-generation.

Solar-driven interfacial evaporation co-generation (SIE-CG) technology is of great significance in solving the problem of water and energy shortage. Herein, we report the ionic liquid-assisted alignment of waste biomass tea residue-based microcrystalline cellulose for aerogels (abbreviated as TPPA-5) with aligned channels for solar-driven interfacial evaporation co-generation. In the ionic liquid, strong H-bonding is formed between the pyranoid rings of cellulose combined with the slow freezing technique, resulting in the microcrystalline cellulose being reoriented, which allowed TPPA-5 to form abundant aligned channels after solvent replacement and freeze-drying. These aligned channels enable the brine to form a localized circulating flow, which is conducive to the improvement of the TPPA's evaporation rate and salt resistance. The salinity gradient is naturally formed in the channel of TPPA, which enables TPPA-5 to show excellent power generation performance. The evaporation rate of TPPA-5 can reach 3.39 kg m-2 h-1 under 1 kW m-2. With methanol as a highly polar proton solvent, the maximum output voltage obtained was 67.534 mV due to the overlapping electric double-layer effect formed by hydrogen protons on the TPPA surface, and the energy utilization efficiency is 95.95%. Moreover, TPPA-5 can purify pesticide-containing wastewater, which has the advantages of being recyclable and environmentally friendly, showing potential application value in the field of seawater desalination and steam co-generation.

Investigating Intramolecular H Atom Transfer Dynamics in β-Diketones with Ultrafast Infrared Spectroscopies and Theoretical Modeling.

The vibrational signatures and ultrafast dynamics of the intramolecular H-bond in a series of β-diketones are investigated with 2D IR spectroscopy and computational modeling. The chosen β-diketones exhibit a range of H atom donor-acceptor distances and asymmetry along the H atom transfer coordinate that tunes the intramolecular H-bond strength. The species with the strongest H-bonds are calculated to have very soft H atom potentials, resulting in highly red-shifted OH stretch fundamental frequencies and dislocation of the H atom upon vibrational excitation. These soft potentials lead to significant coupling to the other normal mode coordinates and give rise to the very broad vibrational signatures observed experimentally. The 2D IR spectra in both the OH and OD stretch regions of the light and deuterated isotopologues reveal broadened and long-lived ground-state bleach signatures of the vibrationally hot molecules. Polarization-sensitive transient absorption measurements in the OH and OD stretch regions reveal notable isotopic differences in orientational dynamics. Orientational relaxation was measured to occur on ∼600 fs and ∼2 ps time scales for the light and deuterated isotopologues, respectively. The orientational dynamics are interpreted in terms of activated H/D atom transfer events driven by collective intramolecular structural rearrangements.

Molecular Dynamics Simulation Study of the Selective Inhibition of Coagulation Factor IXa over Factor Xa.

Thromboembolic disorders, arising from abnormal coagulation, pose a significant risk to human life in the modern world. The FDA has recently approved several anticoagulant drugs targeting factor Xa (FXa) to manage these disorders. However, these drugs have potential side effects, leading to bleeding complications in patients. To mitigate these risks, coagulation factor IXa (FIXa) has emerged as a promising target due to its selective regulation of the intrinsic pathway. Due to the high structural and functional similarities of these coagulation factors and their inhibitor binding modes, designing a selective inhibitor specifically targeting FIXa remains a challenging task. The dynamic behavior of protein-ligand interactions and their impact on selectivity were analyzed using molecular dynamics simulation, considering the availability of potent and selective compounds for both coagulation factors and the co-crystal structures of protein-ligand complexes. Throughout the simulations, we examined ligand movements in the binding site, as well as the contact frequencies and interaction fingerprints, to gain insights into selectivity. Interaction fingerprint (IFP) analysis clearly highlights the crucial role of strong H-bond formation between the ligand and D189 and A190 in the S1 subsite for FIXa selectivity, consistent with our previous study. This dynamic analysis also reveals additional FIXa-specific interactions. Additionally, the absence of polar interactions contributes to the selectivity for FXa, as observed from the dynamic profile of interactions. A contact frequency analysis of the protein-ligand complexes provides further confirmation of the selectivity criteria for FIXa and FXa, as well as criteria for binding and activity. Moreover, a ligand movement analysis reveals key interaction dynamics that highlight the tighter binding of selective ligands to the proteins compared to non-selective and inactive ligands.

Single-Photon Ionization Induced New Covalent Bond Formation in Acrylonitrile(AN)-Pyrrole(Py) Clusters.

The formation of nitrogen-containing organic compounds is crucial for understanding chemical evolution and the origin of life in the interstellar medium (ISM). In this study, we explore whether acrylonitrile (AN) and pyrrole (Py) can form new nitrogen-containing compounds after single-photon ionization in their gaseous clusters by vacuum ultraviolet (VUV)-infrared (IR) spectroscopy and theoretical calculations. The results show that a strong linear H-bond is formed in neutral AN-Py, while cyclic or bicyclic H-bonded networks are formed in the neutral AN-Py2 cluster. It is found that the structure containing a new C-C covalent bond between two moieties in (AN-Py)+ is formed besides the formation of H-bonded structures after AN-Py is ionized by VUV light. In (AN-Py2)+ cluster cations, new C-C or C-N covalent bonds tend to be formed between two Py, with (Py)2+ as the core in the cluster. The results reveal that new covalent bonds are more likely to be formed between two Py species when AN and Py are present in the cationic clusters. These results provide spectroscopic evidence of the formation of new nitrogen-containing organic compounds from AN and Py induced by VUV, which are helpful for our understanding of the formation of diverse prebiotic molecules in interstellar space.

Preparation of UV-cured polyurethane-urea acrylate coatings with high hardness and toughness

Polyurethane-urea acrylate (PUUA) has been used to develop mechanically robust materials, due to the urea-based bifurcated H-bond. However, the uncontrollable reaction rate between diamine and diisocyanate makes it difficult to prepare PUUA. Herein, we put forward a simple method to synthesize PUUA, which was then used to prepare UV-cured PUUA coatings with simultaneous high hardness and excellent toughness. In our strategy, a novel diol containing urea group has been designed, which was employed as chain extender to synthesize PUUA at a controllable polymerization rate. By adopting chain extenders with different molecular structures, two kinds of PUUA were synthesized. The molecular structures of diol containing urea group and PUUA were identified by Fourier transform infrared spectroscopy (FTIR) and Nuclear magnetic resonance spectroscopy (1H NMR). Benefiting from the strong urea-based H-bond, the UV-cured PUUA films showed simultaneously enhanced mechanical strength and toughness. Specially, the optimal PUUA film exhibited high mechanical strength (19 MPa), high elongation at break (310 %), and high toughness (26.9 MJ m−3), which was 9.5, 2.8 and 19.2-fold increase compared with polyurethane acrylate (PUA) film without urea groups. Correspondingly, the UV-cured PUUA coatings exhibited higher impact resistance and higher hardness than PUA coating. This work provides a new avenue to develop PUUA for high-performance UV-curable coatings.

The effect of water molecules on paraquat salts: from physicochemical properties to environmental impact in the Brazilian Cerrado.

Introduction: The green revolution model that is followed in the Brazilian Cerrado is dependent on mechanization, chemical fertilization for soil dressing and correction, and the use of herbicides. Paraquat is a methyl viologen herbicide marketed as bipyridylium dichloride salts and used (in low doses) to combat weeds in their post-emergence stage. It is a non-selective pesticide that causes the peroxidation of the lipids that make up the cell membrane, and when it comes into contact with foliage, it results in the death of the plant. Methods: The effect of water molecules co-crystallized in Paraquat salt structures was analyzed in anhydrous, dihydrate, and trihydrate forms to understand those physicochemical properties in its redox activity. The frontier molecular orbitals were also carried out using DFT to obtain the chemical reactivity of the bipyridylium cation. Finally, the supramolecular arrangements were evaluated to analyze the physicochemical stability and acquire insights on superoxide anions. Results and discussion: The electronic structure indicated that the BP cation presents an acidic character due to its low ELUMO value, while the salt has a more basic character due to its high EHOMO value. For this reason, the BP ion is more susceptible to reduction during the weeds' photosynthesis process. During the process of plant photosynthesis, PQ is reduced to form a stable radical cation. In the supramolecular arrangement, the presence of water molecules increases the number of strong H-bonds, while the weak/moderate H-bonds are stabilized. PQ's toxic effects are observed in wildlife, domesticated animals, human populations, and ecosystems. The influence of PQ on the terrestrial environment is limited because of the soil adsorption capacity associated with good agricultural practices. The current use of good agricultural practices in the Cerrado seems not to prevent the environmental impacts of herbicides like PQ because it aims for the expansion and profitability of large-scale farming based on input-intensive practices instead of sustainable agriculture processes.

Peculiarities of the Spatial and Electronic Structure of 2-Aryl-1,2,3-Triazol-5-Carboxylic Acids and Their Salts on the Basis of Spectral Studies and DFT Calculations.

The molecular structure and vibrational spectra of six 1,2,3-triazoles-containing molecules with possible anticancer activity were investigated. For two of them, the optimized geometry was determined in the monomer, cyclic dimer and stacking forms using the B3LYP, M06-2X and MP2 methods implemented in the GAUSSIAN-16 program package. The effect of the para-substitution on the aryl ring was evaluated based on changes in the molecular structure and atomic charge distribution of the triazole ring. An increment in the positive N4 charge was linearly related to a decrease in both the aryl ring and the carboxylic group rotation, with respect to the triazole ring, and by contrast, to an increment in the pyrrolidine ring rotation. Anionic formation had a larger effect on the triazole ring structure than the electronic nature of the different substituents on the aryl ring. Several relationships were obtained that could facilitate the selection of substituents on the triazole ring for their further synthesis. The observed IR and Raman bands in the solid state of two of these compounds were accurately assigned according to monomer and dimer form calculations, together with the polynomic scaling equation procedure (PSE). The large red-shift of the C=O stretching mode indicates that strong H-bonds in the dimer form appear in the solid state through this group.

Combined Experimental and Computational Study of V-Substituted Lindqvist Polyoxotungstate: Screening by Docking for Potential Antidiabetic Activity.

In the current work, a novel vanadotungstate compound, (C6H9N2)4[V2W4O19]·2H2O (1), is isolated by a simple stepwise synthesis method and characterized by a combined experimental and computational study. Molecular docking is conducted for the first time for this kind of substituted Lindqvist polyoxometalates to elucidate for potential antidiabetic activity. Hence, the modeling results revealed a significant docking score of the reported compound to bind to the active sites of α-glucosidase with the lowest binding energy of -5.7 kcal/mol, where the standard drug acarbose (ACB) had -4.6 kcal/mol binding energy. The stability of binding was enhanced by strong H-bonding, van der Waals, and electrostatic interactions occurring in the three-dimensional (3D) supramolecular network of polyanionic vanadotungstate subunits templated with organic moieties as shown by X-ray diffraction and Hirshfeld analyses. Furthermore, density functional theory (DFT) calculations supported with photophysical measurements are also discussed to predict the most chemical and biological reactivity. In this view, the complete description of electronic and biological features of (1) is enhanced by determination of the highest occupied molecular orbital (HOMO)/least unoccupied molecular orbital (LUMO) energy, electronic density, ionization potential, electron affinity, etc. These chemical descriptors, intermolecular interactions, docking score, and binding free energy estimation are essential in understanding the reactivity of this bioactive compound offering potential inhibition of the α-glucosidase enzyme.

Soil organic matter carbon chemistry signatures, hydrophobicity and humification index following land use change in temperate peat soils

Peatlands play a critical role in the global carbon cycle, storing large amounts of carbon because of a net imbalance between primary production and the microbial decomposition of the organic matter. Nevertheless, peatlands have historically been drained for energy sources (e.g. peat briquettes), forestry, or agriculture - practices that could affect the quality of the soil organic matter (SOM) composition, hydrophobicity and humification index. This study compared the effect of land use change on the quality and composition of peatland organic material in Co-Offaly, Ireland. Specifically, drained and grazing peat (grassland), drained and forest plantation peat (forest plantation), drained and industrial cutaway peat (cutaway bog) and an undrained actively accumulating bog (as a reference for natural peatland) were studied. Fourier-transform infrared spectroscopy (FTIR) was used to examine the organic matter quality, specifically the degree of decomposition (DDI), carbon chemistry signatures, hydrophobicity and humification index. The ratio of hydrophobic to hydrophilic group intensities was calculated as the SOM hydrophobicity. In general, there is greater variance in the carbon chemistry signature, such as aliphatic methyl and methylene, C=O stretching of amide groups, aromatic C=C, strong H-bond C=O of conjugated ketones and O–H deformation and C– O stretching of phenolics and secondary alcohols of the peat samples from industrial cutaway bog samples than in the grassland and forest plantation samples. The hydrophobicity and the aromaticity of the soil organic matter (SOM) are significantly impacted by land use changes, with a trend of order active bog > forest plantation > industrial cutaway bog > grassland. A comparison of the degree of decomposition index of the peat from active bog showed a more advanced state of peat degradation in grassland and industrial cutaway bog and, to a lesser extent, in forest plantation.