Search Results (129)

Icariin (ICA) is widely recognized for its health benefits. In this work, we examined the intermolecular interactions between ICA and proteinase K (PK) via multi-spectroscopic techniques and molecular simulations. The experimental findings revealed that ICA quenched the fluorescence emission of PK by forming a noncovalent complex. Both hydrogen bonding and van der Waals interactions are essential for the complex’s formation. Then Förster resonance energy transfer (FRET), competitive experiments, and synchronous fluorescence spectroscopy were adopted to verify the formation of the complex. Molecular docking studies demonstrated that ICA could spontaneously bind to PK by hydrogen bonding and hydrophobic interactions, which is consistent with the spectroscopic results. The PK-ICA complex’s dynamic stability was evaluated using a 50 ns molecular dynamics (MD) simulation. The simulation results revealed no significant structural deformation or positional changes throughout the entire simulation period. The complex appears to be rather stable, as seen by the average root-mean-square deviation (RMSD) fluctuations for the host protein in the PK-ICA complex of 1.08 Å and 3.09 Å. These outcomes of molecular simulations suggest that ICA interacts spontaneously and tightly with PK, consistent with the spectroscopic findings. The approach employed in this research presents a pragmatic and advantageous method for examining protein–ligand interactions, as evidenced by the concordance between empirical and theoretical findings. Full article

In order to explore the essence of the anticoccidiosis of anticoccidial drugs under bioelectric currents, the intermolecular double-proton transfer and conformational transformation of 4-pyridone-3-carboxylic acid were investigated by quantum chemistry calculations (at the M06-2X/6-311++G**, M06-2X/aug-cc-pVTZ and CCSD(T)/aug-cc-pVTZ levels) and finite temperature string (FTS) under external electric fields. The solvent effect of H₂O on the double-proton transfer was evaluated by the integral equation formalism polarized continuum model. The results indicate that the influences of the external electric fields along the direction of the dipole moment on double-proton transfer are significant. The corresponding products are controlled by the direction of the external electric field. Due to the first-order Stark effect, some good linear relationships form between the changes of the structures, atoms in molecules (AIMs) results, surface electrostatic potentials, barriers of the transition state, and the external electric field strengths. From the gas to solvent phase, the barrier heights increased. The spatial order parameters (ϕ, ψ) of the conformational transformation could be quickly converged through the umbrella sampling and parameter averaging, and thus the free-energy landscape for the conformational transformation was obtained. Under the external electric field, there is competition between the double-proton transfer and conformational transformation. The external electric field greatly affects the cooperativity transfer, while it has little effect on the conformational transformation. This study is helpful in the selection and updating of anticoccidial drugs. Full article

This article discloses the synthesis of four new positional isomeric zwitterionic ligands exhibiting semi-flexible and flexible characteristics—n-pyridinium-1,2,3-triazole-4-carboxy-5-Acetate (n-PTCA), and n-methylpyridinium-1,2,3-triazole-4-carboxy-5-Acetate (n-MPTCA; where n = 3, 4)—which were derived from an aqueous solution of the corresponding sodium salts in an acidic medium (HCl). These compounds are successfully synthesized and characterized with FT-IR and multinuclear NMR spectroscopy; likewise, proper single crystals are obtained for each compound. All compounds adopt zwitterionic forms in the solid state, which are stabilized via intermolecular proton transfer processes involving HCl and solvent molecules. A single-crystal X-ray analysis revealed how positional isomerism and molecular flexibility influence the supramolecular topology. Specifically, 3-PTCA and 4-PTCA exhibit isomorphic hydrogen bond networks, while 3-MPTCA and 4-MPTCA display distinct packing motifs, attributed to the presence of a methylene spacer between the pyridinium and triazole rings. The Hirshfeld surface analysis quantitatively confirmed the dominance of O···H/H···O and N···H/H···N interactions in the solid-state architecture. These strong hydrogen-bonding networks are indicative of the potential proton-conductive behavior in the crystalline state, positioning these compounds as promising candidates for applications in proton-conducting materials. The structural insights gained underscore the pivotal role of molecular topology in tailoring crystal packing, with implications for the rational design of zwitterionic ligands in functional materials, including MOFs and coordination polymers. The calculated HOMO-LUMO energy gaps reveal a significant electronic variability among the ligands, influenced primarily by the positional isomerism and structural flexibility introduced by the methylene spacer. Full article

Laccases are versatile enzymes capable of oxidizing a wide variety of antibiotics. In this study, the mechanism of catalytic oxidation of first-generation tetracyclines, namely, oxytetracycline, tetracycline, and chlortetracycline, by the Melanocarpus albomyces laccase enzyme was investigated using molecular docking and DFT calculations. Molecular docking studies revealed that all three substrates exhibit negative interaction energies, indicating stable enzyme–substrate complexes, with tetracycline and chlortetracycline showing the highest binding affinities. Global reactivity indices obtained by DFT confirmed the high electrophilicity of the enzyme active site, particularly the aminoacidic residues Glu235 and His508, favoring electron transfer from the substrates. In addition, NBO analysis allowed quantification of the energy of hydrogen bonds in enzyme–substrate interactions, evidencing their key role in the stabilization of the complex. Proton transfer analysis suggested two possible mechanisms: (1) a direct concerted transfer and (2) a process mediated by water molecules. The results provide insights into the thermodynamics, electronic structure, and nature of intermolecular interactions governing the oxidation of tetracyclines by the enzyme, highlighting their potential in bioremediation strategies for antibiotic degradation. Full article

In this work, Mg²⁺ modified chitosan (Mg²⁺/CS) is proposed and successfully designed. By investigating the effects of the Mg²⁺ and CS interaction on hydrogen bonding, dipoles, charge density, surface potential, and roughness, the coordination between Mg²⁺ and CS is verified and the mechanism of coordination improving tribological properties is elucidated. The Mg²⁺/CS coordination structure enhances intermolecular interactions, promoting the formation of new hydrogen bonds and increasing the dipoles. Compared to CS, the relative dielectric constant of Mg²⁺/CS increased by 76%, the surface potential increased by 70 mV, and the root mean square roughness increased by 39.4 nm. The open-circuit voltage, short-circuit current, and charge density of the triboelectric nanogenerator (TENG) fabricated from Mg²⁺/CS were increased by 100%, 94%, and 75%, respectively, compared to the CS-TENG fabricated from pure CS. The coordination of Mg²⁺ increased the charge density of the Mg²⁺/CS-TENG, significantly enhancing its charge transfer capability. The Mg²⁺/CS-TENG successfully provided power for photodetectors and LEDs. Mg²⁺/CS exhibited excellent flexibility and skin adhesion, and the Mg²⁺/CS-TENG successfully converted the mechanical energy generated by human joint motion into electrical signals. The coordination structure of Mg²⁺ with CS enhances the triboelectric performance of Mg²⁺/CS-TENG, providing new light for the research of chitosan-based TENGs. Full article

A hybrid material composed of IRMOF-3 and ZnO (IRMOF-3/ZnO) was synthesized to enhance photocatalytic methylene blue (MB) degradation under visible-light irradiation. Scanning electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, and diffuse-reflectance UV-Vis analyses confirmed the successful integration of ZnO into the IRMOF-3 framework. Compared with unmodified IRMOF-3, the hybrid demonstrated superior MB decomposition, as evidenced by faster reaction rate constants and shorter half-lives. Monitoring the MB absorbance at 670 nm (λ_max) revealed more pronounced colorant removal when IRMOF-3/ZnO was exposed to a visible-light source. Diffuse-reflectance UV-Vis spectroscopy showed that IRMOF-3 has a band gap of 2.7 eV, whereas IRMOF-3/ZnO exhibits a slightly higher band gap of 2.8 eV. This modest shift, coupled with the strong interaction between the ZnO semiconductor and the MOF’s amine functionalities, enabled two distinct energy-transfer pathways: intermolecular transfer from IRMOF-3 linkers (acting as visible-light antennas) to ZnO, and intramolecular transfer from Zn to IRMOF-3. Together, these pathways generated abundant free radicals for efficient dye degradation. Despite the necessity for careful synthesis protocols and control of operating conditions to preserve the MOF structure and optimize ZnO loading, the IRMOF-3/ZnO hybrid shows promise as a robust, cost-effective photocatalyst for water-pollutant remediation, taking advantage of the more abundant visible region of solar light. Full article

III-nitrides are crucial materials for solar flow batteries due to their versatile properties. In contrast to the well-studied MOVPE reaction mechanism for AlN and GaN, few works report gas-phase mechanistic studies on the growth of InN. To better understand the reaction thermodynamics, this work revisited the gas-phase reactions involved in metal–organic vapor-phase epitaxy (abbreviated as MOVPE) growth of InN. Utilizing the M06-2X function in conjunction with Pople’s triple-ζ split-valence basis set with polarization functions, this work recharacterized all stationary points reported in previous literature and compared the differences between the structures and reaction energies. For the reaction pathways which do not include a transition state, rigorous constrained geometry optimizations were utilized to scan the PES connecting the reactants and products in adduct formation and XMIn (M, D, T) pyrolysis, confirming that there are no TSs in these pathways, which is in agreement with the previous findings. A comprehensive bonding analysis indicates that in TMIn:NH₃, the In-N demonstrates strong coordinate bond characteristics, whereas in DMIn:NH₃ and MMIn:NH₃, the interactions between the Lewis acid and base fragments lean toward electrostatic attraction. Additionally, the NBO computations show that the H radical can facilitate the migration of electrons that are originally distributed between the In-C bonds in XMIn. Based on this finding, novel reaction pathways were also investigated. When the H radical approaches MMInNH₂, MMIn:NH₃ rather than MMInHNH₂ will generate and this is followed by the elimination of CH₄ via two parallel paths. Considering the abundance of H₂ in the environment, this work also examines the reactions between H₂ and XMIn. The Mulliken charge distributions indicated that intermolecular electron transfer mainly occurs between the In atom and N atom whiling forming (DMInNH₂)₂, whereas it predominately occurs between the In atom and the N atom intramolecularly when generating (DMInNH₂)₃. Full article

Phase transformations induced by short optical pulses are mainstream in studies on the dynamics of cooperative electronic states. We present a semiphenomenological modeling of spatiotemporal effects expected when optical excitons are intricate with the order parameter such as in, e.g., organic compounds with neutral-ionic ferroelectric phase transitions. A conceptual complication appears here, where both the excitation and the ground state ordering are built from the intermolecular electronic transfer. To describe both thermodynamic and dynamic effects on the same root, we adopt, for the phase transition, a view of the excitonic insulator—a hypothetical phase of a semiconductor that appears if the exciton energy becomes negative. After the initial pumping pulse, a quasi-condensate of excitons can appear as a macroscopic quantum state that then evolves, while interacting with other degrees of freedom which are prone to an instability. The self-trapping of excitons enhances their density, which can locally surpass a critical value to trigger the phase transformation. The system is stratified in domains that evolve through dynamical phase transitions and may persist even after the initiating excitons have recombined. Full article

The development of efficient dyes for photon harvesting in dye-sensitized solar cells (DSSCs) is a critical area of research with the potential to enhance renewable energy technologies. This manuscript presents a novel approach to engineering dye structures (abbreviated as D2 dye features, an anthanthrene core with a resonance energy of E_R = 694 kJ/mol and a reported power conversion efficiency (η) of 5.27%) by systematically replacing an anthanthrene core with various aromatic cores, aiming to understand the influence of resonance energy on molecular performance. By designing seven new dyes with resonance energies ranging from 255 to 529 kJ/mol, we conducted in-depth computational studies using Density Functional Theory (DFT) and Time-Dependent Density Functional Theory (TDDFT) to explore the effects of π-aromatic linkers on their electronic properties. Our findings reveal key insights into intermolecular charge-transfer (ICT) mechanisms and how they relate to the resonance energy of dye cores, highlighting the significance of balanced charge mobilities in optimizing optoelectronic characteristics, as shown by the D9 dye with a naphthacene core. Full article

Polyamorphic transitions driven by high-energy mechanical milling (nanomilling) are studied in thioarsenide As₄Se_n-type glassy alloys obtained by melt quenching deviated from arsenic triselenide As₂Se₃ stoichiometry towards tetraarsenic pentaselenide (g-As₄Se₅) and tetraarsenic tetraselenide (g-As₄Se₄). This employs a multiexperimental approach based on powder X-ray diffraction (XRD) analysis complemented by thermophysical heat transfer, micro-Raman scattering (micro-RS) spectroscopy, and revised positron annihilation lifetime (PAL) analysis. Microstructure scenarios of these nanomilling-driven transformations in arsenoselenides are identified by quantum-chemical modeling using the authorized modeling code CINCA (the Cation Interlinked Network Cluster Approach). A straightforward interpretation of a medium-range structure response of a nanomilling-driven polyamorphism in the arsenoselenides is developed within the modified microcrystalline model. Within this model, the diffuse peak-halos arrangement in the XRD patterning is treated as a superposition of the Bragg-diffraction contribution from inter-planar correlations supplemented by the Ehrenfest-diffraction contribution from inter-atomic (inter-molecular) correlations related to derivatives of network As₂Se₃-type and molecular As₄Se₄-type conformations. Changes in the medium-range structure of examined glassy arsenoselenides subjected to nanomilling occur as an interplay between disrupted intermediate-range ordering and enhanced extended-range ordering. The domination of network-forming conformations in arsenoselenides deviated from As₂Se₃ stoichiometry (such as g-As₄Se₅) results in rather slight changes in their calorimetric heat-transfer and micro-RS responses. At the atomic-deficient level probed by PAL spectroscopy, these changes are accompanied by reduced positron trapping rate of agglomerated multiatomic vacancies and vacancy-type clusters in an amorphous As-Se network. Under an increase in As content beyond the g-As₄Se₅ composition approaching g-As₄Se₄, nanomilling-driven polyamorphic transitions, which can be classified as reamorphization (amorphous I-to-amorphous II) phase transitions, are essentially enhanced due to the higher molecularity of these glassy alloys enriched in thioarsenide-type As₄Se₄ cage-like molecular entities and their low-order network-forming derivatives. Full article

Photo-thermo-electric conversion devices represent a promising technology for converting solar energy into electrical energy. Photothermal materials, as a critical component, play a significant role in efficient conversion from solar energy into thermal energy and subsequently electrical energy, thereby directly influencing the overall system’s efficiency in solar energy utilization. However, the application of single-component photothermal materials in photo-thermo-electric conversion systems remains limited. The exploration of novel photothermal materials with broad-spectrum absorption, a high photothermal conversion efficiency (PCE), and a robust output power density is highly desired. In this study, we investigated a black cuprous halide compound, [Cu₂Cl₂PA]_n (1, PA = phenazine), which exhibits broad-spectrum absorption extending into the near-infrared (NIR) region. Compound 1 demonstrated a high NIR-I PCE of 50% under irradiation with an 808 nm laser, attributed to the metal-to-ligand charge transfer (MLCT) from the Cu(I) to the PA ligands and the strong intermolecular π–π interactions among the PA ligands. Furthermore, the photo-thermo-electric conversion device constructed using compound 1 achieved a notable output voltage of 261 mV and an output power density of 0.92 W/m² under the 1 Sun (1000 W/m²) xenon lamp. Full article

The main purpose of this study is to characterize the nature of the low-energy singlet excited states of the anthranilic acid homodimer (AA₂) and their changes (symmetry breaking) caused by deformation of the centrosymmetric, ground state structure of AA₂ towards the geometry of the S₁ state. We employ both the correlated ab initio methods (approximate Coupled Clusters Singles and Doubles—CC2 and CASSCF/NEVPT2) as well as the DFT/TDDFT calculations with two exchange–correlation functionals, i.e., B3LYP and CAM-B3LYP. The composition of the wavefunctions is investigated using the one-electron transition density matrix and difference density maps. We demonstrate that in the case of AA₂, small asymmetric distortions of geometry bring about unproportionally large changes in the excited state wavefunctions. We further provide comprehensive characterization of the AA₂ electronic structure, showing that the excitation is nearly completely localized on one of the monomers, which stands in agreement with the experimental evidence. The excitation increases the π-electronic coupling of the substituents and the aromatic ring, but only in the excited monomer, while the changes in the electronic structure of the unexcited monomer are negligible (after geometry relaxation). The increased electronic density strengthens both intra- and intermolecular hydrogen bonds formed by the carbonyl oxygen atom of the excited monomer, making them significantly stronger than in the ground state. Although the overall pattern of changes remains qualitatively consistent across all methods employed, CC2 predicts more pronounced excitation-induced modifications of the electronic structure compared to the more routinely used TDDFT approach. The most important deficiency of the B3LYP functional in the present context is locating two charge-transfer states at erroneously low energies, in close proximity of the S₁ and S₂ states. The range-corrected CAM-B3LYP exchange–correlation functional gives a considerably improved description of the CT states at the price of overshot excitation energies. Full article

In order to reduce the massive heat duty of amine-based CO₂ capture technology, an AlOOH/FeOOH composite catalyst (AF-M/N) was synthesized to speed up the CO₂ desorption rates and reduce the heat duty of an aqueous MEA solution. The catalysis of AF-M/M from 1/9 to 9/1 was investigated comprehensively, with characterization of the catalytic desorption with heat duty and desorption factors. Results indicated the special composite catalyst (AF-1/9) possessed optimized catalysis with a relative heat duty of 78.7% and a desorption factor of 0.0037 × 10⁻³ (mol CO₂/L² kJ min) and relative desorption factor of 194.7%. The structure–activity correlations indicated that the mesopore surface area (MSA), which reached 329 m²/g, and Brϕnsted/Lewis acid ratio (B/L ratio) of 0.11 were the most important factors for enhancing catalysis. Furthermore, molecular simulations were conducted for the catalytic carbamate breakdown mechanism, focusing on the “isomerization” of “carbamate acid” vs. “Zwitterion” as the key step. From the DFT study, the isomerization was most likely to proceed with H₂O as catalyst via intermolecular proton transfer instead of intramolecular proton transfer, with an activation energy Ea of 85.9 kJ/mol. With the aid of AlOOH the isomerization was further facilitated due to stabilized Zwitterion, and the Ea decreased to 69.2 kJ/mol. The results not only synthesized a new heterogeneous catalyst but also revealed the map of “isomerization” on a molecular level. Such a discovery indicates that water-assisted proton transfer is advantageous for catalytic carbamate breakdown. Full article

Ratiometric fluorescent sensing based on dual-emitting fluorescent coordination polymers (FL-CPs) has attracted intense attention due to their sensing accuracy and easy visualization when compared with sensing relying solely on monochromatic FL-CPs. In this work, a series of rare-earth metal-based CPs, formuled as [(CH₃)₂NH₂][Ln(bpdc)₂] (Ln³⁺ = Y³⁺, Eu³⁺ and Tb³⁺, H₂bpdc = biphenyl-4,4′-dicarboxylic acid), are presented, which show dual emission aroused from the Ln³⁺ ions and the inefficient intermolecular energy transfer from ligands to Ln³⁺ metals. For clarity, the as-made Ln-CPs are named Eu-bpdc, Tb-bpdc, and Y-bpdc based on the corresponding Ln³⁺. Notably, Eu-bpdc, presented as an example, could be used as FL sensing material ratiometric to Fe³⁺ ions. The ratio of FL intensity of Eu³⁺ ions to bpdc²⁻ ligands (I₄₁₅/I₆₁₅) showed a good linear relationship with the concentrations of Fe³⁺ ions. Moreover, the detection process could be visibly monitored through a change from purple to blue when Eu-bpdc was used as an FL proble. This work provides a good example for exploring visibly ratiometric sensors based on FL-CPs. Full article

A novel (E)-1-(4-methylbenzylidene)-4-(3-isopropylphenyl) thiosemicarbazone was synthesized in a one-pot four-step synthetic route. Fourier transform infrared spectroscopy (FTIR), ¹H and ¹³C nuclear magnetic resonances (NMR), single-crystal X-ray diffraction, and UV-visible absorption spectroscopy were utilized to confirm the successful preparation of the title compound. Single-crystal data indicated that the intramolecular hydrogen bond N(3)-H(3)···N(1) and intermolecular hydrogen bond N(2)-H(2)···S(1) (1 − x, 1 − y, 1 − z) existed in the crystal structure and packing of the title compound. Besides the covalent interaction, the non-covalent weak intramolecular hydrogen bond N(3)-H(3)···N(1) discussed by atoms in molecules (AIM) theory also functioned in maintaining the title compound’s crystal structure. The strong intermolecular hydrogen bond N(2)-H(2)···S(1) (1 − x, 1 − y, 1 − z) discussed by Hirshfeld surface analysis played a major role in maintaining the title compound’s crystal packing. The local maximum and minimum electrostatic potential of the title compound was predicted by electrostatic potential (ESP) analysis. The UV-visible spectra and HOMO-LUMO analysis revealed that the title compound has a low ΔE_HOMO–LUMO energy gap (3.86 eV), which implied its high chemical reactivity due to the easy occurrence of charge transfer interactions within the molecule. Molecular docking and in vitro antifungal assays evidenced that its antifungal activity is comparable to the reported pyrimethanil, indicating its usage as a potential candidate for future antifungal drugs. Full article