Development of the Colle-Salvetti correlation-energy formula into a functional of the electron density

An organic emitter with enhanced fluorescence modulation, high emission efficiency, multicolor tunability in solution and solid states, and dual-channel sensing for selective cyanide detection

For many industrial application, there arise a demand for multistate with multicolor emissive materials due to its substantial applications than fluorophore shows emission in single state. Therefore, in this work donor-acceptor-donor' (D-A-D') based three organic emitters (DSE1-DSE3) were synthesized. A substituted phenyl ring and cyano vinyl unit are used to manage molecular geometry and steric hindrance to reduce the gap between AIE and ACQ, resulting in an improved dual-state emission. Solid state emission maxima for all chemicals were red shifted compared to solution state. Additionally, quantum yields and excited state fluorescence lifetime were higher in the solid state. Because of their donor-acceptor pattern, all of the dyes show positive solvatochromism. As the solvent polarity increases, the emission maxima of DSE1-DSE3 redshift gradually. These emitter probe DSE1-DSE3 showed redshift in aggregation emission (ACRE) in water which is considered to be a poor solvent, this is supported by DLS and SEM analysis. Meanwhile, the compound DSE1-DSE3 can detect cyanide ion selectivity over other competing anions via the absorbance and fluorescence channels. Under the effect of electron accepting cyano groups, the vinyl C = C bond was easily reacted by nucleophilic CN- which disturb the conjugated bridge of the compounds and prevented the ICT process between the donor and acceptor. The addition of cyanide ions to the compounds DSE1-DSE3 resulted in a significant red shift in absorbance and a total quenching of fluorescence intensity. For real life application, the probe successfully detects cyanide ion in various water samples. Besides, the developed DSE3-encapsulated polysulfone (PSF) capsule kit effectively sense cyanide ion in water.

Enhancing CO2 reduction with formamide-Ni@TiO2 catalyst

Formamide condensation with Ni can generate the NC structure, widely recognized as an efficient catalyst for electrocatalytic CO2 reduction reaction (CO2RR). To improve the utilization efficiency of Ni atoms, we introduced metal oxides as substrates to modulate the growth of a formamide-Ni (FA-Ni) condensate. FA-Ni@TiO2 demonstrated 2.8 times higher partial CO current density and Ni turnover frequency than FA-Ni, which were also higher than those of other FA-Ni@metal oxides, including ZrO2, Al2O3, Fe2O3, and ZnO. The improved performance of CO2RR can be attributed to the Ni content exposed on FA-Ni@TiO2 being twice that of the raw FA-Ni condensate. The Fourier transform infrared results suggested that formamide was adsorbed on TiO2 via the -CHO group, exposing -NH2 for potential interaction with Ni. As a result, Ni atoms were predispersed on the TiO2 surface. By contrast, the dispersion of Ni atoms was not enhanced by other metal oxides, such as Al2O3, Fe2O3, and ZnO, owing to the robust acidity of their surface sites. These metal oxides adsorbed formamide via -NH2, leading to the absence of extra -NH2 available for binding to Ni atoms. This study provides new insights into the development of appropriate substrates for single-atom catalysts.

Theoretical insight into the antioxidant activity of Theasinensin A

Theasinensin A (TSA), a dimeric flavan-3-ol from fermented teas, exhibits potent antioxidant activity exceeding that of its monomeric precursor, epigallocatechin gallate (EGCG). This study integrates experimental and computational methods (Density Functional Theory) to elucidate TSA's antioxidant mechanisms. DPPH assays revealed that TSA exhibited an IC50 value 2.4-fold lower than that of EGCG, indicating its superior radical scavenging efficacy. Electrostatic potential, frontier molecular orbital, and Laplacian bond order analyses identified the O4' - H group on the B-ring as the primary reaction site, with TSA showing higher reactivity than EGCG. Reaction enthalpy calculations further revealed that TSA requires less energy for double hydrogen donation, underscoring its thermodynamic advantage. Additionally, spin density analysis demonstrated the increased stability of TSA's phenoxy radical, which may be stabilized by its robust intramolecular hydrogen bonding, π-π stacking, and CH-π interactions. These findings highlight the unique structural and electronic properties of TSA that contribute to its superior antioxidant efficacy.

Exploring the colorimetric sensing mechanism of metal porphyrin on the degree of roasting from the perspective of density functional theory

Aroma quality is a key indicator of the degree of roasting of large-leaf yellow tea (LYT). In this study, a colorimetric sensing array (CSA) composed of tetraphenylporphyrin (TPP) was designed for the rapid quantitative detection of key volatile organic compounds (VOCs) in LYT. First, the responses of the CSA system were compared under three environmental conditions. The response intensity of the TPPs to the VOCs was analysed using density functional theory (DFT). Finally, on the basis of the DFT calculations, a streamlined CSA sensor incorporating a least-squares support vector machine model was designed for the quantitative detection of 2-ethyl-3,5-dimethylpyridazine, 2,5-dimethylpyrazine, benzaldehyde, dihydro-2-methyl-3-furanone, linalool, and trans-β-ionone at levels ranging from 0.005 to 5 ppm. The predictive coefficients and relative predictive deviations of the quantitative model ranged from 0.82 to 0.93 and 1.75 to 2.65, respectively. This study provides a theoretical basis for the construction of CSA and a novel perspective on the monitoring of tea processing and quality.

Unveiling the impact of the fluorophore pyrrole, indole, furan, benzofuran, thiophene, benzothiophene, and pyrene attachments on the C7 atom of the isomorphic fluorescent thieno-guanine: A theoretical investigation

Thieno-guanine (thG) is a prominent emissive surrogate of natural guanine (G), which almost perfectly mimics G in nucleic duplexes. In this paper, to widen the utility of thG, the C7 attachment effects by aromatic pyrrole, indole, furan, benzofuran, thiophene, benzothiophene, and pyrene on the structural, electronic, and photophysical properties of thG were theoretically examined by using the density functional theory (DFT) and the time-dependent DFT (TD-DFT). Calculations were performed employing the hybrid B3LYP and the long-range corrected CAM-B3LYP density functionals in combination with the 6-311++G(d, p) basis set. Rigid scan calculations and optimizations were performed to obtain the most stable rotamers, and totally 14 bases (including thG) were studied. The hole-electron theory and the interfragment charge transfer (IFCT) method were applied to reveal the intrinsic characteristics of the low-lying electron excitation processes. In water solution, all the S1 states of the thG-derivatives are highly allowed ππ∗ states dominated by HOMO (L)→LUMO (L) with some charges (0.028-0.193 e) been transferred from the introduced groups to the thG-moiety. The introduced groups can tune the photophysics of thG resulting in improved fluorescent properties, including visible excitation and emission wavelengths, greater absorption and emission intensities (oscillator strengths), and larger Stokes shifts. In water solution, all substituents display fluorescence wavelength longer than 500 nm and the Stokes shifts are larger than 100 nm. Also examined are the effects of base pairing with cytosine (C), and it was revealed that the S1 states of all the studied base pairs (totally 14) are local excitations of the thG-derivatives. Both the S1 state excitation energies and the fluorescence wavelengths are red-shifted to some extent after base pair with C, with a concomitantly decrease of the corresponding oscillator strength.

Effect of metal ions in Baijiu on cluster formation of water, ethanol, acetic acid and ethyl acetate molecules: Molecular dynamics and density functional theory studies

Metal ions in Baijiu play an important role in the formation of liquor flavor, but their molecular mechanism has not been studied yet. In this study, molecular dynamics was used to calculate the radial distribution function (RDF), coordination number, and mean square displacement (MSD) of K+, Ca2+, and Fe2+ in water, ethanol, acetic acid, and ethyl acetate systems. Density functional theory was used to determine the binding energy, geometric configuration, and charge distribution of different clusters. The results of the MSD and RDF indicate that Ca2+ and Fe2+ are easily encapsulated by water or ethanol molecules in the system, resulting in weaker diffusion ability than K+. The interaction energy between K+, Ca2+, and Fe2+ and each molecule in the system increases sequentially, especially for Fe2+, which significantly changes the charge of molecules in the cluster. There are hydrogen bonds between molecules in clusters formed with K+ as the core, but there are no hydrogen bonds between molecules in clusters formed with Ca2+ and Fe2+ as the core. The cohesion of clusters formed with K+, Ca2+, and Fe2+ as the core increased in that order. The results of this study lay a theoretical foundation for understanding the molecular mechanism of metal ions in Baijiu.

Mechanism of cyclization-degradation of silazanes: A DFT study

The present calculations at the B3LYP/6-31G (d) level confirm that the cyclization-degradation of silazanes proceeds via two mechanisms: Si-N bond interchange and hydrogen abstraction. The energy barrier for hydrogen abstraction is approximately 20 kcal/mol lower than that of the Si-N bond interchange pathway. Substituent effects critically influence the thermal stability of silazanes. For the Si-N bond interchange mechanism, factors that enhance nucleophilic attack or reduce Si-N bond strength destabilize silazanes. This implies that substituents with the electron-donating inductive effects, electron-donating conjugation effects, or bulky steric profiles should be avoided to improve thermal stability. In contrast, hydrogen abstraction predominantly occurs at chain termini. To suppress this pathway, substituents with low basicity and weak reducing capacity are recommended as terminal blocking groups. Based on these findings, using phenyl groups as terminal substituents represents an economically viable and thermodynamically favorable strategy for enhancing silazane stability.

Virtual screening, in silico pharmacokinetic and toxicity profiling of colchicine-based inhibitors of estrogen receptor of breast cancer

The declining efficacies of existing drugs against estrogen receptor positive (ER+) breast cancer due to multidrug resistance, acute toxicities, and poor pharmacokinetic properties has necessitated the discovery of newer ones. In this study, colchicine analogues with proven in vitro activities against breast cancer cells were screened against estrogen receptor alpha (ERα) via molecular docking simulations to identify some promising drug candidates. The identified ligands were further subjected to MM/GBSA calculations to ascertain their solvation-dependent Gibb's free energy of binding (∆GB). Three most promising ligands (MPLs); 12, 16, and 21 with ∆GB values of - 40.37, - 40.31, and - 40.26 kcal/mol, respectively, were identified. When compared with tamoxifen (standard drug) whose ∆GB value is - 38.66 kcal/mol, the MPLs appear more potent. The kinetic stabilities of 12, 16, and 21 were confirmed by DFT (B3LYP/6-31G*) calculations and the time-dependent thermodynamic stabilities of their complexes with ERα were established by molecular dynamic simulations. In addition, the MPLs display positive pharmacokinetic and toxicity profiles and could be excellent sources of potent and non-toxic drug candidates against ER+ breast carcinoma.

Exploring tiopronin adsorption on pristine and Al/Ga-doped boron nitride nanoclusters: A DFT approach for enhanced drug delivery

Tiopronin is a thiol-based medication recognized for its antioxidant properties, which may offer therapeutic benefits for various medical conditions. At present, it is utilized for the treatment of cystinuria and rheumatoid arthritis. However, its limited bioavailability poses a significant challenge for broader applications, necessitating high systemic doses to achieve localized therapeutic effects. The incorporation of a drug delivery system could help overcome this issue by allowing for controlled and targeted release. Functionalized B12N12 fullerenes present a promising platform with substantial potential for biomedical applications, particularly in drug delivery. In this study, the effect of loading the tiopronin drug on the structural and electronic properties of pure B12N12, AlB11N12 and GaB11N12 fullerenes nano agent were evaluated using density functional theory in both gas and aqueous environments. The adsorption energy of tiopronin over the fullerenes has been studied through its nucleophilic sites (COOH, NH2, CO, and SH). Based on our analysis, the adsorption energies are about -1.69, -3.38 and -1.96 eV for the most stable complexes of B12N12, AlB11N12 and GaB11N12, respectively. Electronic analysis showed that the HOMO-LUMO gaps decrease upon drug adsorption, resulting in significant changes in molecular orbital levels and quantum molecular descriptors. Additionally, quantum theory of atoms in molecules (QTAIM) analysis, electron localization function (ELF), and reduced density gradient (RDG) plots were explored to investigate interaction properties.

Elucidating the modulatory effects of heteroatoms and substituent groups on ESIPT dynamics and optical properties in HBBX derivants

The benzo furan-extended 2-(2'-hydroxybenzofuranyl) benzazole derivants (HBBX) have attracted widespread attention for their excellent photophysical properties. Some subtle structural alterations have been proven to influence the spectral characteristics significantly. However, a comprehensive understanding of the influence of structural regulation is still lacking. Here, the effects of heteroatoms and substituent groups on the excited state intramolecular proton transfer (ESIPT) process and photophysical properties of HBBX derivants are investigated by the density functional theory/time-dependent density functional theory (DFT/TDDFT). Our simulation results show that heteroatoms and substituent groups significantly change the hydrogen bond strength of HBBX derivants. To the heteroatoms, the HBBX substituted by the N atom (HBBI) has the lowest ESIPT energy barrier in the first excited state, and the substitution of tBu group (HBBO-1) can cause the maximum energy barrier reduction to the substituent groups. Moreover, the absorption, emission spectra and hole-electron analysis are consistent with the experimental results, and the simulation results show that HBBI has the lowest degree of intramolecular charge transfer and highest fluorescence intensity in all HBBX derivants. Our work will provide the comprehensive insight into the effects of heteroatoms and substituent groups on ESIPT processes and photophysical properties for the design of fluorescent materials.

Robust zincophilic-hydrophobic protection layer induces preferential growth of (0 0 2) crystal plane towards ultra-stable Zn anode

The practical deployment of aqueous zinc-ion batteries (AZIBs) in large-scale energy storage applications is hampered by short cycle lifespans and limited zinc utilization due to uncontrollable dendrite growth and water-induced side reactions. Herein, we propose an environmentally friendly electrolyte additive, 2-acrylamido-2-methylpropanesulfonic acid (AMPS), which features dual zincophilic sites and a hydrophobic group, to enhance Zn stability. Theoretical calculations and experimental characterizations demonstrate that AMPS can firmly adsorb onto the Zn (0 0 2) plane through its dual zincophilic sites (SO3H and NHCO), while the CC hydrophobic group orients toward the electrolyte, ultimately forming a stable zincophilic/hydrophobic interface on the Zn electrode in situ. This unique structure not only inhibits water-induced side hydrogen evolution reactions but also induces preferential deposit propagation along the (0 0 2) crystal plane. Benefiting from this synergetic effect, the Zn//Cu asymmetric cell with AMPS electrolyte maintains an ultrahigh average coulombic efficiency of 99.8 % for over 2500 cycles at 2 mA cm-2, achieving 1 mAh cm-2. Furthermore, the Zn//MnO2 full cell shows a high-capacity retention of 67.7 % at 1.8 A g-1 after 1000 cycles, confirming the effectiveness of the AMPS additive in improving the cyclability and performance of AZIBs.

A novel dual-channel fluorescent probe for the detection of peroxynitrite anions and lipid droplets in epileptic disease

Peroxynitrite (ONOO-) and lipid droplets (LDs) are crucial substances essential for maintaining normal physiological functions in biological systems. They play pivotal roles as biomarkers in the initiation and progression of various diseases, such as epilepsy. Therefore, the simultaneous detection of ONOO- and LDs in epilepsy disorders is of great importance. Here, we discovered that the fluorescence probe composed of trifluoromesulfonate and fluorophore can not only be used as the recognition site of ONOO-, but also has the property of LDs targeting. Therefore, we reasonable designed and synthesized a dual-channel fluorescent probe CBT, capable of simultaneously monitoring ONOO- and LDs. CBT exhibited exceptional dual-response properties: firstly, upon specific reaction with ONOO-, the resulting product BHD emitted a robust red fluorescent signal in the near-infrared region (749 nm); secondly, CBT selectively targeted and labeled LDs, emitting green fluorescence at 482 nm for effective LDs tracking. The signals from these two detection channels did not overlap, which significantly enhanced the accuracy and reliability of detection. Based on these characteristics, CBT has been successfully utilized in real-time imaging of ONOO- and LDs in epilepsy models of cells induced by various drugs. Notably, in a pentylenetetrazole (PTZ)-induced chronic epileptic mice model, CBT exhibited excellent efficacy in ONOO- imaging, further confirming its considerable potential for practical applications. In summary, this study validated CBT as an efficient tool capable of simultaneous detection and differentiation of ONOO- and LDs, presenting a novel and promising strategy for the early diagnosis and treatment of diseases such as epilepsy.

Signature of electronically excited states in Raman spectra of azobenzene derivatives. Computational and experimental approaches

Raman spectroscopy can provide highly sensitive and detailed information about the structural fingerprint of molecules, enabling their identification. In this study, our aim is to understand the enhanced intensity observed in experimental Raman measurements. Five azobenzene derivatives were selected, each substituted with different functional groups, for both experimental and theoretical investigations. To reproduce the experimental trend, we employed various levels of theory using the QM-DFT approach. Theoretical results were compared to experimental data through both qualitative and quantitative analyses. A good correlation between theoretical and experimental results was achieved when considering electronic transitions to predict the theoretical Raman spectra and interpret the experimental data. Our theoretical results indicate that even dark (nπ*) transitions, which are forbidden and have an oscillator strength close to zero, can have a signature in the Raman spectra due to the resonance effect with incident energy. Additionally, the vibrational modes stimulated by the presence of ππ* bright states, being at the pre-resonance with the incident energy, was clearly separated from the vibrational frequencies of the dark states, which was evinced in the Raman fingerprint. Theoretical Raman spectra of azobenzene derivatives, substituted with push-pull moieties, revealed contributions from the charge transfer transitions (nπ*CT, ππ*CT) as well as back-donation of electron density, observed for the first time in an azobenzene derivative. Our protocol, proposing a quantitative and qualitative overlap between theoretical and experimental data, confirms the presence of combination modes between vibrational levels and electronically excited states.

Exploring vacancy defects in s-I clathrate hydrates

This study investigates the role of vacancy defects in s-I clathrate hydrate structures, particularly in the presence of ethylene oxide (EO) molecules, through first-principles calculations. The structural properties, formation energies, and guest-host interactions of these vacancy defects were examined in both periodic systems and finite-size clusters. Our findings demonstrate that EO molecules significantly stabilize vacancy defects via hydrogen bonding, especially when forming double hydrogen bonds with dangling hydrogens (d-Hs) arising from the molecular vacancy defect. The encapsulation of EO in defect-free cages and its interaction with dangling oxygens (d-Os) were also analyzed, highlighting the superior stabilizing effect of double hydrogen bonds. These results provide new insights into the behavior of vacancy defects in hydrate structures and the potential role of polar guest molecules in enhancing defect stability and facilitating hydrate formation processes.

Effect of ergosterol or cholesterol on the morphology and dynamics of the POPC/sphingomyelin bilayer

Phase segregation and domain formation in cell membranes and model lipid bilayers have become a relevant topic in the last decades due to their role in important cell functions such as signaling and molecule-membrane interactions. To date, the most accepted explanation for the formation of these domains in mammalian cells is that cholesterol-enriched sphingomyelin patches of membrane form because of the preferential interaction between them. However, detailed information on molecular interactions within cholesterol-containing bilayers and their comparison with other sterol-containing bilayers, such as those containing ergosterol, is needed to understand the role these molecules have. Recent experimental findings have shown sterol-dependent differences in the morphology of supported lipid bilayers, but the molecular basis for these differences remains unclear. This work provides a molecular explanation for these differences using atomistic Molecular Dynamics simulations of lipid bilayers composed of 1-palmitoyl-2-oleoyl-glycero-3-phosphocholine (POPC) and N-palmitoyl-D-erythro-sphingosylphosphorylcholine (PSM) with 20 mol% of cholesterol or ergosterol. Atomic force microscopy was used to validate the simulation. The simulation ran for 11 μs and revealed that both sterols affect the morphology of the membrane. Key findings include: ergosterol induces greater order in PSM domains compared to cholesterol, lipid diffusion constants are lower in ergosterol-containing membranes, sterol flip-flop rates are significantly reduced in ergosterol-containing membranes and ergosterol leads to greater PSM-sterol enrichment. These molecular-level differences provide insight into the experimentally observed variations in domain formation and membrane properties between cholesterol and ergosterol-containing bilayers. Our findings contribute to the understanding of sterol-specific effects on membrane organization and dynamics, with potential implications for cellular processes and drug interactions in different organisms. STATEMENT OF SIGNIFICANCE: This study advances our understanding of how different sterols influence membrane properties through molecular dynamics simulations of three-component lipid membranes. Specifically, we investigate the effects of two major sterols: ergosterol, predominantly found in plants and fungi, and cholesterol, characteristic of mammalian cells. While extensive research has elucidated cholesterol's impact on lipid bilayers, studies on ergosterol's effects are comparatively limited. Our work provides a comprehensive comparison of these sterols, highlighting their similarities and differences. These insights not only enhance our knowledge of cell membrane structure and function, but also contribute to our understanding of selective drug permeability across membranes. This research has potential implications for both fundamental cell biology and pharmaceutical applications.

Photophysical and structural aspects of poly-L-tryptophan: π-π stacking interaction with an excited state intermolecular proton transfer probe 3-Hydroxynaphthoic acid revealed by experiments and molecular simulation

In biophysical studies involving proteins, the involvement of the intrinsic fluorophore Tryptophan and its energy transfer/binding interactions are already well-investigated areas. Theoretical studies have also been well corroborated with experimental findings. However, in polymeric Tryptophans (specifically homopolymers), several queries still need to be addressed - their structure, the environment of each Tryptophan and the binding preferences of the latter. This necessitated some detailed investigations on the poly-L-Tryptophan system both from experimental and theoretical standpoints. In this work, we have carried out both steady-state and time-resolved fluorescence studies along with low-temperature phosphorescence (LTP) of poly-L-tryptophan, and the nature of the emitting Tryptophan (Trp) residue in the latter has been characterized based on a comparison with the emission features of the parent monomer. The very large red-shift of the (0-0) band of phosphorescence in poly-L-Tryptophan has been explained through triplet-triplet energy transfer along with the structure of the latter which has been developed by theoretical modelling. The nature of the environment of the emitting Trp residue in poly-L-Trp has been compared with several multi-Tryptophan proteins where different Trp residues exhibit optically resolved (0-0) bands. The interaction of the excited state proton transfer (ESIPT) probe 3-hydroxynaphthoic acid (3-HNA) with poly-L-Trp has also been investigated in detail using fluorescence, LTP, and classical molecular dynamics simulations.

Catalytic ozonation of sulfamethoxazole using loaded CuOx/MgO-SiO2 silica aerogel catalyst: Performance, mechanisms and toxicity

Catalytic ozonation technology can quickly and inexpensively treat antibiotic wastewater, where the performance of catalysts determines the level of catalytic efficiency. In this study, CuOx/MgO-SiO2 (represented by CuMgSiO) catalysts were prepared using hydrothermal method. Their structure and properties were analyzed by X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS) and automatic specific surface area analyzer. The effects of O3 concentration, catalyst dosage and initial pH on the degradation of Sulfamethoxazole (SMX) were investigated. Catalytic ozonation mechanisms and degradation pathways of the pollutants were revealed by quenching experiments and liquid chromatography-mass spectrometry analysis. The toxicity of SMX and its intermediates was analyzed by ECOSAR software. The results showed that CuOx/MgO was successfully loaded onto SiO2 aerogel and the catalyst exhibited a porous network structure. The highest removal efficiency of SMX reached 87.92% and Kobs was 0.07045 min-1 under the optimum conditions, which was 35.9% and 2.77 times higher than those of ozonation alone. The ·OH, ·O2- and 1O2 were active species for the degradation of SMX, and 1O2 played a dominant role. Valence cycling between Cu2+/Cu+ and Mg2+/Mg and adsorption of O3 by surface hydroxyl groups were key steps in catalytic ozonation, and the toxicity of wastewater after treatment was greatly reduced. This study not only provides an economically feasible catalyst, but also offers a new perspective in the field of antibiotic wastewater treatment.

DFT and machine learning integration to predict efficiency of modified metal-free dyes in DSSCs

Power conversion efficiency (PCE) prediction in dye-sensitized solar cells (DSSCs) increasingly relies on computation and machine learning, lowering experimental demands and accelerating materials discovery. In this work we incorporated quantum-chemical descriptors, computed via density-functional theory (DFT), with cheminformatic descriptors generated using the Mordred library to train two machine learning models. The Random Forest and XGBoost models were trained on a dataset of 40 dyes, together with their literature experimental PCEs. The model stabilities were investigated using multiple random state configurations (30, 38, 42 and 50). The trained models were used to evaluate newly engineered dyes, and then validated through electronic structure analysis. The novel dyes are derivatives of: (E)-10-methyl-9-(3-(10-methylacridin-9(10H)-ylidene)prop-1-en-1-yl)acridin-10-ium (C-PE3), 10-methyl-9-((1E,3E)-5-(10-methylacridin-9(10H)-ylidene)penta-1,3-dien-1-yl)acridin-10-ium (C-PE5) and 10-methyl-9-((1E,3E,5E)-7-(10-methylacridin-9(10H)-ylidene)hepta-1,3,5-trien-1-yl)acridin-10-ium (C-PE7). A R2 = 0.8904 and RMSE = 0.0038 for XGBoost as performer under the random state of 38 were achieved. Both models, XGBoost and RF identified C3-PE5 and C3-PE7 as top promising candidates, with predicted PCEs of 5.49 % and 5.43 %, respectively. By integrating DFT/cheminformatics and machine learning techniques, this study enabled PCE prediction with no need for experimental input.

Overcoming Fe(III) precipitation barrier in acid mine drainage via a visible light-assisted photo-electrochemical system

Acid mine drainage (AMD) is characterized by high concentrations of Fe(II) and Fe(III), which can be harnessed for the in-situ formation of schwertmannite, enabling the efficient immobilization of toxic heavy metals. However, existing biological and chemical methods for schwertmannite synthesis face significant challenges, including low Fe(II) oxidation rates and particularly limited Fe(III) precipitation efficiency in acidic environments. In this study, we develop a visible light-assisted photo-electrochemical (PEC) system that effectively overcomes these barriers. By leveraging anodically evolved O2 and cathodically generated OH-, we achieved facile Fe(II) oxidation at pH 3.0, and an impressive Fe(III) precipitation efficiency of 82.8 %, significantly exceeding the < 30 % efficiency reported by other methods. Mössbauer spectroscopy and X-ray diffraction confirmed that the generated minerals are high-purity schwertmannite. Experimental and theoretical analyses revealed that in the presence of cathodic alkalinity, Fe(III) undergoes further hydrolysis to form [(H₂O)3Fe(OH)2(SO4)]- species, which are thermodynamically capable of spontaneous polymerization and mineralization. Furthermore, the photoreduction of [(H₂O)4Fe(SO4)2]- within the PEC system, followed by subsequent oxidation, plays a crucial role in facilitating Fe(III) mineralization. The PEC system also effectively transformed As(III) to As(V) and Cr(VI) to Cr(III) in AMD, promoting their immobilization in the resultant schwertmannite.

Water-based green deep eutectic solvent: Application in liquid-liquid microextraction of trace bisphenol A in edible oils

In this study, tetrabutylammonium chloride (TBAC), tetrabutylammonium bromide (TBAB), and choline chloride (ChCl) were innovatively applied in the liquid-liquid microextraction (LLME) of bisphenol A (BPA) from edible oil by forming water-based deep eutectic solvent (WDES). The presence of water is not only used in the synthesis of WDES, but also modulates the viscosity of DES and improve its diffusion and mass transfer properties. Several crucial parameters affecting the extraction efficiency were examined, including the type and amount of WDES and the extraction time. The results indicated that TBAC-H2O (molar ratio 1: 5) WDES exhibited the best extraction ability, the optimal extractant dosage was 100 μL and the extraction time was 3 min. Under the optimized experimental conditions, the proposed method showed a low detection limit (0.2 ng mL-1), good linearity (R2 = 0.997), precisions (RSDs ≤5.1 %) and was successfully employed to detect BPA in edible oil with excellent recoveries (90.6-102.6 %). The formation of the WDES was confirmed by 1H NMR, differential scanning calorimetry (DSC). The extraction mechanism was explored through theoretical calculations and Attenuated Total Reflection Fourier Transform Infrared spectroscopy (ATR-FTIR) analysis. The results revealed that the separation of BPA by WDESs was primarily dominated by hydrogen bonds, and the hydrogen bond interaction between TBAC-BPA was stronger than that of TBAB-BPA and ChCl-BPA. This work provides a valuable reference for the determination of trace BPA in edible oils or similar samples in food safety monitoring and screening.

QM/MM investigation of the discriminatory pre-transfer editing mechanism operated by Lysyl-tRNA synthetase

Aminoacyl-tRNA synthetases (aaRSs) are essential enzymes that remarkable facilitate the aminoacylation process during translation. With a high fidelity, the mischarged tRNA is prevented through implementing pre- and post-transfer proofreading mechanisms. For instance, Lysine-tRNA synthetase charges the native substrate, lysine, to its cognate tRNA. In spite of the great structural similarity between lysine to the noncognate and toxic ornithine, with the side chain of lysine being only one methylene group longer, LysRS is able to achieve this discrimination with a high efficiency. In this work, the hybrid quantum mechanics/molecular mechanics (QM/MM) investigation was applied to probe the pre-transfer editing mechanism catalyzed by lysyl-tRNA synthetase to reject the noncognte aminoacyl, L-ornityl (Orn), compared to the cognate substrate, L-lysyl. Particularly, the self-cyclization pre-transfer editing mechanism was explored for the two substrates. The substrate-assisted self-cyclization editing of Orn-AMP, where its phosphate moiety acts as the catalytic base, is found to be the rate-determining step with an energy barrier of 101.2 kJ mol-1. Meanwhile, the corresponding rate-limiting pathway for the native Lys-AMP lies at 140.2 kJ mol-1. This observation clearly indicated the infeasibility of this catalytic scenario in the presence of the native substrate. Interestingly, a thermodynamically favorable cyclic product of -92.9 kJ mol-1 with respect to the aminoacyl reactant complex demonstrated evidence of a successful pre-transfer editing. This reaction resulted in the discharge of the on-cognate -ornithine derivative from LysU's active site. These valuable mechanistic insights are valuable to enrich our knowledge of this extremely efficient and specific catalytic machinery of LysRS.

Characterization of Larvicidal Diterpene Resin Acids in Melipona quadrifasciata Geopropolis via LC-ESI-MS/MS, GC-MS and Computational Analysis

RATIONALE

Dengue, an arboviral disease transmitted by the Aedes aegypti mosquito, is a major global public health problem challenge. Insecticides based on natural products can provide a good alternative to synthetic agents, as they are safer for both the environment and human health. This study evaluated the activity of geopropolis from stingless bees and Apis mellifera bees on Ae. aegypti, using mass spectrometry approaches to identify compounds with larvicidal potential against Ae. aegypti.

METHODS

The larvicidal activity of propolis from stingless bees and A. mellifera, as well as the Melipona quadrisfasciata geopropolis (a mixture of soil/clay and propolis), was evaluated against Ae. aegypti larvae (Rockefeller strain). ESI-MS/MS analyses were performed using a quadrupole/time-of-flight mass spectrometer for all geopropolis samples, the geopropolis from Melipona quadrifasciata was also analyzed using an ion trap instrument. The ESI-qTOF-MS/MS data were processed in a spectral similarity network using GNPS. Molecular annotation of potential compounds was performed using the in silico tool called NAP. Gas-phase fragmentation mechanisms were proposed in conjunction with computational chemistry studies. Silylated geopropolis samples were also analyzed by GC-MS.

RESULTS

Geopropolis from the stingless bee M. quadrifasciata caused 90% and 100% mortality in Ae. aegypti larvae after 24 and 48 h of exposure, respectively, exhibiting the highest activity. Mass spectrometry-based molecular network approach supported the suggestion of discriminant compounds between active and inactive samples. The combination of NAP predictions with gas-phase reactions from ESI-MS/MS and EI-MS data facilitated the annotation of larvicidal compounds, including diterpene resin acids, such as dehydroabietic acid and its derivatives, abietic acid, and pimaranes.

CONCLUSION

The combination of HPLC-MS/MS and GC-MS data suggests that diterpene resin acids contribute to the larvicidal effect of M. quadrifasciata geopropolis on Ae. aegypti, enhancing our understanding of potentially bioactive natural products against the arbovirus vector.

Theoretical insights on the double ESIPT mechanism and fluorescence properties of H2BIo chromophore

2-{[3-(1H-benzoimidazol-2-yl)-2-hydroxy-5-methylbenzylidene] amino}-benzoic acid (H2BIo) based on proton transfer can serve as the fluorescent probe for detecting heavy metal ions. The excited-state intramolecular proton transfer (ESIPT) reaction mechanism of the H2BIo chromophore with an intramolecular asymmetric double hydrogen bond in different solvents are investigated. The reaction barrier of the ESIPT along hydrogen bond O1-H2···N3 is higher than that of ESIPT along O4-H5···N6, which indicates that the double ESIPT is a stepwise process. The time-evolving non-adiabatic excited-state dynamic simulations shows that the sequence ESIPT reactions on a time scale: the ESIPT along O1-H2···N3 is faster than the ESIPT along O4-H5···N6. The analyses of electron structure and spectra indicate that the double ESIPT couples with electron transfer, significantly enhances the fluorescence signal, thereby improving the performance of the fluorescent probe in detecting heavy metal ions.

Exploring structural and spectroscopic aspects, solvent effect (polar and non-polar) on electronic properties, topological insights, ADME and molecular docking study of thiocolchicoside: A promising candidate for antiviral and antitumor pharmacotherapy

Thiocolchicoside (TCS), a colchicine derivative, was analyzed using experimental and theoretical spectroscopic methods. The bond angle C24-C30-C32 showed a simulated value of 136.0° and an observed value of 132.9°, higher than the standard value of 120°, due to the electronic or steric effects of the oxygen atom (O10). The vibrational spectra identified the stretching and deformation modes of several functional groups, including O-H, N-H, C-H, CH2, CH3, CO, C-O, C-C, and C-S. In polar solvents like water, DMSO, and acetone, the HOMO and LUMO energies were more stabilized compared to non-polar solvents like toluene, indicating stronger solvent-solute interactions. The FMO energy gap was largest in water and DMSO (3.53 eV) and smallest in toluene (3.51 eV), suggesting greater reactivity in non-polar solvents. Electron donation by nitrogen (N12) and oxygen (O10) lone pairs to the electron acceptors O11-C34 and N12-C34 resulted in the highest stabilization in NBO analysis, with energies of 44.62 and 25.34 kJ/mol, respectively, due to L(2)-π* and L(2)-σ* transitions. Topological analysis showed hydrogen atoms H54 and H43 in the sugar moiety, methoxy (O-CH3), and acetyl (CO-CH3) marked in red, indicating electron localization, while blue around C13, C15, and C32 indicated delocalized electron regions. ADME prediction shows that TCS has low GI absorption and no permeability across the BBB, with five hydrogen bond donors and ten acceptors. Molecular docking analysis confirmed TCS's biological activity, demonstrating binding affinities for COVID-19 main proteases 6LU7, spike protein 6VXX, and SMAD proteins 1U7V (SMAD4) and 1U7F (SMAD3) with binding energies of -9.52, -3.59, -5.18, and -5.85 kcal/mol, indicating its potential antiviral and antitumor effects.

Chalcones derived from Croton anisodontus as potential anticancer agents against human cancer cell lines SNB-19 (glioblastoma), HCT-116 (colon), and PC3 (prostate)

Chalcones are a class of natural or synthetic compounds with an α, β-unsaturated carbonyl system. From a pharmacological standpoint, they are highly promising substances, particularly due to their diverse pharmacological properties, among them anticancer activity. The present study aims to evaluate through in vitro and in silico studies the cytotoxicity of chalcones derived of the natural product 2-hydroxy-3,4,6-trimethoxyacetophenone isolated from Croton anisodontus, in order to identify compounds with greater antitumor activity. Regarding the cytotoxic activity, it was observed that these chalcones exhibited activity in human cancer cells of colon (HCT-116), prostate (PC3) and glioblastoma brain (SNB-19). The results demonstrated that chalcone containing a fluorine atom at the para position in the B-ring displayed more significant activity against tumor cell lines PC-3 (IC50 = 4.79 ± 0.72 μM), HCT-116 (IC50 = 3.94 ± 0.4 μM) and SNB-19 (IC50 = 3.64 ± 0.69 μM). Molecular docking study confirmed that the synthesized chalcones interacted in the same region of the binding site of the AQ4 inhibitor against HCT-116 and the 6VN inhibitor against SNB19, indicating which have a similar action to the co-crystallized inhibitors, in addition to competing with testosterone against PC-3, since they interact with residues of the Ligand Binding Domain (LBD). In silico study of absorption, distribution, metabolism, and excretion (ADME) showed that chalcones have high cellular permeability, are slightly soluble in water and moderately bound to plasma proteins, which are essential characteristics of compounds that present antitumor activity. Thus, the chalcones derived from Croton anisodontus could be promising prototypes for development new anticancer drugs.

Electronic properties and adjuvant effect of riparins I-IV: Inhibition of β-lactamase and QacC efflux pump in Staphylococcus aureus K4100

Staphylococcus aureus is a leading cause of nosocomial infections, posing a significant health threat due to its resistance mechanisms, particularly involving β-lactamase enzymes and efflux pumps. Targeting these mechanisms is crucial to restore the efficacy of antibiotics. This study characterized the electronic properties of riparins I, II, III, and IV and evaluated their effects on the β-lactamase enzyme and the QacC efflux pump in the S. aureus K4100 strain. The electronic properties of the riparins revealed distinct electrophilic characteristics, but similar nucleophilic behavior, as indicated by the HOMO (Highest Occupied Molecular Orbital) and LUMO (Lowest Unoccupied Molecular Orbital) orbital energy values. Microbiological testing showed that riparins I, II, III, and IV did not display direct antibacterial activity against S. aureus K4100. However, riparin III significantly reduced the MIC of oxacillin, suggesting it potentiates the antibiotic's effect, likely by targeting the β-lactamase enzyme. Furthermore, riparins II and III lowered the MIC of ethidium bromide, indicating their potential as inhibitors of the QacC efflux pump. These findings highlight the potential of riparins II and III as adjuvants to enhance the effectiveness of antibiotics against multidrug-resistant strains of S. aureus.

Ingeniously regulating the conformational equilibrium and ESPT mechanism of HBT-DPI by solvent environment: A novel perspective

HBT-DPI was a single-molecule multi-conformational fluorescent material and had unique applications for hydrophobic/hydrophilic mapping on large-scale heterogeneous surfaces. In this paper, the different proton transfer processes and luminescence mechanisms of HBT-DPI in Dichloromethane (DCM, no hydrogen bond (HB) receptor) and N, N-Dimethylformamide (DMF, HB receptor) solvents were systematically studied. Using the quantum chemistry method, the stable structures of HBT-DPI in two solvents were determined based on the Boltzmann distribution. The analysis related to HBs parameters and charge distribution confirmed the HBs strength variation and ICT properties of HBT-DPI after photoexcitation. We confirmed that HBT-DPI underwent the stepwise (A → B → C) excited state double proton transfer (ESDPT) process in DCM. Whereas, HBT-DPI underwent the excited state intramolecular proton transfer (ESIPT) process in DMF, with the weakened intramolecular hydrogen bond (IAHB) after photoexcitation. By simulating the fluorescence spectra in the two solvents, we attributed the fluorescence in the experiment of DCM to the S1 state radiation. In DMF, the fluorescence of the S1 and PT states jointly contributed to the fluorescence band at 500 nm observed in the experiment. Furthermore, the hole-electron analysis indicated that the fundamental reason for fluorescence quenching of HBT-DPI in DCM was the charge decoupling effect. Our work provided a comprehensive and systematic explanation of the different proton transfer mechanism and luminescence characteristic for HBT-DPI in two kinds of solvents. On this basis, we furnished the theoretical guidance and reference for its application in hydrophobic/hydrophilic monitoring and measurement.

Synthesis of fluorescent dicyanomethylenevinyl-1,3-dicoumarin compounds with donor-acceptor-π-donor (D-A-π-D) system and investigation of their photophysical, NLO, and chemosensor properties: Part 1

Coumarin compounds have heterocyclic core with different properties such as high quantum yields, broad Stokes shifts, and superior photophysical and biological activity. It is known that fluorescence properties increase with increased intramolecular charge transfer in systems where electron-withdrawing or donor groups are attached to different positions of the coumarin compound. When these compounds interact with analytes in the environment, the analytes in the environment can be detected by quenching or increasing fluorescence. For this purpose, dicyanomethylenevinyl-1,3-dicoumarin compounds were obtained and 1H NMR, 13C NMR, FT-IR, HR-MS elucidated their structures. To determine the photophysical properties of the synthesized compounds, absorption, and emission spectra were examined in solvents with different polarities, and also quantum yields and Stokes shifts were calculated. Additionally, the sensitivity/selectivity properties of the compounds towards various anions were investigated by spectrophotometric, spectrofluorometric, and 1H NMR titration methods. The limit of detection (LOD) of the sensors to sense cyanide anion was considered based on absorption titration. The pKa value of compound that could be pH sensor candidate was determined. Thermogravimetric analysis was performed as an important parameter for compounds in electro-optical (EO) systems. Additionally, nonlinear optical (NLO) properties of the compounds were calculated experimentally and theoretically. The some experimental results were explained by Density Functional Theory (DFT) and time-dependent DFT (TDDFT) calculations.

Spectroscopic characterization of radicals formed by hydrogen-atom abstraction from γ-valerolactone and γ-butyrolactone

γ-valerolactone (GVL) and its unmethylated counterpart, γ-butyrolactone (GBL), are important compounds with a wide range of potential uses. For example, GVL is proposed as an ideal alternative renewable energy source, while GBL can be utilized as an electrolyte. Understanding the combustion mechanisms of these compounds is crucial for optimizing their use as energy sources and monitoring the products formed during combustion. During pyrolysis, reactions with hydrogen atoms play a key role. Although the reactions of lactones with hydrogen atoms have been studied at higher temperatures using theoretical and computational methods, the spectroscopic data for the radicals produced during these reactions remain incomplete. Such data could, however, be valuable for tracking radical mechanisms. This study investigated these reactions at 3.1 K using the para-H2 matrix-isolation technique. The conditions provided by this method are particularly well-suited for studying radicals, in contrast to the conditions used in pyrolysis studies. IR spectroscopy was employed to monitor the reactions, enabling us to observe the vibrational spectra of the resulting radicals. These spectroscopic data could offer valuable insights for further exploring the combustion processes of GVL and GBL.

Molecular vibrations of acetylacetone enol. Infrared polarization spectroscopy and theoretical predictions

The IR polarization spectrum of acetylacetone enol (AAe, (3Z)-4-hydroxy-3-penten-2-one) was recorded in the region 2000 - 450 cm-1 using stretched polyethylene as an anisotropic solvent. The measured orientation factors were consistent with Cs molecular symmetry of AAe and provided an experimental distinction between in-plane and out-of-plane polarized spectral features. The results suggest the assignment of at least one previously unrecognized fundamental transition. Excellent agreement with presently and previously observed transition wavenumbers in the investigated region was obtained by theoretical predictions in the harmonic approximation using B3LYP-D3 Density Functional Theory (DFT); calculated diagrams are provided for all 39 normal modes of AAe. The prediction of in-plane transition moment directions was found to be very sensitive to calculational details. The wavenumbers computed with the anharmonic models VPT2 (2nd-order Vibrational Perturbation Theory) and DVPT2 (Deperturbed VPT2) were consistent with those of the harmonic analysis, but the predictions obtained using GVPT2 (Generalized VPT2) deviated significantly.

Phase transformation of calcium sulfate at mineral-solution interface: An overlooked pathway for selective enrichment of cadmium

The reactions at the mineral-solution interface govern whether heavy metals (HMs) ions are retained within minerals or migrate with the solution, thus influencing their cycling and fate. However, the mechanisms driving this differential behavior of HMs at the interface remain poorly understood. In this study, we present a novel paradigm for the selective retention of HMs ions at the mineral-solution interface. By confining the solution on the mineral surface to a defined volume, specifically thinning it down to a thickness of 50 nm, selective retention of Cd ions in the presence of coexisting Cu and Zn ions was achieved. The distribution coefficient of Cd in the mineral reaches as high as 41.44, significantly exceeding that of Cu at 0.13 and Zn at 0.07. Combined with DFT calculations, the results reveal that this selectivity arises from the regulation of the ion desolvation free energy by the solution nanofilm, precisely compensating the energy cost for Cd incorporation as an impurity into the mineral lattice. This work not only enriches the understanding of ion separation behavior at natural mineral-solution interfaces but also offers a new strategy for heavy metal separation and enrichment in industrial applications.

Structural and dynamical investigation of glassforming smectogen by X-ray diffraction and infra-red spectroscopy aided by density functional theory calculations

Molecular arrangement in the chiral smectic phases of the glassforming (S)-4'-(1-methylheptylcarbonyl)biphenyl-4-yl 4-[7-(2,2,3,3,4,4,4-heptafluorobutoxy) heptyl-1-oxy]benzoate is investigated by X-ray diffraction. An increased correlation length of the positional short-range order in the supercooled state agrees with the previous assumption of the hexatic smectic phase. However, the registered X-ray diffraction patterns are not typical for the hexatic phases. Comparison of the smectic layer spacing and optical tilt angle indicates a strongly non-linear shape of molecules, which enables choice of the molecular models obtained by DFT calculations, used subsequently to interpret the infra-red spectra. The presumption of the hexatic smectic FA* or IA* phase is supported by the splitting of the absorption bands related to the CO stretching in the supercooled state, which is absent in the smectic CA* phase above the melting temperature. The glass transition affects the temperature dependence of the smectic layer spacing but only subtly impacts the infra-red spectra. Application of the k-means cluster analysis enables distinction between the infra-red spectra below and above the glass transition temperature, but only for certain spectral ranges.

Unusual Tautomerism of Methyl Allophanate: Selective Crystallization of the Minor Component via Hydrogen-Bond Network

The unexpected tautomerism of methyl allophanates has been observed in the solid state. X-ray analysis, IR/UV spectroscopic data, and density functional theory (DFT) calculations showed that the molecule adopts an imidic form in the crystal, whereas the amide form, which is more stable in aqueous solution, is expected. The imidic form in the solid state is stabilized by a robust hydrogen-bond network, which facilitates the selective isolation of minor imidic species.

Decentralized Metal-Metal Bonding in the AuNi(CO)4- Anion Described Equally Well with Dative Bonding as with Electron-Sharing Bonding

The heterodinuclear AuNi(CO)4- complex is scrutinized in the gas phase by using mass-selected anionic photoelectron velocity-map imaging spectroscopy in conjunction with theoretical computations. The ground state of AuNi(CO)4- is characterized to have an Au-Ni bonded structure, consisting of an AuCO fragment attached to the Ni center of the Ni(CO)3 fragment. Comprehensive quantum chemical studies reveal that the AuNi(CO)4- complex at equilibrium structure features a decentralized bonding scenario, where the exotic metal-metal σ bonding may be equally well described with dative bonding as with electron-sharing bonding between two fragments.

Quantum Chemical Density Matrix Renormalization Group Method Boosted by Machine Learning

The use of machine learning (ML) to refine low-level theoretical calculations to achieve higher accuracy is a promising and actively evolving approach known as Δ-ML. The density matrix renormalization group (DMRG) is a powerful variational approach widely used for studying strongly correlated quantum systems. High computational efficiency can be achieved without compromising accuracy. Here, we demonstrate the potential of a simple ML model to significantly enhance the performance of the quantum chemical DMRG method.

Role of explicit solvation and level of theory in predicting the aqueous reduction potential of carbonate radical anion by DFT

Chemical oxidation reactions, a key class of electron transfer processes, have broad applications, including the treatment of persistent and mobile pollutants. Marcus theory, paired with density functional theory (DFT) simulations, enables quantification of thermodynamic properties in these reactions. However, accurately modeling species with complex solvent interactions, especially radicals, requires careful selection of computational methods. Reduction potentials provide critical benchmarks for evaluating solvent models and functional choices by comparing simulated values to literature data. In this study, we used the carbonate radical, known for its strong intermolecular interactions, as a model to assess solvation models and computational functionals. Implicit solvation methods significantly underperformed, predicting only one-third of the measured reduction potential. Accurate results were obtained using explicit solvation with 18 water molecules for ωB97xD/6-311++G(2d,2p) and 9 water molecules for M06-2X/6-311++G(2d,2p). B3LYP/6-311++G(2d,2p) showed improvement with additional explicit solvation but failed to match literature benchmarks. Functional performance differences, analyzed through natural bond orbital (NBO) and charge transfer calculations, emphasized the critical role of dispersion corrections. Testing various dispersion correction methods revealed consistent improvements in reduction potential accuracy. These findings highlight the necessity of explicit solvation for modeling electron transfer reactions with extensive solvent interactions and underscore the importance of selecting appropriate functionals and dispersion corrections for reliable predictions.

Exciton Transfer Simulations in a Light-Harvesting 2 Complex Reveal the Transient Delocalization Mechanism

The striking efficiency of exciton transfer in light-harvesting (LH) complexes has remained a topic of debate since the revision of the long-held role of electronic coherences. To address this issue, we have developed a neural network for the pigments in the LH2 complex of Rhodospirillum molischianum that allows nonadiabatic molecular dynamic (NAMD) simulations of exciton transfer in a coupled quantum mechanical/molecular mechanics (QM/MM) embedding. The calculated exciton occupations are averaged over hundreds of trajectories, each lasting several picoseconds. We have obtained transitions within the B800 and B850 rings that agree well with the experimental results, indicating an incoherent hopping process in the B800 ring and a more delocalized transfer in the B850 subsystem. The reorganization energies and excitonic couplings are comparable to each other, indicating that the "transient delocalization" transport model is the underlying cause of the highly efficient exciton transport in the B850 ring. This phenomenon can be attributed to a localized exciton that shows occasional large delocalization events. Our results indicate that the reason for the striking efficiency is the unusual electronic property of bacteriochlorophyll, manifested in minimal inner and outer sphere reorganization energies.

Interaction of Small Nitriles Occurring in the Atmosphere of Titan with Metal Ions of Meteoric Origin

Meteoric material injected into the atmosphere of Titan, Saturn's moon, can react with nitriles and other organic compounds that constitute Titan's atmosphere. However, specific chemical outcomes have not been fully explored. To understand the fates of meteoric metal ions in the Titan environment, reactions of Mg+ and Al+ with CH3CN (acetonitrile) and C2H5CN (propionitrile) were carried out using a drift cell ion reactor at room temperatures (300 K) and reduced temperatures (∼193 K) and modeled using density functional theory and coupled-cluster theory. Analysis of reactant ion electronic state distributions via electronic state chromatography revealed that Mg+ was produced in our instrument exclusively in its ground (2S) state, whereas Al+ was produced in both its 1S ground state and 3P first excited state. Mg+(2S) and Al+(1S) produce association products exclusively with both CH3CN and C2H5CN. Primary association reactions with C2H5CN occurred with higher reaction efficiencies than those with CH3CN. Mg+(2S) sequentially associates up to four nitrile ligands, and Al+(1S) associates up to three, each via the nitrile nitrogen. Computed binding energies are strongest for the first ligand and diminish with subsequent nitriles. Mg+(2S) exhibits a stronger preference for binding nitriles than Al+(1S) because its unpaired electron delocalizes to the nitrile ligands through back-bonding, whereas the lone pair on Al+(1S) remains localized on the metal center. Al+(3P) exhibited evidence of bimolecular product formation with both nitriles. Computational modeling of Al+(3P) with CH3CN suggests that the major product, AlCH3+, is kinetically favored over the more energetically stable product, Al+(HCN).

Stability of polycyclic aromatic hydrocarbons on graphite: resistance to horizontal displacement

The stability of adsorbed molecules on surfaces depends on the magnitude of adsorbate-substrate interaction energies and the resistance of these molecules to horizontal displacement. Therefore, it is essential to analyse both interaction energy (Eint) and its change with horizontal displacement (ΔEint). In physisorbed monolayers at a highly oriented pyrolytic graphite (HOPG)/solvent interface, molecular building blocks often contain both aromatic and alkyl chain moieties, as aromatic molecules without additional substituents are difficult to observe via scanning tunnelling microscopy. This suggests that aromatic molecules have less adsorption stability on the HOPG than n-alkanes, though the underlying reason remains unclear. In this study, we performed dispersion-corrected density functional theory calculations to evaluate Eint and ΔEint of polycyclic aromatic hydrocarbons (PAHs) on a graphite model surface (C96H24). ΔEint was analysed for PAHs with the number of carbon atoms (Nc) from 6 to 24. The maximum ΔEint (ΔEint(max)) is related to the barrier height for lateral migration. The ΔEint(max) per Nc showed directional dependence and ranged from 0.015 to 0.20 kcal mol-1, with the largest value for PAHs being about two-thirds that of n-alkanes (0.30 kcal mol-1), indicating greater mobility of the former. These findings demonstrate that aromatic and alkyl chain moieties in two-dimensional assemblies exhibit distinct resistance against horizontal migration. The preferential role of alkyl chains suggests that molecular assemblies align with the graphite lattice, prioritising alkyl unit positioning over aromatic orientation.

Isomerism and Solvent Interaction in Octamethyl Calix[4]pyrrole Complexed with Formate

We investigate the binding motifs of host-guest complexes of the anion receptor octamethyl calix[4]pyrrole (omC4P) with the formate anion using cryogenic ion vibrational spectroscopy in concert with density functional theory. The resulting infrared spectrum in vacuo is compared to that in deuterated acetonitrile and acetone solutions. The combination of the strong host-guest interaction and the charge distribution that the formate ion presents to the chemical environment results in complex behavior of the NH stretching features in the two solvents. The formate-omC4P complex has three low energy isomers in vacuo: (i) one with an oxygen atom of formate interacting with three of the NH groups of omC4P and the other oxygen atom interacting with the remaining NH group; (ii) one with a single oxygen atom of formate interacting with all four NH groups of omC4P; and (iii) one with each oxygen atom interacting with two NH groups. Each complex geometry lowers the C4v symmetry of the receptor to C1, Cs, or C2v, respectively, and both symmetry breaking and isomerism are reflected in the pattern and broad line shapes of the NH stretching modes of omC4P.

Local-Density Correlation Functional from the Force-Balance Equation

The force-balance equation of time-dependent density-functional theory presents a promising route toward obtaining approximate functionals; however, so far, no practical correlation functionals have been derived this way. In this work, starting from a correlated wave function proposed originally by Colle and Salvetti [Theoret. Chim. Acta 37, 329 (1975)], we derive an analytical correlation-energy functional for the ground state based on the force-balance equation. The new functional is compared to the local-density correlation of the homogeneous electron gas, and we find an increased performance for atomic systems, while it performs slightly worse on solids. From this point onward, the new force-based correlation functional can be systematically improved.

Conformational Control as a Design Strategy to Tune the Redox Behavior of Benzotriazole Negolytes for Nonaqueous Flow Batteries

Here, we present a molecular engineering strategy to tune the reduction potentials of benzotriazole derivatives as high-energy-density negolytes in nonaqueous redox flow batteries. Within nonaqueous electrolytes, these derivatives, notably 2-(o-tolyl)-2H-benzo[d][1,2,3]triazole (1), demonstrate a theoretical capacity of up to 93.8 Ah L-1 and a reduction potential of -2.35 V vs ferrocene/ferrocenium (Fc/Fc+). Introducing dimethyl substitution (i.e., 2-(2,6-dimethylphenyl)-2H-benzo[d][1,2,3]triazole (4)) shifts the reduction potential even more negatively to -2.55 V vs Fc/Fc+. We ascribe the nonlinear effect of dimethyl substitution on reduction potential to ground-state conformational effects. Flow battery tests with negolyte 1 and ferrocene posolyte demonstrated >90% Coulombic efficiency at 6.7 mA cm-2 with improved cyclability in the presence of lithium bis(trifluoromethylsuylfonyl)imide supporting salt.

Excited-state proton transfer in the rare isoguanine-isocytosine base pair in water solution

CONTEXT

With the current research, we aim to study the mechanism of the excites state proton transfer (ESPT) between the nucleobases isoguanine (iG) and isocytosine (iC) in their Watson-Crick model. Such research is proposed for the first time and it can partially reveal the question why the nature "has chosen" guanine and cytosine for pairing in the DNA duplex and not their analogs (isoforms). The UV irradiation of the water solution of equimolar mixture of iG and iC implies a tautomeric conversion between the nucleobases. In the research, the mechanism of the ESPT was followed and clarified for the first time. All this reflects to the photostability of the iG-iC base pair in water solution.

METHODS

For the purposes of the current research, we chose to use the TD DFT with the hybrid functional B3LYP in combination with the aug-cc-pVDZ basis set. The water surroundings are modeled according to the polarizable continuum model (PCM) modeling the solvation effects on the studying systems. Linear interpolation and intrinsic reaction coordinate approach were applied for the reaction path follow of the ESPT.

Supramolecular Organization in Monolayers of Pyrene-Functionalized Asymmetric Twist-Bend Nematic Dimers: Comparison with a Three-Dimensional Crystal Structure

Two-dimensional (2D) supramolecular organization of asymmetric liquid crystal dimers containing two chemically different mesogenic groups, namely, cyanobiphenyl and pyreneiminomethyl phenoxy groups, linked with an oligomethylene linker of different length (six or eight -CH2- units), was studied using scanning tunneling microscopy. For this purpose, monolayers of these dimers were deposited on an HOPG substrate from their solutions in hexane by drop-casting and imaged at nanometer resolution after drying. A detailed discussion of two possible different supramolecular organizations is presented. In the case of the first one, termed the "lamellar structure", the molecules in each layer are arranged in parallel molecular rows. Comparative analysis of the monolayer structure with already reported XRD data on 3D organization of the same molecules in a single crystal revealed significant differences resulting from (i) different ordering preferences in 2D and 3D systems and (ii) effects of the interactions of the deposited molecules with the graphite substrate. A small extension of the linker by two methylene groups does not change the type of ordering in the monolayer but causes an extension of the unit cell in one direction, indicating that the lamellar structure is stabilized by rows of densely packed large aromatic pyrene units. Studies of the derivative with a longer linker (containing eight -CH2- units) also showed the possibility of the occurrence of an alternative type of its monolayer organization, termed here "aggregate structure". In this case, the monolayer consists of ordered aggregates of two molecules. According to the authors' knowledge, this type of structural organization has not yet been reported for this family of compounds. It is, however, qualitatively consistent with the already described supramolecular ordering in CBO5O.Py (CCDC 2019485), a compound closely resembling the dimers studied in this research.

Interexcited State Photophysics II: A Qualitative Excited State Dynamics Model from First-Principles

In Part I of this series [J. Chem. Theory Comput. 2023, 19(1), 271-292], a benchmarking study of nuclear-electronic couplings was performed using 15 density functionals across two basis sets. From these, five density functional and basis set combinations (data sets) yielded results that agreed with experiments for the S1 → S0 internal conversion (IC) rate in perylene. In this Part II, we use those five data sets to calculate the excited state dynamics in perylene up to the second excited state within a density functional theory (DFT) framework. Interexcited state IC was found to be generally overestimated by 10 orders of magnitude at ∼1020 s-1 in the best case for the S2 → S1 pathway. Probing of the methodology using a multireference method found DFT to overestimate the nuclear-electronic coupling between excited states, with CASSCF(8,8) overestimating the IC rate by 3 orders of magnitude in the best case. Therefore, we applied a faux-damping function, which reduced the rates by 10 orders of magnitude on the singlet manifold and 20 on the triplet manifold. With this correction, the IC rate constants for S2 → S1 compared well to the experimental value of 302 ± 5 fs calculated in this work. Photoluminescence quantum yields (PLQYs) and anti-Kasha quantum yields (AKQYs) were calculated; the PBE0/def2-TZVP data set yielded the most accurate PLQY and AKQY (0.907 and 5.07 × 10-5, respectively). Although there is room for refinement in the method, we have shown a qualitative prediction of the excited state dynamics of perylene.

Functional nanocellulose hydrogel with amino acid integration for enhanced Li/Fe separation in LiFePO4 batteries

With the rising prevalence of lithium-ion batteries, efficient recovery of metal ions, particularly those potentially released from LiFePO4 anodes, has become critical. Given that both Fe3+ and Li+ ions can form electrostatic adsorptive interactions, achieving effective separation of conventional adsorbent materials becomes challenging. This study presents an amino acid-functionalized nanocellulose hydrogel (ANH) synthesized by incorporating L-threonine, which significantly enhances the selective adsorption of Fe3+ in a mixed-ion environment by leveraging coordination differences between Li+ and Fe3+. The morphology, functional groups, and pore structure of ANH were extensively characterized using scanning electron microscopy, Fourier transform infrared spectroscopy, and mercury intrusion porosimetry techniques. Through batch experiments, the adsorption thermodynamics and isotherms of ANH for Fe3+ were examined. Furthermore, the adsorption selectivity of ANH for Li+ and Fe3+ was evaluated in a mixed-ion system, revealing that the adsorption capacity for Fe3+ was four times higher than for Li+ at elevated concentrations. The adsorption mechanism of Li+/Fe3+ was elucidated through multi-scale simulations, and the influence of varying amino acid grafting degree on adsorption metrics, such as solvent-accessible area and hydrogen bonding numbers, was investigated. The combination of experimental and theoretical results demonstrates the potential of ANH to inform the development of high-performance, selective adsorbents.

Carbon NMR Titration Could Be More Informative for In-Situ Lanthanide Coordination Chemistry Investigation

In situ characterization of coordination species and their evolution are crucial for effective lanthanide separation and recycling. Current technical approaches often operate under constrained conditions, requiring complex equipment, experimental setups, and sometimes intricate data interpretation. Herein, we demonstrate that carbon NMR titrations offer a valuable approach for in situ coordination analysis of lanthanides, particularly for highly fused preorganized ligands that offer more NMR-active carbons than traditional proton NMR. Two representative ligands of both lipophilic and hydrophilic in nature were investigated, and the resulting carbon NMR titration data were analyzed. Comparisons with IR and single-crystal data showed that NMR provided insights not only into the evolution of coordination species but also into changes in the electron distribution during complex formation. Additionally, we discussed inconsistencies between atomic charge populations obtained from carbon NMR and those from Mulliken and Hirshfeld calculations. With advancements in NMR technology and the availability of higher-field NMR instruments, we believe NMR titrations will play an increasingly significant role in unravelling the complex solution coordination chemistry of f-block elements.

Mechanisms and dynamics of the halophilic reaction between CH2CN- and CCl4

In gas phase experiments [H. Chen, R. G. Cooks, E. C. Meurer and M. N. Eberlin, J. Am. Soc. Mass Spectrom., 2005, 16, 2045], the reaction of the CH2CN- ion with CCl4 was observed to proceed predominantly via a halophilic reaction, where the nucleophile attacks a Cl atom, displacing the CCl3- ion, along with minor products from SN2 reactions and H/Cl exchange. In this study, the energetics of the three reaction pathways were investigated using the DFT, MP2, and DLPNO-CCSD(T) methods. The B3LYP/6-311++G** level of theory accurately described the reaction pathways compared to the DLPNO-CCSD(T)/CBS benchmark while remaining computationally efficient. At the B3LYP/6-311++G** level, the halophilic pathway was found to be barrierless and energetically favorable, whereas the SN2 pathway exhibited an energy barrier of 4.34 kcal mol-1 relative to the reactants. The H/Cl exchange reaction is proposed to occur through sequential steps: an initial halophilic pathway followed by proton transfer, due to the high energy barrier of 11.71 kcal mol-1 for the direct reaction. The reaction dynamics, investigated through bimolecular ab initio trajectory simulations at the B3LYP/6-311++G** level, revealed the formation of major halophilic products, consistent with experimental findings. Additionally, the dynamics of the SN2 reaction were explored by analyzing the post-transition state trajectories.

Aluminum Photosensitizers on Trial: Synthesis, Crystal Structures, Photophysical and Photobiological Properties of Tris(Dipyrrinato)Aluminum(III) Complexes with Long-Lived Triplet States

Metal coordination compounds are currently a focus of research in developing new photosensitizers for materials and medicinal applications. As an abundant element in the earth's crust aluminum is a suitable target element. However, only limited studies are available on its use in photoactive systems. We now report the facile preparation of a library of homoleptic tris(dipyrrinato)aluminum(III) [AL(DIPY)3] complexes. The majority of complexes was characterized by single crystal X-ray analysis and their photophysical properties upon photoexcitation and their tendency to react with the molecular oxygen of the microenvironment and generate singlet oxygen - in polar and non-polar environment was investigated. These studies are complemented by density functional theory (DFT) calculations to assess the possible electronic distribution on the frontier molecular orbitals within the complexes. As a result of charge transfer states, long-lived triplet excited states were formed and allowed for singlet oxygen generation. An initial screening of the AL(DIPY)3 complexes via in vitro phototoxicity studies against a mouse colon carcinoma cell line (CT26) was promising as these complexes were able to trigger cell death upon irradiation at nanomolar and micromolar concentrations. The results highlight the potential of aluminum dipyrrin complexes as a broadly applicable class of photosensitizers.

Degradation of AFB1 in edible oil by aptamer-modified TiO2 composite photocatalytic materials: Selective efficiency, degradation mechanism and toxicity

Most of the excessive aflatoxins in peanut oil are present at lower levels, and few photocatalysts have been reported for degrading low concentrations of aflatoxin B1 (AFB1). This study employed aptamer-modified magnetic graphene oxide/titanium dioxide (MGO/TiO2-aptamer) photocatalysts to degrade low concentrations of AFB1 in peanut oil, thoroughly investigating their selective efficiency, degradation mechanism, and product toxicity. The results indicated that the modification of aptamers on the surface of photocatalytic materials can enhance the selectivity of photocatalysts for AFB1 in peanut oil. Furthermore, UPLC-Q-Orbitrap mass spectrometry identified three degradation products, and structure properties and degradation mechanism of the composites were explored using density function theory (DFT) calculations analysis. The Ames test and zebrafish experiments confirmed that the degradation products had markedly reduced toxicity. This study offers a novel approach to mycotoxin degradation in food, crucial for reducing human exposure and ensuring food safety.