This study presents a comparative quantum-chemical investigation of five clinically used sulfonamide diuretics—furosemide, indapamide, hydrochlorothiazide, torsemide, and bumetanide—together with a focused analysis of deprotonation and local microhydration effects on furosemide. The neutral forms of the five drugs were examined using a unified density functional theory (DFT) protocol to characterize their electronic structures, dipole moments, charge distributions, and selected intramolecular closed-shell contacts. Frontier molecular orbital and conceptual DFT analyses showed that indapamide has the largest highest occupied molecular orbital–lowest unoccupied molecular orbital gap and the highest chemical hardness, whereas hydrochlorothiazide has the smallest gap, highest softness, and greatest electrophilic character. Molecular electrostatic potential mapping and Mulliken population analysis, Natural Population Analysis (NPA), and Charge Model 5 (CM5) analysis consistently localized the principal electron-rich regions on sulfonyl, carbonyl, and carboxyl oxygen atoms. Quantum theory of atoms in molecules (QTAIM) analysis identified intramolecular N–H···O hydrogen bonds in furosemide, torsemide, and bumetanide, a weaker C–H···O contact in indapamide, and a closed-shell O···Cl contact in hydrochlorothiazide. Natural bond orbital (NBO) analysis further supported the N–H···O interactions through n(O) → σ*(N–H) donor–acceptor contributions. Neutral and deprotonated furosemide were additionally examined with zero, one, or two explicit water molecules. Deprotonation altered charge localization and electrostatic characteristics, whereas microhydration produced non-monotonic electronic changes and reorganized intramolecular, drug–water, and water-mediated hydrogen-bonding patterns. The formally neutral dihydrate formed a compact, proton-transferred, strongly proton-shared network with carboxylate–hydronium-like character. Overall, protonation state and local hydration substantially modify the electronic and noncovalent-interaction landscape of furosemide.
A series of new square–planar Cu(II) complexes with deprotonated N-(pyridin-2-yl)ureas (Cu(L)2, where LH = 1,1-dialkyl-3-(4-R-pyridin-2-yl)urea) was synthesized and characterized by elemental analysis, HRMS, and IR spectroscopy. The structure of all synthesized compounds was determined by the single crystal X-ray diffraction (XRD). The supramolecular architecture is governed by the number of methyl substituents in the pyridine ring. Monosubstituted derivatives form infinite columnar stacks due to π···π stacking, whereas dimethylpyridine analogues form discrete dimers due to direct intermolecular Cu···O or Cu···C contacts. DFT calculations (QTAIM, NCI, IRI) confirmed the nature of these noncovalent interactions. The possibility of Cu/Pd isostructural substitution in such complexes is shown, which opens up additional prospects for the crystal chemical design of materials based on these ligands.
Per- and polyfluoroalkyl substances (PFAS) are one of the largest environmental concerns due to their widespread use, resistance to degradation, and risks to human health. Developing effective remediation strategies is essential yet complicated by their vast chemical diversity and unique properties. Catalytic reduction by the organometallic cofactor Vitamin B12 serves as a promising remediation strategy. Experiments have proven that B12 preferentially degrades branched PFAS but has limited success for linear PFAS. The exact reasons for this remain unknown. Understanding this structural preference could provide a critical framework for optimizing B12 facilitated degradation. This study builds upon previous work in this field by using Density Functional Theory to investigate how the complexation of PFAS to B12 changes in response to varying the oxidation state of the cobalt metal center of B12. Herein we report that in the Co2+ oxidation state, carboxylated and sulfonated PFAS, regardless of structural isomer, interact primarily by forming hydrogen bonds via their headgroup oxygens and the amino sidechains of B12. However, carboxylated PFAS interact with the metal center directly when it is Co3+. Sulfonated PFAS continue to interact via hydrogen bonds with the B12 amino groups, but the higher charge of Co3+ draws the headgroup closer, facilitating metal coordination in some configurations. Computed complexation energies indicate that as the oxidation state increases, the interaction strength also increases. Furthermore, branched isomers of carboxylated PFAS have stronger complexation energies with both Co2+ and Co3+, while sulfonated PFAS show the opposite trend.
The elements mercury, nickel and lead in nature are highly harmful to the ecosystem. The removal of mercury, nickel and lead elements from gas phase poses great challenges due to their relatively stable chemical properties and insolubility in water. Since few studies have been performed for this problem, it is imperative to develop new adsorbents to effectively remove these harmful metal elements. In this work, adsorption of Hg0, Ni2+ and Pb2+ on pure Ptn (n = 1–7) clusters, pure g-C3N4 monolayer and Ptn/g-C3N4 is studied by density functional theory (DFT) so as to clarify the effects of the support and the size of Pt clusters on adsorption of Hg, Ni and Pb elements. The results show that mercury atom is physically adsorbed on the pristine g-C3N4 surface, but chemisorbed on the Ptn clusters and the Ptn/g-C3N4 with the lower adsorption energies, shorter bond and larger charge transfer. For Hg0, Ni2+ and Pb2+ adsorbed pure Ptn clusters, the Pt7 show the strongest interactions with the lowest adsorption energies of – 0.75, − 16.47 and − 7.30 eV, and the largest charge transfer of − 0.14, 1.72 and 1.75 e, respectively. As regards Hg0, Ni2+ and Pb2+ adsorbed on Ptn/g-C3N4, the lowest Eads are − 1.53, − 19.09 and − 13.03 eV for Pt7/g-C3N4 systems, respectively. Especially, a great amount of electron cloud around the Hg, Ni and Pb elements on Pt7/g-C3N4 surface indicates their strong interaction with the surfaces in view of the enhanced charge transfer between Hg, Ni2+ and Pb2+ with the Ptn/g-C3N4 surface. Significant hybridization of Hg, Ni and Pb orbitals with the Pt orbitals within − 8 and 8 eV may substantially prompt the adsorption of these harmful metal elements in the g-C3N4 supported systems. The adsorption energies of Hg0, Ni2+ and Pb2+ on all pure Ptn clusters are higher than those of the corresponding pure g-C3N4 monolayer or Ptn/g-C3N4 systems. Therefore, it seems that Pt7/g-C3N4 emerges as a promising candidate adsorbent for the removal of mercury, nickel and lead.
The development of efficient and cost-effective electrocatalysts for the methanol oxidation reaction (MOR) is essential for advancing sustainable hydrogen production technologies. In this study, density functional theory (DFT) calculations are employed to investigate hexagonal boron nitride kekulene-like nanorings (hBNK) decorated with transition-metal (TM) single atoms (Ag, Au, Co, Cu, Fe, Ni, Pd, and Pt) as potential MOR catalysts. A controlled single-hydrogen substitution strategy enables stable anchoring of isolated metal atoms within the hBNK framework while preserving its structural integrity. Structural and energetic analyses confirm the excellent thermodynamic stability of all TM-doped systems with minimal geometric distortion. Electronic structure investigations reveal strong metal–support interactions, pronounced localization of frontier molecular orbitals on the TM centers, significant HOMO–LUMO gap narrowing, and substantial d–p orbital hybridization with neighbouring nitrogen atoms. Charge transfer and dipole moment analyses further indicate strong electronic polarization induced by single-atom decoration. Methanol adsorption is significantly enhanced on TM-doped hBNK surfaces, accompanied by bond activation and favorable charge redistribution. Free-energy calculations along the MOR pathway identify Au-, Fe-, and particularly Pt-doped hBNK as the most promising catalysts, exhibiting reduced potential-determining steps and smoother reaction energetics. These findings establish hBNK-based single-atom catalysts as robust and tunable platforms for efficient methanol oxidation and provide valuable insights for the rational design of next-generation electrocatalysts for hydrogen production.
Spiro-fused heterocycles are valuable targets in drug discovery and materials science. This study investigates how the choice of azomethine ylide precursor influences the regiochemical outcome of [3 + 2] cycloadditions with 2-arylmethylidene thiazolo[3,2-a]pyrimidines. Using acenaphthoquinone/L-proline yields a product with a 1,2-spiro junction, while isatin/L-proline affords a 1,3-isomer. Single-crystal X‑ray diffraction reveals that this regiochemical difference dictates the solid-state supramolecular architecture. The 1,2‑spiro adduct forms homochiral chains stabilized by cooperative S…O chalcogen and Br…Br halogen bonds, whereas its DMSO solvate exhibits heterochiral chains via Br···N contacts. In contrast, the 1,3‑spiro adduct is stabilized by an intramolecular S…O chalcogen bond. Notably, a survey of the Cambridge Structural Database indicates that thiazolo[3,2‑a]pyrimidine spiro compounds reported to date are predominantly 1,2‑spiro derivatives, making the 1,3‑spiro architecture described herein a rare and structurally distinctive example within this heterocyclic family. These findings highlight the potential of regiodivergent cycloadditions for engineering diverse molecular and supramolecular structures.
Finite silicon carbide nanoribbons (SiC-NRs) were systematically investigated as potential candidates for phenol removal in water treatment applications. Using density functional theory (DFT) calculations, we explored the structural, electronic, and optical properties of both unfunctionalized and functionalized SiC-NRs. Our findings reveal that unfunctionalized NRs exhibit tunable electronic properties, with edge termination playing a crucial role in modulating their bandgap and adsorption capabilities. Functionalization with carboxyl (-COOH) and amide (-CONH₂) groups significantly enhances the adsorption efficiency, binding energy, and electronic interactions with phenol molecules, with adsorption energies reaching up to − 1.52 eV for the most stable configuration (SiC₂₄-NR-s-COOH-Ph). Edge-functionalized NRs demonstrate superior phenol adsorption-desorption dynamics with shorter recovery times, making them ideal for rapid pollutant sensing and reusable filtration, while exhibiting relatively weaker adsorption energies in the range of − 0.68 to − 1.33 eV depending on the functional group and site. In contrast, surface-functionalized NRs exhibit prolonged phenol retention due to stronger charge redistribution effects, making them suitable for long-term pollutant trapping. Non-covalent interaction (NCI) and natural bond orbital (NBO) analyses confirm enhanced charge transfer and electronic stabilization in functionalized structures, particularly with -COOH groups. NBO analysis highlights dominant donor-acceptor interactions, particularly between oxygen lone pairs and SiC antibonding orbitals, leading to enhanced charge transfer and improved adsorption stability. Optical studies indicate redshifts in absorption spectra upon phenol adsorption, highlighting their potential for optoelectronic sensing. These insights demonstrate that tailored functionalization strategies can optimize SiC-NRs for efficient and selective phenol removal, offering promising avenues for advanced water purification technologies.
Indirubin derivatives are potent kinase inhibitors with considerable anticancer potential. Here, we report the synthesis and single-crystal X-ray diffraction analysis of the (R)- and (S)-enantiomers of indirubin 3’-(O-2,3-dihydroxypropyl)oxime (E804). This study aimed to elucidate the influence of the bulky, multifunctional dihydroxypropyloxime side chain on the supramolecular organization of the indirubin core. Both enantiomers crystallize in the orthorhombic chiral space group P212121. As expected for an enantiomeric pair, they form mirror-image, energetically equivalent crystal lattices. Quantitative analysis of intermolecular interaction energies using CrystalExplorer showed that both enantiomers exhibit total interaction energies from approximately − 215 to − 218 kJ/mol (which are identical within the uncertainty limit of the computational model), with lattice stabilization arising from balanced contributions of dispersion and electrostatic interactions. Comparative analysis with 5-methoxyindirubin 3’-oxime and a rhamnose-substituted derivative demonstrated that, although the 5-methoxy substituent promotes more favorable aromatic stacking geometries, the incorporation of larger multifunctional substituents, such as those in E804 and the carbohydrate analog, enhances solid-state stability through expanded dispersion-driven interaction networks despite increased lattice porosity. To the best of our knowledge, this study presents the first crystal structures of the E804 enantiomers. These findings provide valuable insights into the structure–property relationships governing indirubin derivatives and establish a rational framework for designing indirubin-based and other planar crystalline compounds with enhanced solid-state stability.
Alternamides A and B, two catechol-containing alkaloids isolated from Alternanthera littoralis P. Beauv., have been experimentally associated with the radical scavenging potency of the plant extract, but their detailed radical-scavenging mechanisms remain unclear. In this study, density functional theory calculations were performed to evaluate the antioxidant potential of alternamide A (AA) and alternamide B (AB) in aqueous and lipid-like environments. Thermodynamic descriptors, including bond dissociation enthalpy, ionization potential, and proton affinity, were analyzed to clarify the preferred formal hydrogen atom transfer, single electron transfer, and sequential proton loss electron transfer pathways. Kinetic calculations were further conducted for the reaction with the HOO• radical under physiological conditions. The thermodynamic results indicate that the hydroxyl groups are the preferred reactive sites, whereas the N–H positions are less favorable for radical scavenging. AB generally shows lower BDE, IP, and PA values than AA, suggesting stronger intrinsic antioxidant potential, particularly at the 7-OH position. At physiological pH, both compounds exist mainly in neutral forms, but their minor monoanionic populations dominate the aqueous radical-scavenging activity through the SET pathway. The overall rate constants of AA and AB in water are 1.43 × 10⁸ and 2.18 × 10⁸ M− 1 s− 1, respectively. After accounting for the molar fractions of both the antioxidant species and HOO•, the fully corrected overall rate constants are (3.59 × 105 and 5.47 × 105 M− 1 s− 1) for AA and AB, respectively, which are markedly higher than that of Trolox. In contrast, in the lipid-like medium, ionized species are less stabilized and the fHAT mechanism becomes dominant, giving lower overall rate constants of 3.14 × 10⁴ and 1.55 × 10⁴ M− 1 s− 1 for AA and AB, respectively. These findings demonstrate that alternamides A and B are efficient antioxidants in aqueous physiological environments, with AB showing superior activity, while their lipid-phase activity is moderate and mainly governed by hydrogen atom transfer.
The title compound (1E,1’E)-N, N’-(naphthalene-1,5-diyl)bis(1-(furan-2-yl)methanimine) C20H14N2O2 was synthesized via a condensation reaction between 1,5-diaminonaphtalene and two equivalents of furan-2-carboxaldehyde under mild conditions. The compound was characterized by IR, UV-Vis, 1H and 13C NMR spectroscopy, LC-ESI/MS and single-crystal X-ray diffraction. In the crystal, molecules are linked through weak C-H···N, C-H···O hydrogen bonds and van Der Waals interactions, generating a three-dimensional supramolecular network. Hirshfeld surface analysis reveals that the predominant contributions arise from H···H (38.7
During the condensation reaction of [ClP(μ-NtBu)]2 and [H2NP(μ-NtBu)]2, which generates established inorganic macrocycles [P(μ-NtBu)]2(μ-NH)4 (1) and [P(μ-NtBu)]2(μ-NH)5 (2), the acyclic cyclophosph(III)azane ‘pentamer’ (tBuNH)[[P(μ-NtBu)]25(μ-NH)4](NHtBu) (3) was isolated as a minor product. Compound 3 comprises an unprecedented, extended [P2(μ-NtBu)2]5 (open-chain) core of phosphorus‒nitrogen rings, which provides mechanistic evidence for the elusive intermediates formed during macrocyclisation to 1 and 2. The solid-state structure of the n-pentane solvate of 3 features a folded chain conformation, arranged periodically in the lattice between cross-linked hydrophobic channels. An extensive theoretical study on the conformational landscape of 3 was performed, exploring its potential application as a supramolecular host. The presence of a large number of N‒H H-bond donors allows thermodynamically favourable halide binding in high-energy conformers of 3 which ‘wrap’ around the guests. Nonetheless, the large pre-organisation cost compares unfavourably to the rigid macrocyclic host 2. The nature of non-covalent interactions in host‒guest complexes of 2 and 3 was examined computationally, offering insight into the effective design of future main-group supramolecular receptors.
The adsorption of carbon monoxide (CO) on pristine and group 8B transition metal (TM = Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, and Pt)–doped boron nitride nanocages (BNNCs) was investigated using density functional theory. Structural, energetic, and electronic analyses reveal that TM doping markedly enhances the adsorption capability of BNNCs toward CO, whereas pristine BNNC interacts weakly with the gas molecule. B–site substitution is found to be energetically more favorable than N–site substitution. Among the investigated systems, Ir–doped BNNC exhibits the strongest CO adsorption, highlighting its suitability for CO storage applications. Moreover, significant modulation of the electronic properties is observed upon CO adsorption, with Fe–doped BNNC displaying the largest energy-gap variation and sensitivity, suggesting its potential for CO sensing applications. Overall, TM–doped BNNCs emerge as promising nanomaterials for CO storage and sensing applications.
Incineration is an effective approach to achieve energy recovery and resource utilization of kitchen waste. The potassium ion (K+) abundant in kitchen waste can influence the formation of NOx precursors and subsequently affect nitrogen oxide emissions during the incineration process. However, the detailed catalytic mechanism of K+ remains unclear. In this study, glutarimide and 2-pyrrolidone are used as nitrogen-containing model compounds of kitchen waste, and the catalytic mechanism of K⁺ on the formation of NOx precursors during pyrolysis is systematically investigated based on density functional theory (DFT) calculations. The results indicate that K+ increases the energy barriers of most initial ring-opening reactions, enhancing the pyrolysis stability of glutarimide and 2-pyrrolidone. K+ exhibits a selective catalytic effect on the formation of NH3: it promotes the formation of NH3 from glutarimide but inhibits the formation of NH3 from the pyrolysis of 2-pyrrolidone. Additionally, K+ generally raises the energy barriers of the HCN and HNCO formation paths, thereby inhibiting their generation in most reaction pathways. In most cases, K+ hinders the formation of N-H bond or the conversion of C = N bond to C ≡ N bond by forming a temporary bond with N atom, thus inhibiting the formation of NOx precursors. Additionally, the effect of K⁺ on the decomposition of HNCO into NH3 and HCN is investigated for the first time in this work. The result shows that the presence of K+ promotes the decomposition of HNCO. Overall, this work provides molecular-level insights into the complex catalytic effects of K+ on NOx precursor evolution during kitchen waste pyrolysis, demonstrating that the influence of K+ is highly dependent on the nitrogen-containing species and reaction pathways.
Density functional theory (DFT) calculations were performed to investigate the effects of nitro, nitramino, and azido substituents on the electronic structure and initial decomposition behavior of tricyclic oxadiazole derivatives (PA-1, PA-2, and PA-3). Functional-group substitution has a limited influence on the intrinsic tricyclic framework but induces pronounced local electronic redistribution around reactive sites, thereby affecting bond stability, weak interactions, and local reactivity. PA-3 exhibits the strongest surface electrostatic polarization and relatively weak azido-related N–N bonds, whereas PA-2 shows a distinct weak-interaction pattern associated with its additional N–H···N interaction. Comparative NPA, Hirshfeld, and QTAIM charge analyses, together with Fukui-function and dual-descriptor calculations based on Hirshfeld charges, reveal substituent-dependent variations in the electronic characteristics of key reactive sites. All three compounds preferentially undergo intramolecular hydrogen transfer with similar activation free energies (7.44–7.55 kcal·mol⁻¹), whereas subsequent irreversible bond-cleavage pathways show pronounced substituent dependence. PA-3 exhibits the lowest cleavage barrier of 37.32 kcal mol⁻¹, substantially lower than those of PA-1 and PA-2 (> 53 kcal·mol⁻¹). These results demonstrate that functional-group substitution primarily regulates local electronic structure and the accessibility of competing initial decomposition pathways, providing molecular-level insights into the design of thermally stable tricyclic oxadiazole energetic materials.
Regioselective cross-coupling reactions were performed using benzoylquinolines and cobalt(II) salts as catalysts, as well as manganese(III) acetate as an oxidant. Products of C–C (with 2-phenylpyridine), C–N (with morpholine) and C–P (with diphenylphosphine oxide) coupling were obtained and characterized using X-ray diffraction analysis, cyclic voltammetry, 1H NMR, 13C NMR spectroscopy, and ESI–MS. The electrochemical studies of benzoylquinolines and their products revealed the reaction pathways and factors affecting product yields. The cobalt catalyst directs the reaction to the ortho position of the phenyl ring in benzoylquinoline when coupled with morpholine or 2-phenylpyridine. Diphenylphosphine oxide, on the other hand, is active at the position 5 of the quinoline ring.
The present study reports a comprehensive computational investigation of the electronic structure, optical absorption, charge-transfer (CT) character, aromaticity, and nonlinear optical (NLO) properties of C₁₀H₁₀ (a non-alternant polycyclic hydrocarbon, CP) and its radical derivatives bearing halogen (F, Cl) and alkali metal (Li, Na) substituents. All calculations are performed at the B3LYP level of theory using density functional theory (DFT) and time-dependent DFT (TD-DFT). Energy decomposition analysis (EDA) via the XEDA package reveals systematic trends in electrostatic, exchange, repulsion, and polarization energies. UV-Vis spectral simulations demonstrate progressive redshifts from the UV (neutral, 380 nm) into the visible region (Na•, 570 nm) driven by metal-to-ligand charge transfer (MLCT). Transition density matrix (TDM), charge density difference (CDD), localized orbital locator (LOL), hole–electron overlap, and bonding analyses collectively confirm the dominance of CT excitation in alkali metal derivatives. The first hyperpolarizability (βₜₒₜ) of C₁₀H₁₀Na• is estimated at 4280 a.u. (≅ 45× urea), substantially outperforming classic push-pull chromophores such as p-nitroaniline. Aromaticity analyses (NICS, HOMA, MCI) reveal progressive aromatization from F• to Na•, while excitation energies of lowest excited states span 0.26–1.34 eV and the corresponding exciton binding energies range from 4.06 to 5.43 eV. Based on these computed trends, C₁₀H₁₀Na• and C₁₀H₁₀Li• emerge as promising computational leads for second-harmonic generation.
Three arylhydrazone derivatives of thiazolo[3,2-a]pyrimidinones, distinguished by the halogen atom (F, Cl, Br) in the aryl substituent at C5, were synthesized and studied by the X-ray diffraction method. All compounds crystallize as 1:1 solvates with methanol, but exhibit different supramolecular organization. The replacement of the halogen atom in the aryl substituent (from fluorine to bromine) consistently changes the dominant non-covalent interactions in crystals: from π,π-stacking and chalcogen bonding to the reorganization of hydrogen bonds and, finally, to the directed halogen bond Br…N, which allows purposefully manage supramolecular architecture.
The enthalpies of formation of five families of azoles, parent, protonated parent, neutral N-methyl azoles, protonated N-methyl azoles, and N,N-dimethyl quaternary salts from pyrazole to benzotriazole, in all, 82 compounds, have been studied theoretically and compared with all the available data. The energetic aspects cover enthalpies of formation, proton affinities, and gas-phase basicities. The experimental/calculated agreement allows to correct the experimental value of the proton affinity of benzotriazole and to discuss the tautomerism of 1,2,3-triazole. The numerical data were analyzed using simple regression, multiple regression, absence/presence matrices called Free-Wilson, Supervised Machine Learning Algorithms (SMLAs), and neural network models.
The synthesis of chitosan-illite composite and its uranium adsorption properties were investigated. Structural analyses showed that the composite was successfully formed and provided a surface rich in functional groups. Uranium adsorption studies demonstrated that, unlike conventional chitosan-based composites, the composite exhibits adsorption capacity demonstrated a slight dependence on pH, with a gradual enhancement observed as the pH level increased. The maximum adsorption capacity was determined as 0.305 mol kg− 1 according to the Langmuir model. The kinetic behavior of adsorption was shown to follow the Elovich model, with an initial rate of adsorption of 0.0671 mol kg− 1 min− 1. Thermodynamic findings indicated that the adsorption process is spontaneous and endothermic. Experimental and structural analyses indicated that uranium adsorption proceeds through a combination of surface complexation followed by the formation of uranium-rich surface aggregates at higher surface loadings on the chitosan–illite composite. These findings have shown that this synthesized composite forms a stable surface for uranium removal studies and can be used over a wide pH range.
