Search Results (310)

Here we perform a detailed information-theoretic (IT) analysis of atomic electron densities in the periodic table, from hydrogen (Z = 1) to lawrencium (Z = 103). By use of the Shannon entropy, the Fisher information and the disequilibrium functionals in both position and momentum spaces as fundamental descriptors of the atomic densities, the periodic table can be represented in a three-dimensional information space as a continuous, highly ordered manifold. The analysis shows that chemical periodicity naturally emerges as a helicoidal manifold (reminiscent of a helix) at the coordinates of a 3D theoretic-information space (Shannon, Fisher, Disequilibrium), with each period forming one segment within the continuous global trajectory. We find information-theoretic signatures of shell structure, sub-shell filling, and electron-configuration anomalies, such as the familiar irregularities seen in chromium and copper. Therefore, the helicoidal character emerges naturally and is not imposed a priori. Further, through the uncertainty principle of the complementary analysis in momentum space, more insights are gained by exposing maximal information-theoretic differentiation for lighter atoms and compression among heavy elements. Notably, momentum-space analysis reveals that hydrogen occupies a natural intermediate position between helium and lithium based on kinetic energy distribution—contrasting with IT position-space results that emphasize hydrogen’s unique delocalized electron density. Indeed, the 3D IT representation of the elements in position space aligns with the view that H does not belong to either the alkali metals or the halogens, but rather stands as a unique, standalone element. This complementary perspective provides new quantitative support for understanding hydrogen’s dual chemical nature, providing new quantitative insight into ongoing debates about hydrogen’s optimal periodic table position. Furthermore, by considering triadic relationships and complexity properties in relation to the López–Mancini–Ruiz (LMC) and Fisher–Shannon (FS) functionals, we show that atomic complexity increases monotonically along with nuclear charge, and we provide a quantitative measure of how organized atomic electron densities are distributed throughout the periodic system. Based on our IT analyses, the fundamental character of periodicity could be addressed by employing helicoidal representations that highlight the characteristics of hydrogen, while simultaneously preserving the autonomy of the blocks of elements. Full article

In this study, first-principles calculations were employed to systematically investigate the adsorption of Cl⁻ on Al₂Cu(110) surfaces, clean Al(111)/Al₂Cu(110) interfaces, and Fe/Si-doped interfaces, as well as the influence of strain on interfacial electronic structure and corrosion activity. When Cl⁻ is adsorbed on Al sites, the bonding between Cl and Al exhibits strong ionic characteristics with localized charge transfer, while adsorption on Cu sites is characterized by more delocalized, covalent interactions. This competition dictates the site-dependent stability of adsorption. Through geometric–electronic synergy, the interface functions as both a “Cl⁻ enrichment zone” and an “activity source,” significantly favoring Cl⁻ adsorption at high-activity anodic sites such as Al-hole and Al-bridge. Conversely, Cu-top sites maintain a high work function and an inert cathodic nature, facilitating the formation of efficient micro-galvanic couples across the interface. Moreover, Fe/Si doping further modulates the interfacial electronic landscape: Si serves as an effective strengthening element due to its low substitution energy and high stability, while Fe primarily forms a solid solution on the Al side, potentially introducing galvanic corrosion risks. Stress analysis indicates that tensile strain systematically enhances surface activity by lowering the work function, while compressive strain non-monotonically influences corrosion through a three-stage mechanism involving the “densification–cracking–plastic relaxation” of the passive film. These findings elucidate the atomistic origins of corrosion initiation at Cu–Al composite interfaces and provide a theoretical foundation for enhancing corrosion resistance through alloy design and strain engineering. Full article

Information-theoretic approach (ITA) has emerged as a powerful density-based framework for interpreting molecular structure, stability, and reactivity within density functional theory (DFT). By treating the electron density as a probability distribution, information-theoretic (IT) descriptors provide physically transparent measures of electron delocalization, localization, and density reorganization, offering an alternative to traditional orbital-based interpretations. This review presents a focused account of the theoretical foundations and chemical significance of IT descriptors and highlights their growing role in density-based chemical analysis. Selected applications are discussed to illustrate how these measures successfully rationalize molecular stability, bonding patterns, reactivity trends, and structure–property relationships across diverse chemical systems. The interplay between IT descriptors and conceptual DFT quantities is also examined, emphasizing their complementary nature in chemical reactivity studies. Overall, this review underscores the versatility and predictive capability of information-theoretic functionals of the electron density and their potential to advance a unified, orbital-free framework for understanding chemical behavior. Full article

Suppressing the polysulfide shuttle effect and accelerating the sulfur redox kinetics remain pivotal challenges for advancing the practical viability of lithium–sulfur batteries (LSBs). In this study, an iodine-doped carbon nitride (I-CN) material was synthesized via a one-step annealing strategy and employed as a metal-free sulfur cathode host. Compared to its pristine counterpart, I-CN exhibits a substantially increased specific surface area, which facilitates the homogeneous dispersion of sulfur species. More importantly, the incorporation of iodine atoms disrupts the equilibrium of the electron cloud distribution within the CN framework, leading to enhanced electron delocalization. This electronic modulation not only significantly improves the charge transport properties of carbon nitride but also strengthens the adsorption of lithium polysulfides (LiPS) and promotes Li₂S nucleation, thereby enabling fast and durable sulfur redox reactions. Benefiting from these synergistic effects, the S@I-CN electrode achieves high sulfur utilization, delivering an initial discharge capacity of 1341.9 mAh g⁻¹ at 0.1C. Even at a high current density of 5C, a remarkable reversible capacity of 472.7 mAh g⁻¹ is retained. Notably, the electrode retains 66.2% of its initial capacity after 800 cycles, demonstrating excellent long-term cycling stability. This halogen-based heteroatom doping strategy thus not only enhances the electrochemical performance of carbon nitride materials in LSBs through the rational manipulation of electron delocalization, but also offers a promising direction for the design of novel metal-free electrocatalysts in related energy conversion systems. Full article

This study aims to investigate the relative stability of the diaminodinitroethylene isomers (cis, trans, and gem). To achieve this goal, calculations at several levels of theory were carried out. The B3LYP, PBE0, and CAM-B3LYP functionals, based on density functional theory (DFT), were used. G4 and MP2 calculations were also executed. All calculation methods predicted that the gem isomer is the most stable, while the cis isomer is the least stable. The energy order obtained for the isomers studied was rationalized by analysis of the detected intramolecular hydrogen bonding, electron delocalization, charge distribution, and changes in atomic energies in the structures studied. The origins of the superior stability of the gem isomer are demonstrated and justified. Full article

Interfacial coupling between CoFe₂O₄ (CFO) nanoparticles and oxidatively functionalized multi-walled carbon nanotubes (MWCNTs) enables controlled modulation of structural, optical, and spin dynamic properties in CFO–MWCNT nanocomposites. The solvothermal synthesis promotes nucleation of CFO on –COOH/–OH functional groups, ensuring uniform anchoring along the nanotube surface. X-ray diffraction confirms a cubic spinel phase with lattice expansion from 8.385 Å to 8.410 Å and crystallite growth from 18 nm to 25 nm, reflecting strain transfer and partial nanoparticle coalescence at the carbon interface. The observed bandgap narrowing from 2.72 eV to 2.50 eV, confirmed via Tauc plot analysis, is attributed to localized defect states induced by charge delocalization and orbital hybridization at the interface of the CFO–MWCNT boundary. DC magnetometry reveals a reduction in saturation magnetization from 46 emu/g to 35 emu/g due to diamagnetic dilution and interfacial spin canting, while coercivity decreases from 852 Oe to 841 Oe, indicating modified pinning and domain-wall dynamics associated with exchange-coupled interfaces. Ferromagnetic resonance measurements show a resonance field shift from 3495 G to 3500 G and an increase in the Landé g-factor from 1.97 to 2.00, signifying altered spin–orbit coupling and enhanced local magnetic perturbations. The spin–lattice relaxation time increases from 1.41 ns to 1.59 ns, demonstrating suppressed phonon-mediated relaxation and improved spin coherence across the hybrid network. Spin density rises from 3.72 × 10²² to 4.58 × 10²² spins/g, confirming an increase in unpaired electrons generated by orbital asymmetry at the interface. The anisotropy field and effective magnetocrystalline anisotropy constant exhibit pronounced modulation, evidencing strengthened exchange stiffness and altered Co²⁺/Fe³⁺ superexchange pathways. These results establish CFO-MWCNT nanocomposites as tuneable platforms for spintronic logic elements, high-frequency microwave attenuation, and magneto-optical device architectures. Full article

Advanced oxidation processes using porphyrin-based heterogeneous catalysts hold promise for removing hazardous pollutants from wastewater. Their high visible-light absorption coefficients enable absorption of light from the solar spectrum. Moreover, their conjugated aromatic skeletons and intrinsic electronic properties facilitate the delocalization of photogenerated electrons during photodegradation. Delaying the recombination of photogenerated electron–hole pairs by introducing specific materials increases efficiency, as separated charges have more time to participate in redox reactions, boosting photocatalytic activities. However, applying these photocatalysts for wastewater treatment is challenging owing to facile agglomeration, deactivation, and recovery of the photocatalyst for reuse, which can significantly increase the overall cost. Therefore, new photocatalytic systems comprising porphyrin molecules must be developed. For this purpose, porphyrins can be conjugated to nanomaterials to create hybrid materials with photocatalytic efficiencies superior to those of free-standing starting porphyrins. Various transition metal oxides (TiO₂, ZnO, and Fe₃O₄) nanoparticles, main-group-element oxides (Al₂O₃ and SiO₂) nanoparticles, metal plasmons (silver nanoparticles), carbon-based platforms (graphene, graphene oxide, and g-C₃N₄), and polymer matrices have been used as nanostructured solid supports for the successful fabrication of porphyrin-conjugated hybrid materials. The conjugation of porphyrin molecules to solid supports improves the photocatalytic degradation activity in terms of visible-light conversion ability, recyclability, active porous sites, substrate mobility, separation of photogenerated charge species, recovery for reuse, and chemical stability, along with preventing the generation of secondary pollution. This review discusses the ongoing development of porphyrin-conjugated hybrid nanomaterials for the heterogeneous photocatalytic degradation of organic dyes, pharmaceutical pollutants, heavy metals, pesticides, and human care in water. Several important results and advancements in the field allow for a more efficient wastewater remediation process. Full article

The photophysical properties of a BODIPY derivative with the highly twisted molecular structure of anthracene-fused boron–dipyrromethene (AN-BDP) were studied with steady-state and time-resolved spectroscopic methods. The fused anthryl and the BDP units in AN-BDP units both adopt distorted geometry (with ca. 10° of torsion), and there is large dihedral angle between the two units (ca. 49.7°). Interestingly, the fluorescence quantum yields are highly dependent on the solvent polarity (59~3%, from toluene to acetonitrile), yet the fluorescence emission wavelength does not change in different solvents. Nanosecond transient absorption spectra indicate that the triplet state is long-lived, with an intrinsic triplet state lifetime of 551 μs. Interestingly the severely twisted structure only shows a moderate intersystem crossing (ISC) yield (10%). Femtosecond transient absorption spectra indicate slow ISC (>1.5 ns), which is in agreement with the fluorescence lifetime (2.3 ns). Time-resolved electron paramagnetic resonance (TREPR) spectra show smaller zero-field-splitting D and E tensors as (−71.4 mT, 16.7 mT, respectively) compared to the triplet state of the iodinated native BDP (D = −104.6 mT, E = 22.8 mT), inferring that the triplet-state wave function of the new compound is delocalized over the twisted molecular framework. The theoretical computation indicated a solvent-polarity-dependent energy barrier for the relaxed S₁ state to a conical interaction (CI) of the S₁ and the S₀ state potential curves, which agrees with the weaker fluorescence in polar solvents. Full article

Heteroatom functionalization of graphene is an effective strategy for designing more sustainable lithium-ion battery electrodes, as it can tune both interfacial adhesion and the electronic features of the carbon lattice. In this work, we investigated the interfacial compatibility between three graphene sheets—pristine graphene, graphene doped with one nitrogen atom (Graphene–N), and graphene doped with one sulfur atom (Graphene–S)—and three lignocellulosic binders (carboxymethylcellulose (CMC); coniferyl alcohol (LcnA); and sinapyl alcohol (LsiA)) using density functional theory (DFT). Geometries were optimized using CAM-B3LYP and M06-2X in combination with the LANL2DZ basis set, while ωB97X-D/LANL2DZ was employed for dispersion-consistent single-point refinements. The computed adsorption energies indicate that all binder–surface combinations are thermodynamically favorable within the present finite-model framework (ΔE_int ≈ −22.6 to −31.1 kcal·mol⁻¹), with LSiA consistently showing the strongest stabilization across surfaces. Nitrogen doping produces a modest but systematic strengthening of adsorption relative to pristine graphene for all binders and is accompanied by electronic signatures consistent with localized donor/basic sites while preserving the delocalized π framework. In contrast, sulfur doping yields a more binder-dependent response: it maintains strong stabilization for LSiA but weakens LCnA relative to pristine/N-doped sheets, consistent with an S-induced local distortion/polarizability pattern that can alter optimal π–π registry depending on the adsorption geometry. A combined interpretation of adsorption energies, electronic descriptors (including ΔE_gap as a model-dependent HOMO–LUMO separation), and topological analyses (AIM, ELF, LOL, and MEP) supports that Graphene–N provides the best overall balance between electronic continuity and chemically active interfacial sites, whereas Graphene–S can enhance localized anchoring but introduces more heterogeneous, lone-pair–dominated domains that may partially perturb electronic connectivity. Full article

Copper(II) coordination complexes with coumarin-derived heterocyclic ligands are promising in inorganic therapeutics for anticancer and antimicrobial applications. To establish quantitative structure–activity relationships for lead design, we studied six copper(II) complexes (Cu1–Cu6)with four- and five-coordinate geometries using Density Functional Theory, Conceptual Density Functional Theory, and visualization analyses. Geometry optimization at M06/6-31G(d)+DZVP revealed distorted coordination environments from $d^9$ Jahn–Teller effects. Tridentate $N_{2}O$-chelatedcomplexes (Cu4–Cu6) showed greater aqueous stability ($\Delta G_{solv}=-43$ to $-50$ kcal·mol⁻¹) than four-coordinate analogs ($-29$ to $-31$ kcal·mol⁻¹). CDFT global descriptors contrasted reactivity: four-coordinate Cu1–Cu2 had higher electron affinity (>4.2 eV) and electrophilicity (>5.7 eV), suggesting propensity for redox cycling and for undergoing nucleophilic attack by DNA bases, whereas Cu4–Cu6 displayed increased chemical hardness (3.43–3.54 eV) and lower electrophilicity (≈3.8 eV), implying enhanced kinetic stability and bioavailability. Frontier orbital analysis indicated ligand-to-metal charge transfer via a LUMO delocalized over the $\pi$-conjugated coumarin, facilitating intercalation by $\pi$-$\pi$ stacking. The visualization showed strong covalent bonds (blue isosurfaces) stabilizing the metal and dispersive $\pi$ interactions (green surfaces) on the ligand, enabling solvent interactions and biomolecular recognition. Tridentate $N_{2}O$ coordination thus balances electronic stability and biological reactivity, making Cu4–Cu6 promising for further study. Full article

Nitrogen gas is one of the most abundant resources on Earth, serving as a fundamental component in both biological and industrial processes. Nevertheless, this simple molecule can only be activated by a limited group of microorganisms in nature. Significant efforts have been devoted to replicating this biological activity using metalorganic approaches. However, it is becoming increasingly evident that non-covalent interactions, particularly ionic interactions, can further enhance catalytic reactions. In this work, the effect of alkali and alkaline-earth cations on dinitrogen activation was assessed using Density Functional Theory (DFT) at distances ranging from 2 to 10 Å. This analysis revealed three distinct activity regimes. In Case I, the polarization of the N₂ molecule is the primary driving force; in Case II, the polarization effect is less pronounced; and in Case III, electrostatic interactions dominate, enhancing electron delocalization within the N₂–Mⁿ⁺ system. Among the various cations, those belonging to group II-A are particularly noteworthy due to their high ionic potential and polarizing power, with Mg²⁺ standing out for its superior activity at an N₂–Mg²⁺ distance of 2.7 Å. Consequently, these theoretical insights can serve as a guiding strategy for designing efficient N₂-activating complexes that integrate covalent and non-covalent interactions synergistically. Full article

Background/Objectives: The ¹⁰³Pd/^103mRh in vivo generator represents a promising Auger electron-emitting system, in which both parent and daughter radionuclides emit predominantly Auger electrons with minimal accompanying radiation. This study investigates the release dynamics of daughter radionuclides from the ¹⁰³Pd/^103mRh in vivo generator and evaluates the underlying mechanisms governing bond rupture and daughter retention. Methods: Cyclotron irradiation of rhodium foils was performed in two separate batches, followed by radionuclide separation using conventional wet chemistry and a novel dry distillation technique. The purified ¹⁰³Pd radionuclide was used to radiolabel DOTA-TATE, phthalocyanine-TATE, and DOTA-TOC chelators. The resulting complexes were immobilized on Strata-X and Strata-C18 solid-phase extraction columns. Scheduled elution experiments were conducted to quantify the release of the ^103mRh daughter radionuclide. Results: The measured ^103mRh release rates were 9.8 ± 3.0% and 9.6 ± 2.7% from Strata-X columns with DOTA-TATE and phthalocyanine-TATE, respectively, and 10.5 ± 2.7% and 12.0 ± 0.5% from Strata-X and Strata-C18 columns, respectively, with DOTA-TOC. These values are significantly lower than the ~100% release predicted based on the reported Auger electron yield of 186%. One explanation for this difference could be potential inconsistencies in decay data that may require correction; this needs further investigation. The results further demonstrated that delocalized π-electrons, introduced via phthalocyanine-based chelation, did not mitigate daughter release. Conclusions: The low observed daughter nuclide release represents a favorable characteristic for the future clinical translation of the ¹⁰³Pd/^103mRh Auger emitter pair. The findings support the conclusion that Auger electron cascades, rather than nuclear recoil energy, dominate bond rupture processes. Full article

Preeclampsia (PE) affects 2–8% of pregnancies, yet it lacks curative treatment options. Oxidative stress caused by the release of reactive oxygen and nitrogen species (ROS/RNS) in the placenta is common in abnormal placental development. It can cause downstream signaling and the formation of anti-angiogenic factors, e.g., soluble fms-like tyrosine kinase 1 (sFLT-1), leading to symptoms of PE, such as hypertension, proteinuria, and, in severe cases, eclampsia. Mitochondria-targeted antioxidants were developed to reduce oxidative stress and alleviate PE symptoms. Ten organofluorine diaryl hydrazones were designed as potential antioxidants, synthesized, and tested for their activity using the 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), and oxygen radical absorbance capacity (ORAC) assays. Compounds 2, 3, 5, and 6 showed excellent antioxidant capacity in all three assays and were tested in an in vitro human trophoblast cell culture system mimicking PE in which the cells were exposed to oxidative stress inducing the release of sFLT-1. The anti-angiogenic factor sFLT-1 was greatly reduced in cells treated with antioxidants. Compounds 5 and 6 were more effective in preventing sFLT-1 release than 2 and 3. Density functional theory calculations of the electronic structures of compounds 2, 5, and 6 were conducted at the M06-2X/6-311G+(d,p) level to further understand the reactivity profile of these molecules. The electron density of delocalized bonds (EDDB(r)) was calculated to analyze the effect of delocalization on radical stabilization. Full article

Tennantite (Cu₁₂As₄S₁₃) and enargite (Cu₃AsS₄) are two important minerals that simultaneously contain copper and arsenic. Detailed studies of their structure and properties are crucial for understanding their oxidation, flotation, and leaching. This study investigates the crystal structures, electronic properties, and reactivity of these two copper-arsenic minerals from the perspectives of atomic bonding, charge, density of states, and d-orbital splitting. The results indicate that tennantite is a crystal with mixed Cu valence states of +2 and +1 (predominantly +1), while the Cu in enargite is in the +1 state. The valence state of As in tennantite (+3) is lower than that in enargite (+5). Orbital energy level calculations show that the energy gaps between the copper d-orbitals are small in both minerals, indicating strong electron delocalization and, consequently, strong covalent character in the crystals, which is also confirmed by Mulliken bond population calculations. The presence of arsenic is the reason for the enhanced covalency. It is noteworthy that tennantite exhibits stronger covalency. The Cu 3d and As 4p electrons in tennantite are more electronically active than those in enargite. In tennantite, the strong d-electron delocalization caused by d-p hybridization between Cu and S leads to similar 3d electronic properties between 3-coordinated and 4-coordinated Cu. The energies of the five d-orbitals of the 4-coordinated Cu in enargite are lower than those of the 4-coordinated Cu in tennantite, which may affect the ability of Cu 3d electrons to enter the empty orbitals of S atoms in sulfur-containing collectors to form π back-bonding, thereby reducing the collecting ability of enargite. On the other hand, the splitting energy of the 4-coordinated Cu 3d orbitals in enargite is significantly smaller than that in tennantite, making the structure less stable and, thus, potentially more prone to dissolution. Full article

Hydrogen peroxide (H₂O₂) is a key oxidant for green chemical processes, yet its catalytic utilization and activation efficiency remain limited by material instability and uncontrolled radical release. Here, we report a dual-functional, hollow conductive polymer nanostructure that enables selective modulation of H₂O₂ reactivity through interfacial physicochemical design. Hollow polypyrrole nanospheres functionalized with carboxyl groups (PPy@PyCOOH) were synthesized via a one-step Fe²⁺/H₂O₂ oxidative copolymerization route, in which H₂O₂ simultaneously served as oxidant, template, and reactant. The resulting structure exhibits enhanced hydrophilicity, rapid redox degradability (>80% optical loss in 60 min (82.5 ± 4.1%, 95% CI: 82.5 ± 10.2%), 10 mM H₂O₂, pH 6.5), and strong electronic coupling to reactive oxygen intermediates. Subsequent tannic acid–copper (TA–Cu) coordination produced a conformal metal–polyphenol network that introduces a controllable Fenton-like catalytic interface, achieving a 50% increase in ROS yield (1.52 ± 0.08-fold vs. control, 95% CI: 1.52 ± 0.20-fold) while maintaining stable photothermal conversion under repeated NIR cycles. Mechanistic analysis reveals that interfacial TA–Cu complexes regulate charge delocalization and proton–electron transfer at the polymer–solution boundary, balancing redox catalysis with energy dissipation. This work establishes a sustainable platform for H₂O₂-driven redox and photo-thermal coupling, integrating conductive polymer chemistry with eco-friendly catalytic pathways. Full article