Density Functional Theory Calculations Research Articles

Dual channel chemosensor for successive detection of environmentally toxic Pd2+ and CN− ions and its application to cancer cell imaging

BackgroundDetecting and neutralizing Pd2+ ions are a significant challenge due to their cytotoxicity, even at low concentrations. To address this issue, various chemosensors have been designed for advanced detection systems, offering simplicity and the potential to differentiate signals from different analytes. Nonetheless, these chemosensors often suffer from limited emission response and complex synthesis procedures. As a result, the tracking and quantification of residual palladium in biological systems and environments remain challenging tasks, with only a few chemosensing probes available for commercial use. ResultsIn this paper, a straightforward approach for the selective detection of Pd2+ ions is proposed, which involves the design, synthesis, and utilization of a propargylated naphthalene-derived probe (E)-N'-((2-(prop-2-yn-1-yloxy)naphthalen-1-yl)methylene)benzohydrazide (NHP). The NHP probe exhibits sensitive dual-channel colorimetry and fluorescence Pd2+ detection over other tested metal ions. The detection process is performed through a catalytic depropargylation reaction, followed by an excited state intramolecular proton transfer (ESIPT) process, the detection limit is as low as 11.58 × 10−7 M under mild conditions. Interestingly, the resultant chemodosimeter adduct (E)-N'-((2-hydroxynaphthalen-1-yl)methylene)benzohydrazide (NHH) was employed for the consecutive detection of CN− ions, exhibiting an impressive detection limit of 31.79 × 10−8 M. Validation of both detection processes was achieved through 1H nuclear magnetic resonance and density functional theory calculations. For real-time applications of the NHP and NHH probes, smartphone-assisted detection, and intracellular detection of Pd2+ and CN− ions within HeLa cells were studied. SignificanceThis research presents a novel naphthalene derivative for visually detecting environmentally toxic Pd2+ and CN− ions. The synthesized probe selectively binds to Pd2+, forming a chemodosimeter. It successfully detects CN− ions through colorimetry and fluorimetry, offering a low detection limit and quick response. Notably, it's the first naphthalene-based small molecule to serve as a dual probe for toxic analytes - palladium and cyanide. Moreover, it effectively detects Pd2+ and CN− intracellularly in cancer cells.

Construction of Heterostructured NiS/NiSe2 and their application in electrocatalytic water splitting

Development of non-precious metal electrocatalyst that can efficiently catalyze the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) simultaneously, is a great challenge. Herein, density functional theory (DFT) calculations are first conducted to explore the beneficial effect of NiSe2/NiS heterostructure on OER. Based on this, a series of nickel selenosulfides constructed by different amounts of NiS and NiSe2 are synthesized. Results indicate that Ni4–Se2–S2 with the NiS to NiSe2 ratio of 5.82/2.47 displays outstanding electrocatalytic activity for OER/HER, with overpotentials of 228 mV and 155 mV at 10 mA cm−2, respectively. Moreover, a two-electrode electrolyzer using Ni4–Se2–S2 as the anode and cathode exhibits a lower voltage than RuO2||Pt/C. Moderate ratio of NiS to NiSe2 achieves a balance between conductivity and surface area, which endows Ni4–Se2–S2 the best catalytic performances. Our results pave a way for the optimization of heterostructured catalysts.

Highly coordinated Ni-N5 sites for efficient electrocatalytic CO2 reduction toward CO with faradaic efficiency exceeding 99%

Electrochemical production of high value-added CO from CO2 on transition metal-nitrogen-carbon (M−N−C) catalysts is a promising approach to achieve carbon neutral economy, yet the quest for robust catalysts is driven by achieving > 96 % CO faradaic efficiency (FE) under low overpotential and wide potential range. Herein, we report a novel synthetic approach involving post-metallization of the pre-synthesized N-doped carbon (NC-T) support for the fabrication of robust and efficient Ni@NC-T quasi-molecular catalysts toward CO2 electroreduction reaction (CO2RR). The optimum Ni@NC-1100 catalyst exhibited an extremely high FECO > 99 % at −0.72 V vs. reversible hydrogen electrode (RHE). Of interest is the FECO maintained above 96 % over a wide potential window from −0.52 V to −1.12 V. Density functional theory (DFT) calculation validated that the presence of axial pyrrolic-N significantly enhances the Ni-N5 active site for CO2 activation, resulting in the lowest activation energy for the *COOH intermediate generation compared to other axial ligands.

Spectrophotometric and DFT study of Germanium(IV) interaction with 6,7-dihydroxy-2,4-diphenyl-1-benzopyran-1-ium bromide in solutions: Room-temperature cloud point extraction and its analytical application

In the current study, a novel and fast procedure for room-temperature cloud point extraction of Germanium (VI) followed by spectrophotometric detection is developed. A 6,7-dihydroxy-2,4-diphenyl-1-benzopyran-1-ium bromide (DPBP) reagent was proposed for binding Ge (IV) into the extractable colored complex. The interaction of Ge (IV) with the reagent DPBP was studied using spectrophotometry and density functional theory (DFT) calculations. It was established that the complex stoichiometry is 1:2. It was shown that with the increase of the charge of the resulting complex, the Gibbs free energy of the complex formation increases considerably. This means that the formation of neutral species with cis- location of the hydroxyl ligands is the most preferable process. The cloud point phenomenon at room temperature was immediately initiated via ammonium benzoate. The calibration plot for Ge (IV) was obtained in the concentration range of 4–490 μg L−1 under optimized conditions: pH = 1, concentration of DPBP 1.8–2∙10-5 mol/L, 0.12 mol/L aqueous ammonium benzoate and 1 % (v/v) Triton X-100). The limit of detection is 1.2 μg L−1. The method was successfully applied to the determination of Ge(IV) traces in vegetable and rock samples.

Nox impact on mercury removal based on TAC: A comprehensive DFT and XAFS analysis

Nox impact on mercury removal based on TAC: A comprehensive DFT and XAFS analysis

The mechanism and origins of the chemo- and regio-selectivity of ruthenium porphyrin catalyzed C[sbnd]H bonds oxidation

Selective functionalization of polymers derived from branched alkane monomers is extremely challenging due to the low reactivity of CH bonds and uncontrolled depolymerization. In this work, the chemoselective and regioselective catalytic oxygenation mechanism of hydrocarbons with ruthenium porphyrin complexes and aromatic N-oxides was investigated by density functional theory (DFT) calculations. The results revealed that the oxoruthenium porphyrin species with remarkable reactivity as oxygen transfer agents is responsible for the hydrogen abstraction from CH bonds followed by fast hydroxyl radical rebound. Details regarding the calculations of various oxidation processes show that the regioselectivity is related to the intrinsic strength of different CH bonds in branched alkanes and the charge transfer of the hydrogen atom transfer (HAT) step. Comparing the oxidations of branched alkanes to alcohols and ketones, the chemoselectivity is attributed to the relative barriers of HAT pathways in the two-step oxidation stage. Finally, the substituent effects of fluorine in the porphyrin ligand are elucidated and a stronger electron-withdrawing group is predicted to promote the HAT process and regulate hydroxyl radical rebound, ultimately enabling more efficient oxidation. These findings provide relevant information for understanding the selective oxidation of polyolefins through transition metal catalysis and enzymatic catalysis.

Ultrafast and nanomolar detection of Al3+: Furazan based fluorescent chemosensor and its practices in Smartphone, test kit, water samples and living–cell

A new fluorescent chemoprobe (SDAF) was successfully synthesized and utilized as a sensor for the recognition of Al3+ in EtOH:HEPES (3:2, v:v, pH: 7.0) media. The SDAF depicted a selective “turn–on” response at λem = 467 nm to Al3+ over competitive cations, and the SDAF–Al3+ complex had a reversible response with F−. The limit of detection (LOD) was found about at nano–molar level (28.0 nM), demonstrating the sensitivity of the chemoprobe toward Al3+. The binding stoichiometry of SDAF–Al3+ was investigated by TOF–MS, Job's plot, 1H NMR and 13C NMR methods and found as 1:1. The recognition mechanisms of SDAF for the detection of Al3+ were the –C = N isomerization and photoinduced electron transfer (PET) mechanisms, and they were confirmed by density functional theory (DFT) computation. Furthermore, the SDAF was successfully employed in living–cell bioimaging and cytotoxicity, it was also utilized in Smartphone, test–kit and natural spring water (recovery values; 89.01 %– 96.33 %)applications.

Diverse crystalline protein scaffolds through metal-dependent polymorphism.

As protein crystals are increasingly finding diverse applications as scaffolds, controlled crystal polymorphism presents a facile strategy to form crystalline assemblies with controllable porosity with minimal to no protein engineering. Polymorphs of consensus tetratricopeptide repeat proteins with varying porosity were obtained through co-crystallization with metal salts, exploiting the innate metal ion geometric requirements. A single structurally exposed negative amino acid cluster was responsible for metal coordination, despite the abundance of negatively charged residues. Density functional theory calculations showed that while most of the crystals were the most thermodynamically stable assemblies, some were kinetically trapped states. Thus, crystalline porosity diversity is achieved and controlled with metal coordination, opening a new scope in the application of proteins as biocompatible protein-metal-organic frameworks (POFs). In addition, metal-dependent polymorphic crystals allow direct comparison of metal coordination preferences.

Excellent energy storage performance of lead-based antiferroelectric ceramics via enhancing dielectric breakdown mechanism

Lead-based antiferroelectric (AFE) material with high power density has received extensive attention for potential applications in the energy storage devices. Nevertheless, the presence of a secondary phase reduces the band gap and concentrates a significant localized electric field at the center of the tips of both secondary phases, leads to a poor breakdown electric strength (Eb). Hence, we designed high Eb of (Pb1-1.5xSmx)(Zr0.995Ti0.005)O3 ceramics with high energy performance via enhancing dielectric breakdown mechanism by restraining secondary phase. Density functional theory calculations reveal that the valence and conduction bands of secondary phase are in close proximity to the Fermi level, indicating the smaller band gap of secondary phase is unable to withstand the concentration of local electric fields in this samples, thus leading to obtain a poor Eb. UV–vis absorption spectra experiments demonstrate that the overall band gap increases due to the A-site Sm modification strategy, effectively reducing the secondary phase and resulting in elevated levels of Eb. As a consequence, Eb is remarkably improved from 350 kV/cm into 540 kV/cm with increasing Sm3+ content. A record-high Eb of 520 kV/cm and high recoverable energy storage density of 12.9 J/cm3 (energy efficiency of 77.1 %) are achieved in (Pb0.91Sm0.06)(Zr0.995Ti0.005)O3 (PS6ZT) ceramics by tape-casting method. Concerning the performance of pulse charge–discharge, ultrahigh discharge energy density of 8.5 J/cm3 and excellent power density of 188.53 MW/cm3 are achieved in PS6ZT ceramics. Moreover, outstanding stability behavior with a broad frequency range of 1∼140 Hz and a broad temperature range of 20–120 ℃ are obtained. These results show that enhancing Eb mechanism will be provided a potential option to enhanced energy density for PbZrO3-based AFE ceramics.

Fe-N-C single-atom peroxymonosulfate activator based on natural diatomite: dispersion and strengthening mechanism

Iron single atom catalysts were supported on diatomite via Zif-8 precursor and atmosphere induction strategy. The introduction of diatomite makes it possible to regulate the pore structure and active sites of composite catalyst, and the ability of Fe-N-C/diatomite (Fe-N-C/DA) activated peroxymonosulfate (PMS) to degrade bisphenol A (BPA) was 11.8 times and 9.6 times that of pure catalyst and physical mixture. Furthermore, the carbon material forms a composite active center with iron single atoms and achieves efficient PMS activation. The density functional theory calculation results proved that the FeN4 center could grow oxygen-oxygen bond length to enhance PMS self-decomposition. Besides, tetravalent iron, superoxide radicals and singlet oxygen participate in the degradation process of BPA, and the possible degradation pathways of BPA in the Fe-N-C/DA/PMS system were also speculated. Our work provides a sight for the combination of natural minerals and monatomic catalysts to obtain an efficient, stable and potential persulfate activator.

Global machine learning potentials for molecular crystals.

Molecular crystals are difficult to model with accurate first-principles methods due to large unit cells. On the other hand, accurate modeling is required as polymorphs often differ by only 1kJ/mol. Machine learning interatomic potentials promise to provide accuracy of the baseline first-principles methods with a cost lower by orders of magnitude. Using the existing databases of the density functional theory calculations for molecular crystals and molecules, we train global machine learning interatomic potentials, usable for any molecular crystal. We test the performance of the potentials on experimental benchmarks and show that they perform better than classical force fields and, in some cases, are comparable to the density functional theory calculations.

Unlocking a new hydrogen-bonding marker: C-O bond shortening in vicinal diols revealed by rotational spectroscopy.

The conformational space of cis-1,2-cyclohexanediol, a model molecule for cyclic vicinal diols, was investigated using rotational spectroscopy and density functional theory calculations. Four low energy conformers within an energy window of 5 kJ mol-1 were identified computationally. A rotational spectrum of jet-cooled cis-1,2-cyclohexanediol was recorded with a chirped pulse Fourier transform microwave spectrometer. Two sets of rotational transitions were observed and could be assigned to conformers of cis-1,2-cyclohexanediol. The non-observation of other low energy conformers was explained by conformational conversion barrier height calculations and results from experimental spectra recorded with different carrier gases. Eight isotopologues, including those with 13C and 18O, of the lowest energy conformer were observed, allowing the determination of the semi-experimental equilibrium structure, reSE. Interestingly, the structural analysis revealed that the C-O bond length of the intramolecular hydrogen-bond donor is shorter than that of the acceptor. This appears to be a general characteristic of vicinal diols and can be used as a novel hydrogen-bond marker in such compounds.

Ultrafast restricted intramolecular rotation in molecules with aggregation induced emission.

In this work, the ultrafast intramolecular rotation behavior of 1,1,2,3,4,5-hexaphenylsilole has been investigated in several solutions with different viscosities using femtosecond transient absorption spectroscopy combined with density functional theory and time-dependent density functional theory calculations. It is demonstrated that the nonradiative process, which competes with radiative decay, involves two main stages, namely the restricted intramolecular rotation and internal conversion processes. The intramolecular rotation depends on viscosity and presents a significant restriction. The restricted rotational rate is determined to be dozens of picoseconds. The following nonradiative process is strongly dominated by intramolecular rotation. The nonradiative decay rate will decrease with the increase in viscosity, leading to a rise in the radiative probability and photoluminous yield. These results have borne out the mechanism of ultrafast restricted intramolecular rotation of aggregation induced emission and provided a detailed photophysical picture of nonradiative processes.

Confined and spontaneously transformed oxidation structures due to the intrinsic heterogeneous surface morphology of C3N monolayer.

Identifying the oxidation structure of two-dimensional interfaces is crucial to improve surface chemistry and electronic properties. Beyond graphene with only phenyl rings, a novel carbon-nitrogen material, C3N, presents an intrinsic heterogeneous surface morphology where each phenyl ring is encircled by six nitrogen atoms, yet its atomistic oxidation structure remains unclear. Here, combining a series of density functional theory calculations and abinitio molecular dynamics simulations, we demonstrate that thermodynamically favorable oxidation loci are confined to the phenyl ring, and kinetic transformations of oxidation structures are feasible along the phenyl ring, whereas those toward nitrogen atoms are proven to be extremely difficult. These results are attributed to the lower barrier of oxygen atom migration along the phenyl ring, while the significantly high barriers toward nitrogen atoms are due to the heterogeneous potential energy surface for oxygen-C3N interaction. This work highlights the significance of surface morphology on the characteristics of oxidation structure, offering insights into tunable electronic properties via confined interfacial oxidation.

Novel Ferrocenyl‐azole Derivatives: Synthesis, DFT Calculation and Unlocking the Anticancer Potential

Herein, a series of novel ferrocenyl/phenyl/thiophenyl‐azoles was disclosed by vinylic amination of ferrocenyl/phenyl/thiophenyl substituted β‐chloro cinnamaldehydes and acrylonitriles. A highly economical and robust chalcogen‐stabilized iron selenide carbonyl cluster Fe3Se2(CO)9 worked as an efficient catalyst under aerobic conditions. The amination of ferrocenyl/phenyl/thiophenyl substituted β‐chloro‐vinylic Csp2‐Cl with azole derivatives was fully established and fabrication of the Csp2‐N bond was completely supported by various spectral analysis. Moreover, wide range of substrates with functionally different azoles were investigated for the present reaction and good to excellent transformation was recorded. Some of the selected ferrocenated azole derivatives were screened for anti‐cancer activity against the prostate cancer cells (PC‐3) and found to be highly active at low concentration of 5.77µM with IC50 value. Furthermore, HOMO and LUMO levels and energy gap of some selected compounds were calculated by the density functional theory (DFT).

Ferromagnetic Insulating Ground-State Resolved in Mixed Protons and Oxygen Vacancies-Doped La0.67Sr0.33CoO3 Thin Films via Ionic Liquid Gating.

The realization of ferromagnetic insulating ground state is a critical prerequisite for spintronic applications. By applying electric field-controlled ionic liquid gating (ILG) to stoichiometry La0.67Sr0.33CoO3 thin films, the doping of protons (H+) has been achieved for the first time. Furthermore, a hitherto-unreported ferromagnetic insulating phase with a remarkably high Tc up to 180 K has been observed which can be attributed to the doping of H+ and the formation of oxygen vacancies (VO). The chemical formula of the dual-ion migrated film has been identified as La2/3Sr1/3CoO8/3H2/3 based on combined Co L23-edge absorption spectra and configuration interaction cluster calculations, from which we are able to explain the ferromagnetic ground state in terms of the distinct magnetic moment contributions from Co ions with octahedral (Oh) and tetrahedral (Td) symmetries following antiparallel spin alignments. Further density functional theory calculations have been performed to verify the functionality of H+ as the transfer ion and the origin of the novel ferromagnetic insulating ground state. Our results provide a fundamental understanding of the ILG regulation mechanism and shed light on the manipulating of more functionalities in other correlated compounds through dual-ion manipulation.

Molybdate-Templated Luminescent Silver Alkynyl Nanoclusters: Total Structure Determination and Optical Property Analysis.

Two novel MoO42--templated luminescent silver alkynyl nanoclusters with 20-nuclearity ([(MoO42-)@Ag20(C≡CtBu)8(Ph2PO2)7(tfa)2]·(tfa-) (1)) and 18-nuclearity ([(MoO42-)@Ag18(C≡CtBu)8(Ph2PO2)7]·(OH) (2)) (tfa = trifluoroacetate) were synthesized with the green light maximum emissions at 507 and 516 nm, respectively. The nanoclusters were investigated and characterized by single-crystal X-ray crystallography, electrospray ionization mass spectrum (ESI-MS), X-ray photoelectron spectroscopy, thermogravimetry (TG), photoluminescence (PL), ultraviolet-visible (UV-vis) spectroscopy, and density functional theory calculations (DFT). The two nanoclusters differ in their structure by a supplementary [Ag2(tfa)2] organometallic surface motif, which significantly participates in the frontier molecular orbitals of 1, resulting in similar bonding patterns but different optical properties between the two clusters. Indeed, both nanoclusters show strong temperature-dependent photoluminescence properties, which make them potential candidates in the fields of optical devices for further applications.

Do we really need machine learning interatomic potentials for modeling amorphous metal oxides? Case study on amorphous alumina by recycling an existing ab initio database

Abstract In this study, we critically evaluate the performance of various interatomic potentials/force fields against a benchmark ab initio database for bulk amorphous alumina. The interatomic potentials tested in this work include all major fixed charge and variable charge models developed to date for alumina. Additionally, we introduce a novel machine learning interatomic potential constructed using the NequIP framework based on graph neural networks. Our findings reveal that the fixed-charge potential developed by Matsui and coworkers offers the most optimal balance between computational efficiency and agreement with ab initio data for stoichiometric alumina. Such balance cannot be provided by machine learning potentials when comparing performance with Matsui potential on the same computing infrastructure using a single Graphical Processing Unit. For non-stoichiometric alumina, the variable charge potentials, in particular ReaxFF, exhibit an impressive concordance with density functional theory calculations. However, our NequIP potentials trained on a small fraction of the ab initio database easily surpass ReaxFF in terms of both accuracy and computational performance. This is achieved without large overhead in terms of potential fitting and fine-tuning, often associated with the classical potential development process as well as training of standard deep neural network potentials, thus advocating for the use of data-efficient machine learning potentials like NequIP for complex cases of non-stoichiometric amorphous oxides.

C-H Bond Oxidation by MnIV-Oxo Complexes: Hydrogen-Atom Tunneling and Multistate Reactivity.

The reactivity of six MnIV-oxo complexes in C-H bond oxidation has been examined using a combination of kinetic experiments and computational methods. Variable-temperature studies of the oxidation of 9,10-dihydroanthracene (DHA) and ethylbenzene by these MnIV-oxo complexes yielded activation parameters suitable for evaluating electronic structure computations. Complementary kinetic experiments of the oxidation of deuterated DHA provided evidence for hydrogen-atom tunneling in C-H bond oxidation for all MnIV-oxo complexes. These results are in accordance with the Bell model, where tunneling occurs near the top of the transition-state barrier. Density functional theory (DFT) and DLPNO-CCSD(T1) computations were performed for three of the six MnIV-oxo complexes to probe a previously predicted multistate reactivity model. The DFT computations predicted a thermal crossing from the 4B1 ground state to a 4E state along the C-H bond oxidation reaction coordinate. DLPNO-CCSD(T1) calculations further confirm that the 4E transition state offers a lower energy barrier, reinforcing the multistate reactivity model for these complexes. We discuss how this multistate model can be reconciled with recent computations that revealed that the kinetics of C-H bond oxidation by this set of MnIV-oxo complexes can be well-predicted on the basis of the thermodynamic driving force for these reactions.

X-ray absorption and emission spectroscopy of N2S2 Cu(II)/(III) complexes.

This study investigates the influence of ligand charge on transition energies in a series of CuN2S2 complexes based on dithiocarbazate Schiff base ligands using Cu K-edge X-ray absorption spectroscopy (XAS) and Kβ valence-to-core (VtC) X-ray emission spectroscopy (XES). By comparing the formally Cu(II) complexes [CuII(HL1)] (HL12- = dimethyl pentane-2,4-diylidenebis[carbonodithiohydrazonate]) and [CuII(HL2)] (HL22- = dibenzyl pentane-2,4-diylidenebis[carbonodithiohydrazonate]) and the formally Cu(III) complex [CuIII(L2)], distinct changes in transition energies are observed, primarily attributed to the metal oxidation state. Density functional theory (DFT) calculations demonstrate how an increased negative charge on the deprotonated L23- ligand stabilizes the Cu(III) center through enhanced charge donation, modulating the core transition energies. Overall, significant shifts to higher energies are noted upon metal oxidation, emphasizing the importance of scrutinizing ligand structure in XAS/VtC XES analysis. The data further support the redox-innocent role of the Schiff base ligands and underscore the criticality of ligand protonation levels in future spectroscopic studies, particularly for catalytic intermediates. The combined XAS-VtC XES methodology validates the Cu(III) oxidation state assignment while offering insights into ligand protonation effects on core-level spectroscopic transitions.