Combination Of DFT Calculations Research Articles

Structural and theoretical insights into the influence of thiocyanate ligands on divalent metal complexes with terpyridine derivatives

Four complexes with terpyridine derivative, thiocyanate anion, and selected d-electron metals were studied. The obtained complexes of the formulation [M(ftpy)(SCN)2(CH3OH)]•DMF (M = Mn (1), Co (2), Ni (3)) and [Cu(ftpy)(NCS)2]•H2O (4), where ftpy = 4′‐(furan-2-yl)-2,2′:6′,2′′‐terpyridine, were characterized using FTIR and UV–Vis spectroscopies, magnetic studies, elemental analysis, and single crystal X-ray crystallography. All compounds crystallize in a triclinic crystal system with space group P1¯ and 1–3 are isomorphous and isostructural. The effect of the modification of the terpyridine ligand and the presence of the thiocyanate ligand on the structure has been verified. Interesting dependence was found in the structure of compound 4, where the two thiocyanate ligands are differently coordinated, one via N and the other via S, and the formation of complex dimers connected through hydrogen bonds is observed. The π-stacking interactions and the resulting solid-state architectures of compounds 1–4 were inspected through a combination of DFT calculations, QTAIM, and NCIPlot analyses, and the stability of the complexes was studied by UV–Vis spectroscopy in various solvents.

ON-OFF Switching of Photocatalytic Hydrogen Evolution by Built-in Pt-Nitrogen-Carbon Reticular Heterojunctions.

COF engineering with a built-in, high concentration of defined N-doped sites overcomes the "black-box" drawback of conventional trial-and-error N-doping methods (used in polymeric carbon nitride and graphene), that hamper a directed evolution of functional carbon interfaces based on structure-reactivity guidelines. The cutting-edge challenge is to dissect the many complex and interdependent functions that originate from reticular N-doping, including modification of the material optoelectronics, band alignments, interfacial contacts and co-localization of active-sites, producing a multiple-set of effectors that can all play a role to regulate photocatalysis. Herein, an ON-OFF gated photocatalytic H2 evolution (PHE) is dictated by the Pt-NPyridine-carbon active sites and probed with a dual COF platform, based on stable β-ketoenamine connectivities made of triformylphloroglucinol (Tp) as the acceptor knots and 1,4-diaminonaphtalene (Naph) or 5,8-diaminoisoquinoline (IsoQ) as donors. Our results showcase two novel COF-Naph-Tp and COF-IsoQ-Tp frameworks featuring quasi-identical slip-stacked microporous structure, and similar surface area, band gap, light harvesting envelope up to 700 nm, fluorescence emission profile/lifetime, and PEIS response at the surface/water interface (Rct=16-10±4 KΩ). A divergent behaviour is indeed observed for COF-IsoQ-Tp with record photoelectrochemical outputs (J=-16 μA cm-2, Rt=3 KΩ at 0.40 V vs RHE) and two orders of magnitude higher rate of PHE (11.3 mmol g-1 h-1, λ>400 nm, pH 5) compared to the inactive COF-Naph-Tp analogue. It turns out that PHE is regulated by the isoquinoline residues at the COF pores where emergent Pt-NPyridine-carbon functional heterojunctions are formed upon photo-deposition of Pt nanoparticles as co-catalysts, as probed by combined XPS and DFT calculations evidence. This work sets a key guideline to direct the design of carbon-based materials encoding the installation of metal-nitrogen-carbon active sites within tailored coordination environments enabling the catalytic performance.

Single-step conversion of methane-steam to methanol on single-atom Cu1/γ-Al2O3 catalyst prepared via electrostatic anchoring

Direct conversion of methane to methanol in heterogeneous catalysis is of paramount importance but remains a challenging issue in improving catalytic activity and selectivity. Here, we report that Cu single-atom sites anchored on γ-Al2O3 oxides (Cu1/γ-Al2O3) using surface electrostatic adsorption, are highly active (methanol yield of ∼47 mmol/molCu/h) and stable in continuous conversion of methane-steam to methanol at 200 °C, comparable to most of the state-of-the-art Cu-zeolite catalysts. The combined DFT calculation and isotope labeling experiments reveal the methane-to-methanol reaction pathway on Cu single-atom sites and methanol formation is the rate limiting step. The further theoretical study indicates that single Cu atom as active site can preferentially activate methane C-H bond instead of methanol and has larger advantage for highly-selective methanol yield compared with [Cu(II)-OH]+ and [CuOCu]2+ active sites. Our molecular-level findings on Cu1/γ-Al2O3 single-atom catalyst pave the way to prepare better non-zeolite catalysts for methane to methanol.

Schrittweiser Abbau von weißem Phosphor: Experimentelle und computergestützte Studien zum Mechanismus der P4‐Hydrostannylierung

AbstractDie Hydrostannylierung der wichtigen Basischemikalie weißer Phosphor (P4) ermöglicht in einer Eintopf‐Reaktion und sogar auf katalytischem Weg die Synthese nützlicher P1‐Produkte. Bisher ist das mechanistische Verständnis dieser Methode jedoch mangelhaft, was die Nutzung für weitere Reaktionen einschränkt. Mit Hilfe von sterisch anspruchsvollen Zinnhydriden, zeitaufgelösten 31P‐NMR‐Experimenten und DFT‐Rechnungen geben wir nun fundierte Einblicke in den Mechanismus der P4‐Hydrostannylierung und beschreiben die Identifikation und Isolierung bisher unbekannter Reaktionsintermediate. Die Ergebnisse erlauben Rückschlüsse zur Kinetik der Reaktion und liefern praktische Hinweise für zukünftige Arbeiten auf dem Gebiet der P4‐Aktivierung.

Heterogeneous nucleation mechanism of CaS and TiN on spinel combining DFT calculations and experiments

The characteristics of composite inclusions between atomic interfaces has been investigated by combining high-angle annular dark field (HAADF) with first-principles computations. The characteristics of the composite inclusions reveal a core of Ca2Al2O5, with CaS and TiN adhering to its surface. According to mismatch degree theory and SEM characterization, the nucleation rate increases with a decreasing degree of mismatch. Notably, the adhesion work of the Ca2Al2O5/CaS interface is greater than that of the Ca2Al2O5/TiN interface, demonstrating the stronger bond strength of the Ca2Al2O5/CaS interface. The prediction of the lowest interfacial energy shows that a stable interface can form between Ca2Al2O5 and MX. Hence, Ca2Al2O5 can be effectively utilized as a nucleation side for CaS (TiN). The present work provides valuable theoretical and technical information for knowledge-based design and prediction of composite inclusion regulation for structural steels, especially for marine engineering steels.

Computational assessment of the reactivity and anticancer activity of 1,2,3-triazole-thiazolidinones derivatives: An approach combining DFT calculations, molecular dynamics simulations, molecular docking, and ADMET

Cancer is a global health burden with escalating incidence and mortality rates, necessitating the exploration of novel therapeutic strategies. 1,2,3-Triazoles, recognized for their diverse biological activities, have emerged as attractive candidates in drug discovery targeting key proteins associated with various cancers. This study presents the synthesis of a library of 1,2,3-triazole hybrids incorporating thiazolidinone and isoxazoline moieties. The antitumor potential of these compounds was evaluated using both in-silico and in-vitro assays. Structure-activity relationship (SAR) analysis revealed that strategic substitution of the para position of the phenyl ring, particularly with a nitro (NO2) group, is promising to enhance cytotoxic activity. The binding potential of the synthesized compounds with the XIAP BIR2 domain, the specific receptor of caspase-3/7 activators, was explored through molecular docking. The stability of the protein-compound complexes procured from the docking was assessed through molecular dynamics (MD) simulation. The docking study demonstrated that the synthesized compounds had the potential to bind to the target protein. Among the compounds and their stereoisomers, compounds (R)-6d and (S)-6e exhibited a better binding potential to the protein. The MD simulation study revealed that the protein-(R)-6d complex was relatively stable.

Efficient photocatalytic water decontamination over a wide pH range by C and O co-doped carbon nitride with tunable band structure

The metal-free, non-toxic, and highly tunable structure of carbon nitride confers unique advantages in photocatalytic advanced oxidation processes. Regulating the generation of radical and non-radical species during photocatalysis to maintain high degradation efficiency across different water matrices is of great practical significance for the application of carbon nitride. In this study, a C and O co-doped modified carbon nitride (UCN) with a high specific surface area was developed for efficient photodegradation of p-chlorophenol (p-Cl) without exogenous oxidants. Characterizations demonstrated that UCN in higher specific surface area exposed more active sites. Additionally, with rising doping levels, UCN exhibited enhanced light absorption capability and a narrower bandgap, which favored the separation of photogenerated electron-hole pairs. The primary active species were identified as holes, accompanied by the generation of superoxide radicals (·O2–) and singlet oxygen (1O2) depending on the pH value. Under acidic conditions, 1O2 was predominantly generated, whereas ·O2– dominated under alkaline conditions. As a result, the removal efficiency of p-Cl was enhanced under both strongly acidic and alkaline conditions. The pseudo-first-order rate constants for p-Cl removal at pH 3, 7, and 11 were 0.0558, 0.0354, and 0.0443 min−1, respectively. Moreover, combining DFT calculations and LC-MS data, analysis on the intermediate products of p-Cl degradation revealed unique characteristics at different pH values, further proving the flexible tunability and providing insights into the practical application of modified carbon nitride.

Unveiling mechanisms of blocking polysulfides by carbon nanotubes

Lithium-sulfur (Li-S) batteries have been considered as a candidate to overcome the limits of Li-ion batteries. However, the polysulfide shuttle effect in Li-S batteries must be addressed before their practical application. A feasible solution to this problem is to insert a carbon nanotube (CNT) interlayer between the Li-S battery cathode and separator for encapsulating polysulfides. Although many CNT interlayers have been developed, how the CNT interlayer blocks polysulfides is still, to a large extent, unknown. In this paper, combined MD simulations and DFT calculations were used to elucidate the effects of CNT size, interspacing, and functional groups on polysulfide encapsulation. Our findings provide new design guidelines for Li-S battery CNT interlayers to optimize the battery performance.

Chemical Orderings in CuCo Nanoparticles: Topological Modeling Using DFT Calculations.

The orderings of atoms in bimetallic 1.6-2.1 nm-large CuCo nanoparticles, important as catalytic and magnetic materials, were studied using a combination of DFT calculations with a topological approach. The structure and magnetism of Cu50Co151, Cu101Co100, Cu151Co50, and Cu303Co102 nanoparticles; their resistance to disintegrating into separate Cu and Co species; as well as the exposed surface sites, were quantified and analyzed, showing a clear preference for Cu atoms to occupy surface positions while the Co atoms tended to form a compact cluster in the interior of the nanoparticles. The surface segregation of Co atoms that are encapsulated by less-active Cu atoms, induced by the adsorption of CO molecules, was already enabled at a low coverage of adsorbed CO, providing the energy required to displace the entire compact Co species inside the Cu matrices due to a notable adsorption preference of CO for the Co sites over the Cu ones. The calculated adsorption energies and vibrational frequencies of adsorbed CO should be helpful indicators for experimentally monitoring the nature of the surface sites of CuCo nanoparticles, especially in the case of active Co surface sites emerging in the presence of CO.

Ammonia monooxygenase-mediated cometabolic biotransformation of volatile 4-chlorophenol in nitrifying counter-diffused biofilms: A combined molecular dynamics simulation, DFT calculation and experimental study

Ammonia monooxygenase (AMO)-mediated cometabolism of organic pollutants has been widely observed in biological nitrogen removal process. However, its molecular mechanism remains unclear, hindering its practical application. Furthermore, conventional nitrification systems encounter significant challenges such as air pollution and the loss of ammonia-oxidizing bacteria, when dealing with wastewater containing volatile organic pollutants. This study developed a nitrifying membrane-aerated biofilm reactor (MABR) to enhance the biodegradation of volatile 4-chlorophenol (4-CP). Results showed that 4-CP was primarily removed via Nitrosomonas nitrosa-mediated cometabolism in the presence of NH4+-N, supported by the increased nicotinamide adenine dinucleotide (NADH) and adenosine triphosphate (ATP) content, AMO activity and the related genes abundance. Hydroquinone, detected for the first time and produced via oxidative dechlorination, as well as 4-chlorocatechol was primary transformation products of 4-CP. Nitrosomonas nitrosa AMO structural model was constructed for the first time using homology modeling. Molecular dynamics simulation suggested that the ortho-carbon in the benzene ring of 4-CP was more prone to metabolismcompared to the ipso-carbon. Density functional theory calculation revealed that 4-CP was metabolized by AMO via H-abstraction-OH-rebound reaction, with a significantly higher rebound barrier at the ipso-carbon (16.37 kcal·mol-1) as compared to the ortho-carbon (6.7 kcal·mol-1). This study fills the knowledge gap on the molecular mechanism of AMO-mediated cometabolism of organic pollutants, providing practical and theoretical foundations for improving volatile organic pollutants removal through nitrifying MABR.

Unravelling White Phosphorus: Experimental and Computational Studies Reveal the Mechanisms of P4 Hydrostannylation.

The hydrostannylation of white phosphorus (P4) allows this crucial industrial precursor to be easily transformed into useful P1 products via direct, 'one pot' (or even catalytic) procedures. However, a thorough mechanistic understanding of this transformation has remained elusive, hindering attempts to use this rare example of successful, direct P4 functionalization as a model for further reaction development. Here, we provide a deep and generalizable mechanistic picture for P4 hydrostannylation by combining DFT calculations with in situ 31P NMR reaction monitoring and kinetic trapping of previously unobservable reaction intermediates using bulky tin hydrides. The results offer important insights into both how this reaction proceeds and why it is successful and provide implicit guidelines for future research in the field of P4 activation.

Rationalization of a Streptavidin Based Enantioselective Artificial Suzukiase: An Integrative Computational Approach.

An Artificial Metalloenzyme (ArM) built employing the streptavidin-biotin technology has been used for the enantioselective synthesis of binaphthyls by means of asymmetric Suzuki-Miyaura cross-coupling reactions. Despite its success, it remains a challenge to understand how the length of the biotin cofactors or the introduction of mutations to streptavidin leads the preferential synthesis of one atropisomer over the other. In this study, we apply an integrated computational modeling approach, including DFT calculations, protein-ligand dockings and molecular dynamics to rationalize the impact of mutations and length of the biotion cofactor on the enantioselectivities of the biaryl product. The results unravel that the enantiomeric differences found experimentally can be rationalized by the disposition of the first intermediate, coming from the oxidative addition step, and the entrance of the second substrate. The work also showcases the difficulties facing to control the enantioselection when engineering ArM to catalyze enantioselective Suzuki-Miyaura couplings and how the combination of DFT calculations, molecular dockings and MD simulations can be used to rationalize artificial metalloenzymes.

Adsorption differences of xanthate, dithiophosphate and dithiocarbamate on stibnite (010) surface with Cu2+ activated: Combined DFT calculations and experiments

Antimony is an important strategic metal resource. Stibnite as one of the main sources of antimony resources, efficiently recycling stibnite has always been a topic of interest. Currently, there is a scarcity of research examining the adsorption differences of butyl xanthate (BX), sodium diethyldithiocarbamate (DDTC) and ammonium dibutyl dithiophosphate (ADD) on the stibnite (010) surface with Cu2+ activated based on atomic scale. This study investigates the adsorption differences of BX, DDTC and ADD on the stibnite (010) surface with Cu2+ activated, combining density functional theory with experiments. DFT calculations showed that there are five adsorption sites of Cu2+ on the stibnite surface, analysis of partial density of states (PDOS) indicated that the difference in hybridization strength between Cu 3d and S 3p orbitals caused discrepancy in adsorption sites performance. Analysis of PDOS, Mulliken population and electron density difference, it can be concluded that the collector interaction strongly with the stibnite surface with Cu2+ activated and the difference of charge transferred by S atoms during the interaction process is the main reason for the differences in adsorption performance and the varying stability of CuS bonds in adsorption models. Under comprehensive comparison the flotation experiments and adsorption tests showed that with Cu2+ activation, the recovery rate of stibnite was significantly improved with DDTC and the adsorption effect was optimal. Finally, the adsorption performance sequence on Cu2+ activated stibnite surface for the three collectors is as follows: DDTC > ADD > BX. This study combining experimental and DFT calculations, provides guidance for the development of efficient collectors for stibnite flotation in the future.

Revealing the interaction forms between Hg(II) and group types (–Cl, –CN, –NH2, –OH, –COOH) in functionalized Poly(pyrrole methane)s for efficient mercury removal

To explore the impact of different functional groups on Hg(II) adsorption, a range of poly(pyrrole methane)s functionalized by –Cl, –CN, –NH2, –OH and –COOH were synthesized and applied to reveal the interaction between different functional groups and mercury ions in water, and the adsorption mechanism was revealed through combined FT-IR, XPS, and DFT calculations. The adsorption performance can be improved to varying degrees by the incorporation of functional groups. Among them, the oxygen-containing functional groups (–OH and –COOH) exhibit stronger affinity for Hg(II) and can increase the adsorption capacity from 180 mg g−1 to more than 1400 mg g−1 at 318 K, with distribution coefficient (Kd) exceeding 105 mL g−1. The variations in the capture and immobilization capabilities of functionalized poly(pyrrole methane)s predominantly stem from the unique interactions between their functional groups and mercury ions. In particular, oxygen-containing –OH and –COOH effectively capture Hg(OH)2 through hydrogen bonding, and further deprotonate to form the –O–Hg–OH and –COO–Hg–OH complexes which are more stable than those obtained from other functionalized groups. Finally, the ecological safety has been fully demonstrated through bactericidal and bacteriostatic experiments to prove the functionalized poly(pyrrole methane)s can be as an environmentally friendly adsorbent for purifying contaminated water.

Enhanced piezo-catalytic performance of BaTiO3 nanorods combining highly exposed active crystalline facets and superior deformation capability: Water purification and activation mechanism

Using piezoelectric materials for advanced oxidation is a green and viable means of water purification and environmental restoration. However, unmodified piezoelectric catalysts exhibited unsatisfactory catalytic performance, which had become a bottleneck for the practical application of piezoelectric catalysis. In this work, piezoelectric responsiveness and exposed active crystal surface area were rationally coordinated by synthesizing one-dimensional BaTiO3 nanorods (BTO NRs). Enhanced piezo-responsivity enables faster free charge carriers transfer, while the highly exposed area of the (001) facets provides more active sites for piezo-catalytic reactions. Consequently, BTO NRs degraded RHB (Rhodamine B) and TC (Tetracycline) with first-order rate constants of 0.018 min−1 and 0.012 min−1, respectively, 5 times higher than BaTiO3 nanoparticles. The specific active sites on the (001) crystal plane were further investigated through a combination of DFT calculations, free radical trapping experiments, and XPS analysis. Ti4+ adsorbs and activates water molecules to generate Ti3+ and •OH, in the catalytic reaction. Afterward, Ti3+ is oxidized to Ti4+ by piezo-holes (holes driven by piezoelectric potential), while •OH is desorbed and involved in the degradation of pollutants. This research not only provides an approach to modify piezoelectric catalysts with high catalytic activity but also presents new insights into the mechanism of piezoelectric catalysis from the viewpoint of the atom level.

Metal-Oxo Electronic Tuning via In Situ CO Decoration for Promoting Methane Conversion to Oxygenates over Single-Atom Catalysts.

Direct methane conversion (DMC) to oxygenates at low temperature is of great value but remains challenging due to the high energy barrier for C-H bond activation. Here, we report that in situ decoration of Pd1-ZSM-5 single atom catalyst (SAC) by CO molecules significantly promoted the DMC reaction, giving the highest turnover frequency of 207 h-1 ever reported at room temperature and ~100 % oxygenates selectivity with H2O2 as oxidant. Combined characterizations and DFT calculations illustrate that the C-atom of CO prefers to coordinate with Pd1, which donates electrons to the Pd1-O active center (L-Pd1-O, L=CO) generated by H2O2 oxidation. The correspondingly improved electron density over Pd-O pair renders a favorable heterolytic dissociation of C-H bond with low energy barrier of 0.48 eV. Applying CO decoration strategy to M1-ZSM-5 (M=Pd, Rh, Ru, Fe) enables improvement of oxygenates productivity by 3.2-11.3 times, highlighting the generalizability of this method in tuning metal-oxo electronic structure of SACs for efficient DMC process.

Metal‐Oxo Electronic Tuning via In Situ CO Decoration for Promoting Methane Conversion to Oxygenates over Single‐Atom Catalysts

AbstractDirect methane conversion (DMC) to oxygenates at low temperature is of great value but remains challenging due to the high energy barrier for C−H bond activation. Here, we report that in situ decoration of Pd1‐ZSM‐5 single atom catalyst (SAC) by CO molecules significantly promoted the DMC reaction, giving the highest turnover frequency of 207 h−1 ever reported at room temperature and ~100 % oxygenates selectivity with H2O2 as oxidant. Combined characterizations and DFT calculations illustrate that the C‐atom of CO prefers to coordinate with Pd1, which donates electrons to the Pd1−O active center (L−Pd1−O, L=CO) generated by H2O2 oxidation. The correspondingly improved electron density over Pd−O pair renders a favorable heterolytic dissociation of C−H bond with low energy barrier of 0.48 eV. Applying CO decoration strategy to M1‐ZSM‐5 (M=Pd, Rh, Ru, Fe) enables improvement of oxygenates productivity by 3.2–11.3 times, highlighting the generalizability of this method in tuning metal‐oxo electronic structure of SACs for efficient DMC process.

The First Example of the Friedel-Crafts Cyclization Leading to (10-Hydroxy-9,10-dihydroanthr-9-yl)phosphonium Salts without the Expected Bradsher Dehydration.

The reaction of (ortho-acetalaryl)arylmethanols with various phosphines PR1R2R3 (R1 = R2 = R3 = Ph; R1 = R2 = Ph, R3 = Me and R1 = R2 = Me, R3 = Ph) under acidic conditions (e.g., HCl, HBF4, TsOH) unexpectedly led to the formation of (10-hydroxy-9,10-dihydroanthr-9-yl)phosphonium salts instead of the corresponding anthryl phosphonium salts. The cyclization occurred according to the Friedel-Crafts mechanism but without the usually observed Bradsher dehydration, giving cyclic products in the form of cis/trans isomers and their conformers. In case of electron-rich and less-hindered dimethylphenylphosphine, all four stereoisomers were recorded in 31P{1H} NMR spectra, while for the other phosphines, only the two most stable cis/trans stereoisomers were detected. This study was supported by DFT and NCI calculations in combination with FT-IR analysis.

Computational screening and experimental fabrication of MoSe2/3d–TMOS heterojunction for room-temperature gas sensor

Heterogeneous engineering is an efficient method to overcome the poor adsorption performance of MoSe2 materials. In this work, the screening process for a suitable transition metal oxide semiconductor with 3d orbital (3d–TMOS) was performed based on the work of adhesion and band edges positions with reference to the MoSe2 material. Then, the gas sensor performance of the suitable composite system was further tested and discussed. The results show that the Cr2O3, Fe2O3 and Co3O4 surface present good interfacial binding strength with MoSe2 compared with other 3d–TMOSs. And the MoSe2/Co3O4 system was selected considering the suitable band edges positions. The as-fabricated MoSe2/0.5–Co3O4 nanocomposite exhibits excellent sensitivity to NO2 at room temperature. Moreover, the MoSe2/0.5–Co3O4 nanocomposite exhibits excellent linear response (R2 = 0.985), selectivity, repeatability, and long–term stability to NO2. The improvement mechanism of gas sensor performance can be mainly attributed to the fast charge extraction rate of type-II heterojunction and greatly sensitive of built-in potential barrier to the carrier density in the MoSe2/0.5–Co3O4 nanocomposite. This research provides a promising method to select the candidates for gas sensor using the combined DFT calculations and experiments.

Highly dense passivation enhanced corrosion resistance of Ti2AlC MAX phase coating in 3.5 wt.% NaCl solution

This study aimed to investigate the dependence of electrochemical behavior upon the microstructural evolution of Ti2AlC MAX phase coating in 3.5 wt.% NaCl solution. The results showed that high-purity Ti2AlC coating with unique equiaxed nanocrystals exhibited remarkably higher impedance and lower current densities compared to those of uncoated Ti-6Al-4V substrate, which was attributed to the formed highly dense and continuously amorphous Al2O3 passive film on the coating surface. According to the combined DFT calculations, both the large diffusivity of Al atoms and the robust stability of Ti2AlxC with Al vacancies exceeding 50% contributed to the unusual achievement of electrochemical passivation characteristics, enabling the significant enhancement of anti-corrosion capability for Ti2AlC coating.