Iron Center Research Articles

Role of Alkylated 2,6‐bis(tetrazol‐5‐yl)pyridyl Ligands and Iron(II) Salts in Selecting Spin Crossover Complexes

AbstractThe substituents in 2,6‐bis(2‐R‐2H‐tetrazol‐5‐yl)pyridyl neutral ligands R2btp (R=Me, tBu) revealed a prominent effect when reacting with iron(II) salts, in combination with the nature of the anion. According to metal:ligand molar ratio, reaction of R2btp with FeCl2 led to isolate [FeII(R2btp‐κ3N,N’,N”)2](FeIIICl4)2, R=Me (1 a) and tBu (2 a), where the octahedral iron(II) centres bring two tridentate ligands in mer coordination mode, but also [FeII(tBu2btp‐κ3N,N’,N”)(tBu2btp‐κN)2(H2O‐κO)](FeIIICl4)2 (2 b), where one ligand is tridentate, while the other two coordinate the iron(II) through one tetrazolyl nitrogen atom, and the octahedral sphere is completed by one water molecule. In all cases, half of the iron ions are oxidised to iron(III) forming the paramagnetic tetrachloroferrato counterions. Reaction of tBu2btp with Fe(ClO4)2 ⋅ 6H2O led to the octahedral [FeII(tBu2btp‐κ3N,N’,N”)2](ClO4)2 ⋅ 4DCM (4 a ⋅ 4DCM), which shows solvent‐dependent spin crossover behaviour: while 4 a ⋅ 4DCM is blocked in the high spin state, its unsolvated form, 4 a, undergoes spin transition to low spin in two subsequent steps at 206 K, with opening of a 23‐K hysteresis (T1/2↓=194 K, T1/2↑=217 K), and at 136 K (T1/2↓=135 K, T1/2↑=137 K). The magnetic profile changes to an incomplete spin transition when the sample absorbs water molecules yielding 4 a ⋅ 1.5H2O.

Synthesis, Properties, and Electrochemistry of bis(iminophosphorane)pyridine Iron(II) Pincer Complexes

Iron derivatives have emerged as valuable catalysts for a variety of transformations, as well as for biological and photophysical applications, and iminophosphorane can be considered an ideal ligand scaffold for modulating electronic and steric parameters in transition metal complexes. In this report, we aimed to synthesize dichloride and dibromide iron(II) complexes supported by symmetric bis(iminophosphorane)pyridine ligands, starting from readily available ferrous halides. The ease of synthesis of this class of ligands served to access several derivatives with distinct electronic and steric properties imparted by the phosphine moiety. The ligands and the resulting iron(II) complexes were characterized by 31P and 1H NMR spectroscopy and DART or ESI mass spectrometry. While none of these iron(II) complexes could be characterized by single-crystal X-ray diffraction, suitable crystals of a µ-O bridged dinuclear iron complex bearing an iminophosphorane ligand were obtained, confirming a κ3 binding motif. The bis(iminophosphorane)pyridine ligands in the obtained iron(II) complexes are labile, as demonstrated by their facile substitution by terpyridine. Cyclic voltammetry studies revealed that the oxidation of bis(iminophosphorane)pyridine iron(II) complexes to iron(III) species is quasi-reversible, suggesting the strong thermodynamic stabilization of the iron(III) center imparted by the σ-donating iminophosphorane ligands.

Molecular Logic Gates Based on Ferrocene-Containing Compounds

Ferrocene has a unique structure, i.e., a central iron atom neatly sandwiched between two cyclopentadienyl rings, which has revolutionized the chemists’ views about how metals bind to organic π-systems. This structural arrangement leads to some fascinating chemical and photophysical properties. The last three decades, there were reports about receptor molecules that could be considered to perform simple logic operations via coupling ionic bonding or more complex molecular-recognition processes with photonic (fluorescence) signals. In these systems, chemical binding (‘input’) results in a change in fluorescence intensity (‘output’) from the receptor. It has been proven that molecules respond to changes in their environment, such as the presence of various ions, neutral species, pHs, temperatures, and viscosities. Since their first realization by de Silva, molecular logic gates have been intensively experimentally studied, with purely theoretical studies being less common. Here, we present the research that has been conducted on Molecular Logic Gates (MLGs) containing ferrocene and their applications. We categorized such systems into three families of MLGs: long-chain molecules (oligomers or polymers) that incorporate ferrocene, medium-sized molecules that incorporate ferrocene, and systems where ferrocene or its derivatives are used as external additives. Furthermore, MLGs including metal cations without the ferrocene moiety are briefly presented, while computational methodologies for an accurate theoretical study of MLG, including metal cations, are suggested. Finally, future perspectives of MLGs containing ferrocene and their applications are also presented.

Differences in birch tar composition are explained by adhesive function in the central European Iron Age.

Birch bark tar is the most widely documented adhesive in prehistoric Europe. More recent periods attest to a diversification in terms of the materials used as adhesives and their application. Some studies have shown that conifer resins and beeswax were added to produce compound adhesives. For the Iron Age, no comparative large-scale studies have been conducted to provide a wider perspective on adhesive technologies. To address this issue, we identify adhesive substances from the Iron Age in north-eastern France. We applied organic residue analysis to 65 samples from 16 archaeological sites. This included residues adhering to ceramics, from vessel surface coatings, repaired ceramics, vessel contents, and adhesive lumps. Our findings show that, even during the Iron Age in north-eastern France, birch bark tar is one of the best-preserved adhesive substances, used for at least 400 years. To a lesser extent, Pinaceae resin and beeswax were also identified. Through statistical analyses, we show that molecular composition differs in samples, correlating with adhesive function. This has implications for our understanding of birch bark tar production, processing and mode of use during the Iron Age in France and beyond.

The reaction of nonacarbonyldiiron with 8‐alkynyloxyquinolines: Alkynyl activation, cyclization via C‐N bond formation, and C‐H bond cleavage

In this work, the reactions of nonacarbonyldiiron with 8‐alkynyloxyquinoline ligands (L1‐L3) and their resultant iron carbonyl complexes (1a, 1b, 2, and 3) are described. The complexes including the ligands were fully characterized by using a variety of spectroscopic techniques. The four complexes were also crystallographically determined. In the reactions, the quinoline N atom underwent cyclization to form a quinolinium skeleton while the C‐H bond of the quinoline at position 2 or the substituted methyl group was cleaved to form Fe‐C bond(s). Meanwhile, the alkynyl triple bond was reduced to a single bond (1a) or double bonds (1b, 2, and 3) to further coordinate the iron in σ‐bonds or η‐bonds. Particularly, pathways of hydrogenation (1a and 2) and/or dehydrogenation (1b and 3) were accompanied by the reactions. Moreover, the oxidation states of the iron centers in these complexes were identified through analyses of their bond formation, FTIR and NMR spectroscopic signals (1H NMR and DEPT‐135) in combination with their diamagnetic nature, that is, iron (0) for 2 and iron (I) for the rest of the diiron complexes.

In situ single iron atom doping on Bi2WO6 monolayers triggers efficient photo-fenton reaction

Developing an efficient photocatalytic system for hydrogen peroxide (H2O2) activation in Fenton-like processes holds significant promise for advancing water purification technologies. However, challenges such as high carrier recombination rates, limited active sites, and suboptimal H2O2 activation efficiency impede optimal performance. Here we show that single-iron-atom dispersed Bi2WO6 monolayers (SIAD-BWOM), designed through a facile hydrothermal approach, can offer abundant active sites for H2O2 activation. The SIAD-BWOM catalyst demonstrates superior photo-Fenton degradation capabilities, particularly for the persistent pesticide dinotefuran (DNF), showcasing its potential in addressing recalcitrant organic pollutants. We reveal that the incorporation of iron atoms in place of tungsten within the electron-rich [WO4]2− layers significantly facilitates electron transfer processes and boosts the Fe(II)/Fe(III) cycle efficiency. Complementary experimental investigations and theoretical analyses further elucidate how the atomically dispersed iron induces lattice strain in the Bi2WO6 monolayer, thereby modulating the d-band center of iron to improve H2O2 adsorption and activation. Our research provides a practical framework for developing advanced photo-Fenton catalysts, which can be used to treat emerging and refractory organic pollutants more effectively.

A redox switch allows binding of Fe(II) and Fe(III) ions in the cyanobacterial iron-binding protein FutA from Prochlorococcus

The marine cyanobacterium Prochlorococcus is a main contributor to global photosynthesis, whilst being limited by iron availability. Cyanobacterial genomes generally encode two different types of FutA iron-binding proteins: periplasmic FutA2 ABC transporter subunits bind Fe(III), while cytosolic FutA1 binds Fe(II). Owing to their small size and their economized genome Prochlorococcus ecotypes typically possess a single futA gene. How the encoded FutA protein might bind different Fe oxidation states was previously unknown. Here, we use structural biology techniques at room temperature to probe the dynamic behavior of FutA. Neutron diffraction confirmed four negatively charged tyrosinates, that together with a neutral water molecule coordinate iron in trigonal bipyramidal geometry. Positioning of the positively charged Arg103 side chain in the second coordination shell yields an overall charge-neutral Fe(III) binding state in structures determined by neutron diffraction and serial femtosecond crystallography. Conventional rotation X-ray crystallography using a home source revealed X-ray-induced photoreduction of the iron center with observation of the Fe(II) binding state; here, an additional positioning of the Arg203 side chain in the second coordination shell maintained an overall charge neutral Fe(II) binding site. Dose series using serial synchrotron crystallography and an XFEL X-ray pump-probe approach capture the transition between Fe(III) and Fe(II) states, revealing how Arg203 operates as a switch to accommodate the different iron oxidation states. This switching ability of the Prochlorococcus FutA protein may reflect ecological adaptation by genome streamlining and loss of specialized FutA proteins.

Mechanism of directed activation of peroxymonosulfate by Fe-N/O unsymmetrical coordination-modulated polarized electric field

Iron-nitrogen co-doped carbon materials as heterogeneous catalysts have attracted much attention in advanced oxidation processes involving peroxymonosulfate (PMS) due to their unique structure and enormous catalytic potential. However, there is limited research on the influence of different coordination structures on the central iron atoms. Through simple pyrolysis, we introduced oxygen atoms into the Fe-N coordination structure, constructing Fe-N/O@C catalysts with Fe-N2O2 coordination structure, and achieved efficient degradation of bisphenol A (BPA). Quenching experiments, electron paramagnetic resonance, and electrochemical analysis indicate that compared to the free radical activation pathway of Fe-N@C, high-valent iron-oxo species (≡Fe(Ⅳ) = O) are the main reactive oxygen species (ROS) in the Fe-N/O@C/PMS system. Meanwhile, we compared the differences in the oxidation states of Fe atoms and electron density in different coordination structures, revealing the formation of high-valent iron-oxo species and the mechanism of interfacial electron transfer. Therefore, this study provides new insights into the design and development of Fe-N co-doped catalysts for resource-efficient and environmentally friendly catalytic oxidation systems.

Exploring the Specific Role of Iron Center in the Catalytic Activity of Human Serum Transferrin: CTAB-Induced Conformational Changes and Sequestration by Mixed Micelles.

Conformational changes play a seminal role in modulating the activity of proteins. This concept becomes all the more relevant in the context of metalloproteins, owing to the formation of specific conformation(s) induced by internal perturbations (like a change in pH, ligand binding, or receptor binding), which may carry out the binding and release of the metal ion/ions from the metal binding center of the protein. Herein, we investigated the conformational changes of an iron-binding protein, monoferric human serum transferrin (Fe-hTF), using several spectroscopic approaches. We could reversibly tune the cetyltrimethylammonium bromide (CTAB)-induced conformation of the protein, exploiting the concept of mixed micelles formed by three sequestrating agents: (3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate) hydrate (CHAPS) and two bile salts, namely, sodium cholate (NaC) and sodium deoxycholate (NaDC). The formation of mixed micelles between CTAB and these reagents (CHAPS/NaC/NaDC) results in the sequestration of CTAB molecules from the protein environment and aids the protein in reattaining its native-like structure. However, the guanidinium hydrochloride-induced denatured Fe-hTF did not acquire its native-like structure using these sequestrating agents, which substantiates the exclusive role of mixed micelles in the present study. Apart from this, we found that the conformation of transferrin (adopted in the presence of CTAB) displays pronounced esterase-like activity toward the para-nitrophenyl acetate (PNPA) substrate as compared to native transferrin. We also outlined the impact of the iron center and amino acids surrounding the iron center on the effective catalytic activity in the CTAB medium. We estimated ∼3 times higher specific catalytic efficiency for the iron-depleted Apo-hTF compared to the fully iron-saturated Fe2-hTF in the presence of CTAB.

The relative performance of gelatin hydrogels doped with nanostructured transition-metal ferrites for chromium (VI) removal: Packed bed column studies and insights into reduction mechanisms

The article comprehends investigations using gelatin hydrogels reinforced with cobalt and nickel ferrites to remove chromium ions. The synthesized ferrite nanoparticles are mesoporous with high surface areas of 132.059 m2/g and 141.792 m2/g. The deposition of chromium ions on the dissected surfaces is more evident from the morphological studies. Supporting evidence from thermal studies showed how the nanofiller encapsulation increased hydrogels' thermal stability. The bed capacity in the packed bed column is 32.48 mg/g and 31.81 mg/g for cobalt ferrite and nickel ferrite nanoparticles entrapped hydrogels, respectively. X-ray Photoelectron spectroscopy findings indicated that the presence of characteristic peaks at 578.68 eV and 591.16 eV is assigned to hexavalent chromium, and the peaks observed at 575.56 and 583.71 eV correspond to the trivalent state of chromium. The electron transfer from the iron centre to chromium (VI) favoured the reduction of chromium (VI) to less toxic chromium (III)

CO2 Reduction by an Iron(I) Porphyrinate System: Effect of Hydrogen Bonding on the Second Coordination Sphere.

Transforming CO2 into valuable materials is an important reaction in catalysis, especially because CO2 concentrations in the atmosphere have been growing steadily due to extensive fossil fuel usage. From an environmental perspective, reduction of CO2 to valuable materials should be catalyzed by an environmentally benign catalyst and avoid the use of heavy transition-metal ions. In this work, we present a computational study into a novel iron(I) porphyrin catalyst for CO2 reduction, namely, with a tetraphenylporphyrin ligand and analogues. In particular, we investigated iron(I) tetraphenylporphyrin with one of the meso-phenyl groups substituted with o-urea, p-urea, or o-2-amide groups. These substituents can provide hydrogen-bonding interactions in the second coordination sphere with bound ligands and assist with proton relay. Furthermore, our studies investigated bicarbonate and phenol as stabilizers and proton donors in the reaction mechanism. Potential energy landscapes for double protonation of iron(I) porphyrinate with bound CO2 are reported. The work shows that the bicarbonate bridges the urea/amide groups to the CO2 and iron center and provides a tight bonding pattern with strong hydrogen-bonding interactions that facilitates easy proton delivery and reduction of CO2. Specifically, bicarbonate provides a low-energy proton shuttle mechanism to form CO and water efficiently. Furthermore, the o-urea group locks bicarbonate and CO2 in a tight orientation and helps with ideal proton transfer, while there is more mobility and lesser stability with an o-amide group in that position instead. Our calculations show that the o-urea group leads to reduction in proton-transfer barriers, in line with experimental observation. We then applied electric-field-effect calculations to estimate the environmental effects on the two proton-transfer steps in the reaction. These calculations describe the perturbations that enhance the driving forces for the proton-transfer steps and have been used to make predictions about how the catalysts can be further engineered for more enhanced CO2 reduction processes.

Photoinduced C−O Bond Formation through C−C Bond Cleavage of Alcohols by Suppressing Alcohol Oxidation

AbstractHerein, we present a photoinduced deconstructive alkoxyamination of alkyl alcohols catalyzed by iron salts. This transformation involves the initiation of alkoxy radicals through chlorine radical‐induced alkoxy radical formation, followed by β‐scission and trapping of the resulting carbon radicals with 2,2,6,6‐tetramethylpiperidin‐1‐yl (TEMPO). This reaction exhibits a broad substrate scope (40 examples), including primary and secondary alcohols that are prone to oxidation by the combination of TEMPO and iron. Mechanistic investigations have revealed that enhanced coordination of the chloride ion with the iron center inhibits the OH oxidation process, thereby enabling the tolerance of primary and secondary alcohols.

Highly effective activation of peroxymonosulfate via oxygen-coordinated single-atom iron for water decontamination

The traditional peroxymonosulfate-based advanced oxidation processes (PMS-AOPs) have been significantly limited by the high inputs of oxidants. Herein, an oxygen-coordinated Fe-based single-atom catalyst (Fe-N2O1/OCN) was developed as an efficient pathway to activate peroxymonosulfate (PMS). This catalyst allows for a sharp decrease in PMS dosage while avoiding the release of additional sulfate ions into the treated water. The PAPO generates bisphenol-A (BPA) radicals and SO4•− species adsorbed onto Fe-N2O1/OCN, triggering a chain reaction for BPA degradation through BPA-initiated PAPO. The excellent performance of this system is attributed to the oxygen-coordinated iron center, which weakens the coordination of PMS on Fe-N2O1 and prevents its pre-activation. Furthermore, this PMS activation pathway demonstrates high anti-interference performance and can be continuously conducted in complex water matrices for 20 days, providing a promising alternative to traditional PMS-AOPs.

Photooxidation driven formation of Fe-Au linked ferrocene-based single-molecule junctions

Metal-metal contacts, though not yet widely realized, may provide exciting opportunities to serve as tunable and functional interfaces in single-molecule devices. One of the simplest components which might facilitate such binding interactions is the ferrocene group. Notably, direct bonds between the ferrocene iron center and metals such as Pd or Co have been demonstrated in molecular complexes comprising coordinating ligands attached to the cyclopentadienyl rings. Here, we demonstrate that ferrocene-based single-molecule devices with Fe-Au interfacial contact geometries form at room temperature in the absence of supporting coordinating ligands. Applying a photoredox reaction, we propose that ferrocene only functions effectively as a contact group when oxidized, binding to gold through a formal Fe3+ center. This observation is further supported by a series of control measurements and density functional theory calculations. Our findings extend the scope of junction contact chemistries beyond those involving main group elements, lay the foundation for light switchable ferrocene-based single-molecule devices, and highlight new potential mechanistic function(s) of unsubstituted ferrocenium groups in synthetic processes.

Azo-Cyanamide Bridged Dinuclear Iron Complexes Exhibiting no Electronic Coupling but Moderate Magnetic Coupling between the two Iron Centers.

To investigate the effect of long-distance organic ligand on electronic coupling between metallic atoms, the mononuclear and dinuclear complexes [Cp(dppe)Fe(apc)] (1), [{Cp(dppe)Fe}2(μ-adpc)] (2), [{CpMe5(dppe)Fe}2(μ-adpc) (3) and their oxidized complexes [Cp(dppe)Fe(apc)][PF6] (1[PF6]), [{Cp(dppe)Fe}2(μ-adpc)][PF6] (2[PF6]2), [{CpMe5(dppe)Fe}2(μ-adpc)][PF6]2 (3[PF6]2) (Cp=1,3-cyclopentadiene, CpMe5=1,2,3,4,5-pentamethylcyclopentadiene, dppe=1,2-bis(diphenylphosphino)ethane), apc-=4-azo(phenylcyanamido)benzene and adpc2-=4,4'-azodi(phenylcyanamido)) were synthesized and characterized by cyclic voltammetry, UV-vis, single-crystal X-ray diffraction and Mössbauer spectra. Electrochemical measurements showed no electronic coupling between the two terminal Fe units, However, the investigation results of the magnetic properties of the two-electron oxidized complexes indicate the presence of moderate antiferromagnetic coupling across 18 Å distance.

Iron Complexes as Potential Carriers of Diffuse Interstellar Bands: The Photodissociation Spectrum of Fe+(H2O) at Optical Wavelengths.

The fullerene ion C60+ is the only carrier of diffuse interstellar bands (DIBs) identified so far. Transition-metal compounds feature electronic transitions in the visible and near-infrared regions, making them potential DIB carriers. Since iron is the most abundant transition metal in the cosmos, we here test this idea with Fe+(H2O). Laboratory spectra were obtained by photodissociation spectroscopy at 80 K. Spectra were modeled with the reflection principle. A high-resolution spectrum of the DIB standard star HD 183143 served as an observational reference. Two broad bands were observed from 4120 to 6800 Å. The 4120-4800 Å band has sharp features emerging from the background, which have the width of DIBs but do not match the band positions of the reference spectrum. Calculations show that the spectrum arises from a d-d transition at the iron center. While no match was found for Fe+(H2O) with known DIBs, the observation of structured bands with line widths typical for DIBs shows that small molecules or molecular ions containing iron are promising candidates for DIB carriers.

Hallstatt Period Rectangular Farmsteads in the Old Bavarian Loess Landscape: The Hascherkeller Site Revisited

Abstract In the occasionally lively debate about the social structure of the Central European Early Iron Age, the Herrenhof as the presumed seat of a high-status farmer now also plays a role. A rectangular farmstead of this type is the famous Hascherkeller site on the northern outskirts of Landshut. The first magnetic prospection ever conducted at such an archaeological structure was carried out here in 1978. The site became widely known for its distinctive complex appearance and the excavations undertaken there between 1978 and 1981 by Peter S. Wells, then assistant curator of European archaeology at the Peabody Museum of Harvard University. After four decades, an opportunity arose to resume excavations in areas not explored at the time and bring them to a conclusion. The most important result of the recent field work, which was completed in 2022, is the stratigraphic disentanglement of the numerous ditches. The loess terrace, most likely, was initially divided by a ditch running across the terrain. This separating landscape feature may have been contemporaneous with the palisaded farmstead on the eastern edge of the study area. Later, the two rectangular ditched enclosures were constructed, probably the eastern one first. In another, more recent phase, they were joined together by connecting ditches to form a larger settlement complex. Already during the investigation, it was revealed that the middle one of the once assumed three rectangular farmsteads had never existed. In addition, about 200 m further to the southwest, a similar double enclosure was discovered. Here, too, two rectangular enclosures were apparently joined by connecting ditches to form a larger settlement area in a more recent phase. About 5 km to the northeast, in the area of the hamlet Holzen not far from Altheim, a group of unconnected rectangular farmsteads dating from the Hallstatt period has recently been magnetically surveyed. These are characterised by a larger number of long, narrow pits indicating former house sites. The following remarks focus on the latest excavation results and the role of the type of habitation known as Herrenhof in the Early Iron Age settlement system.

Convective-core overshooting and the final fate of massive stars

A massive star can explode in powerful supernova (SN) and form a neutron star, but it may also collapse directly into a black hole. Understanding and predicting the final fate of such stars is increasingly important, for instance, in the context of gravitational-wave astronomy. The interior mixing of stars (in general) and convective boundary mixing (in particular) remain some of the largest uncertainties in their evolution. Here, we investigate the influence of convective boundary mixing on the pre-SN structure and explosion properties of massive stars. Using the 1D stellar evolution code MESA, we modeled single, non-rotating stars of solar metallicity, with initial masses of 5 − 70 M⊙ and convective core step-overshooting of 0.05 − 0.50 pressure scale heights. Stars were evolved until the onset of iron core collapse and the pre-SN models were exploded using a parametric, semi-analytic SN code. We used the compactness parameter to describe the interior structure of stars at core collapse and we found a pronounced peak in compactness at carbon-oxygen core masses of MCO ≈ 7 M⊙, along with generally high compactness at MCO ≳ 14 M⊙. Larger convective core overshooting will shift the location of the compactness peak by 1 − 2 M⊙ to higher MCO. These core masses correspond to initial masses of 24 M⊙ (19 M⊙) and ≳40 M⊙ (≳30 M⊙), respectively, in models with the lowest (highest) convective core overshooting parameter. In both high-compactness regimes, stars are found to collapse into black holes. As the luminosity of the pre-supernova progenitor is determined by MCO, we predict black hole formation for progenitors with luminosities of 5.35 ≤ log(L/L⊙)≤5.50 and log(L/L⊙)≥5.80. The luminosity range of black hole formation from stars in the compactness peak is in good agreement with the observed luminosity of the red supergiant star N6946 BH1, which disappeared without a bright supernova, indicating that it had likely collapsed into a black hole. While some of our models in the luminosity range of log(L/L⊙) = 5.1 − 5.5 do indeed collapse to form black holes, this does not fully explain the lack of observed SN IIP progenitors at these luminosities. This case specifically refers to the “missing red supergiant” problem. The amount of convective boundary mixing also affects the wind mass loss of stars, such that the lowest black hole masses are 15 M⊙ and 10 M⊙ in our models, with the lowest and highest convective core overshooting parameter, respectively. The compactness parameter, central specific entropy, and iron core mass describe a qualitatively similar landscape as a function of MCO, and we find that entropy is a particularly good predictor of the neutron-star masses in our models. We find no correlation between the explosion energy, kick velocity, and nickel mass production with the convective core overshooting value, but we do see a tight relation with the compactness parameter. Furthermore, we show how convective core overshooting affects the pre-supernova locations of stars in the Hertzsprung–Russell diagram (HRD) and the plateau luminosity and duration of SN IIP light curves.

The ortho-substituent effect regulating the separation of photogenerated carriers to efficiently photodegrade tetracycline on the surface of FeCo-based MOFs

It is feasible to improve the photodegradation efficiency of organic pollutants by metal-organic frameworks (MOF)-based semiconductors via ligand engineering. In this work, three (Fe/Co)-XBDC-based MOFs were synthesized by introducing different ortho-functional groups X (X = –H, –NO2, –NH2) next to the carboxyl group of the organic ligand (i.e., terephthalic acid). The analysis focused on the influence mechanism of the adjacent functional group effect of the ligand on the physicochemical properties of the material and the actual photodegradation activity of TC. Multiple pieces of evidences suggested that the differences in electron-induced and photocharge-transfer mechanisms of the above ortho functional groups affect the crystal morphology and photocatalytic activity of FeCo-MOF during pyrolysis. Interestingly, (Fe/Co)–NH2BDC exhibited the highest photocatalytic activity under neutral conditions. The results of density functional theory show that the introduction of a strong donor-NH2 group can enhance light absorption and act as an “electron pump” to supply electrons to the iron center, accelerating the separation and efficient transport of photogenerated carriers on the ligand-metal bridge. In conclusion, this study is a proposal for a strategy of structural regulation for the enhancement of the catalytic activity of (Fe/Co)-MOFs in the photodegradation of TC.

D-Orbital steered FeN4 moiety through N, S dual-site adjustation for zinc-air flow battery

The implementation of pristine covalent organic polymer (COP) with well-defined structure as air electrode may spark fresh vitality to rechargeable zinc-air flow batteries (ZAFBs), but it still remains challenges in synergistically regulating their electronic states and structural porosity for the great device performance. Here, we conquer these issues by exploiting N and S co-doped graphene with COP rich in metal–ligand nitrogen to synergistically construct an effective catalyst for oxygen reduction reaction (ORR). Among them, the N and S co-doped sites with high electronegativity properties alter the number of electron occupations in the d orbital of the iron centre and form electron-transfer bridges, thereby boosting the selectivity of the ORR-catalysed four-electron pathway. Meanwhile, the introduction of COP materials aids the formation of pore interstices in the graphene lamellae, which both adequately expose the active sites and facilitate the transport of reactive substances. Benefiting from the synergistic effect, as-prepared catalyst exhibits excellent half-wave potentials (E1/2 = 912 mV) and stability (merely 8.8% drop after a long-term durability test of 50000 s). Further, ZAFBs assembled with the N/SG@COP catalyst demonstrate exceptional power density (163.8 mW cm−2) and continuous charge and discharge for approximately 140 h at 10 mA cm−2, outperforming the noble-metal benchmarks.