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Synthetic manganese catalysts that activate hydrogen peroxide perform a variety of hydrocarbon oxidation reactions. The most commonly proposed mechanism for these catalysts involves the generation of a manganese(III)-hydroperoxo intermediate that decays via heterolytic O–O bond cleavage to generate a Mn(V)-oxo species that initiates substrate oxidation. Due to the paucity of well-defined MnIII-hydroperoxo complexes, MnIII-alkylperoxo complexes are often employed to understand the factors that affect the O–O cleavage reaction. Herein, we examine the decay pathways of the MnIII-alkylperoxo complexes [MnIII(OOtBu)(6Medpaq)]+ and [MnIII(OOtBu)(N4S)]+, which have distinct coordination environments (N5− and N4S−, respectively). Through the use of density functional theory (DFT) calculations and comparisons with published experimental data, we are able to rationalize the differences in the decay pathways of these complexes. For the [MnIII(OOtBu)(N4S)]+ system, O–O homolysis proceeds via a two-state mechanism that involves a crossing from the quintet reactant to a triplet state. A high energy singlet state discourages O–O heterolysis for this complex. In contrast, while quintet–triplet crossing is unfavorable for [MnIII(OOtBu)(6Medpaq)]+, a relatively low-energy single state accounts for the observation of both O–O homolysis and heterolysis products for this complex. The origins of these differences in decay pathways are linked to variations in the electronic structures of the MnIII-alkylperoxo complexes. [ABSTRACT FROM AUTHOR]

Metal oxide catalysts' performance depends on their crystal structure, including the surface arrangement and coordination of metal cations and oxygen anions on the exposed facets. Here, we fabricated Co3O4 nanocrystals (NCs) with predominantly exposed (110), (111), (112), and (114) facets in the shapes of nanorod (Co-R), hexagonal nanoplate (Co-H), nanolaminar (Co-L), and nanoparticle (Co-P), respectively. The Co3O4 NC with exposed (114) high-index facet exhibits the highest 5-hydroxymethylfurfural (HMF) electrocatalytic activity, while the Co3O4 NC with exposed (112) shows the lowest activity. Both density functional theory (DFT) calculations and experiments reveal that the primary factor impacting the catalytic performance of Co3O4 NCs is the difference in HMF adsorption energy on various crystal facets. By doping Cr into Co3O4 (114), we tuned the adsorption energy of HMF to an optimal level, thereby achieving the best catalytic performance. Based on this, the adsorption behavior of other aldehyde–alcohol organic small molecules was also evaluated, and the linear relationship between adsorption strength and catalytic activity was confirmed. This work demonstrates that adjusting the exposed crystal facets of Co3O4 can alter the adsorption and catalytic capabilities of aldehyde–alcohol organic small molecules. It also provides explicit knowledge that could improve our understanding of facet-dependent reactions for other metal oxide catalysts. [ABSTRACT FROM AUTHOR]

For effective overall water splitting (OWS) in alkaline media, a novel Ru-doped bimetal oxide (Ru-NiCo2O4) catalyst deposited onto a conductive nickel foam (NF) is fabricated by a multi-step hydrothermal reaction, ion exchange, and subsequent annealing process. The distinctive 3D nanoneedle-like arrays not only provide an even distribution of Ru decorated NiCo2O4, but also expose additional active sites, facilitating electron transport and improving reaction kinetics. Besides, density functional theory (DFT) studies elucidate the electronic structure regulation in Ru-NiCo2O4 and the modification of the d-band center optimizes H* adsorption energy, which considerably increased the hydrogen production efficiency. Considering the aforementioned advantages, the as-prepared Ru-NiCo2O4 electrocatalyst exhibits greatly improved catalytic activity, requiring only 25 mV and 249 mV at 10 mA cm−2 for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively, as well as robust stability. Amazingly, the Ru-NiCo2O4 electrode in a two-electrode alkaline electrolyzer only needs 1.55 V to produce 10 mA cm−2, making it more efficient than the commercial RuO2‖‖Pt/C electrode (1.62 V). More importantly, 0.33 M urea only needs a low voltage of 1.427 V to drive the urine-mediated electrolysis, which is about 123 mV less than the urea-free electrolysis cell. This work presents an effective electronic structure engineering approach based on heteroatom doping that may be extended to design and fabricate novel high-performance OWS catalysts. [ABSTRACT FROM AUTHOR]

Antibiotic contamination has become one of the most pressing problems in the field of water purification. Using nano-graphite (nano-G) as a carbon carrier, a ZrO2-MnOx/nano-G composite electrode with high catalytic activity was prepared by a hot pressing method based on MnOx/nano-G prepared by a sol--gel method. The results showed that the ZrO2-MnOx/nano-G electrode reduces charge transfer resistance while improving surface oxygen desorption ability. MnOx can catalyze the two-electron reduction of O2 to produce H2O2, which can then be converted to •OH and •O2-. Thereafter, the results of free radical capture experiments confirmed that •O2- played a significant role in the electrocatalytic degradation of tetracycline hydrochloride (TC) by a ZrO2-MnOx/nano-G composite electrode. Furthermore, the abundant hydroxyl groups on the surface of nano-G and ZrO2 particles can be used as active sites for catalyzing the Mn3+/Mn4+ redox reaction, resulting in the generation of additional free radicals. The high-efficiency electrocatalytic degradation of TC was achieved through the synergistic action of the three. Under optimal reaction conditions, the degradation rate of TC reached 93% after 120 min of electrolysis. ZrO2-MnOx/nano-G displayed satisfactory stability following 10 cycles of degradation experiments. Finally, the potential TC degradation pathway was investigated using liquid chromatography-mass spectrometry (LC-MS) and density functional theory (DFT), and the degradation mechanism was clarified. [ABSTRACT FROM AUTHOR]

For the heterogeneous reaction of asymmetric hydroformylation (AHF), a highly decentralized active Rh site played a key role in enhancing the yield of chiral isomeric aldehydes. Herein, the mesoporous Rhloaded catalyst (Rh@MOF-5) was prepared using a zinc-based metal--organic framework (MOF-5) to serve as a carrier. During the AHF reaction, the HRh(BINAP)(CO)2 component was formed by the combination of active Rh in Rh@MOF-5 and (R)-BINAP under a syngas atmosphere (H2/CO = 1). The Rh@MOF-5 showed a higher yield of iso-aldehydes (Yiso = 86.71%) and enantioselectivity (ee = 25.01%) of S-iso-aldehydes, which was attributed to the synergy of BINAP and the highly dispersed active Rh sites. Furthermore, density functional theory (DFT) calculation results show the feasible mechanism of HRh(BINAP)(CO)2 catalyzed with 6 steps, and the Rh--H insertion step determined the type of product. The higher enantioselectivity and regioselectivity of S-iso-aldehydes using this catalyst were due to the lower barrier of the S-iso-aldehyde precursor than other product precursors in the step of Rh--H insertion. [ABSTRACT FROM AUTHOR]

SO2 and NO2 capture and conversion have been investigated via density functional theory (DFT) and grand canonical Monte Carlo (GCMC) simulations using a novel hydrogen-bonded 3D metal--organic framework (MOF) containing a Zn(II) centre and a partially fluorinated (polar -CF3) long-chain dicarboxylate ligand with a melamine (basic -NH2) co-ligand. Initially, computational single-component isotherms have been determined for SO2 and NO2 gases. These simulations have shown exothermic adsorption enthalpies of ~36.4 and ~28.6 kJ mol-1 for SO2 and NO2, respectively. They have also indicated that SO2 has a high affinity for polar -CF3 and basic-NH2 binding sites of the ligand in the framework pore walls. The lower adsorption capacity of NO2 compared with SO2 is due to weaker electrostatic interactions with the framework. Furthermore, MOF adsorbent selectivity for removing trace amounts of SO2 and NO2 in flue gases has been estimated through the co-adsorption of ternary gas mixtures (SO2/ CO2/N2 and NO2/CO2/N2). Together with DFT, the climbing image nudged elastic band (CI-NEB) method has been used for investigating the plausible mechanisms for HbMOF1 catalyzed cycloadditions of SO2 and NO2 with epoxides leading to the formation of cyclic sulphites and nitrates, respectively. [ABSTRACT FROM AUTHOR]

Despite p-block clusters being known for over a century, their application as catalysts to mediate organic transformations is underexplored. Here, the boron functionalized [P7] cluster [(BBN)P7]2- ([1]²-; BBN = 9-borabicyclo[3.3.1]nonane) is applied in the dearomatized reduction of pyridines, as well as the hydroboration of imines and nitriles. These transformations afford amine products, which are important precursors to pharmaceuticals, agrochemicals, and polymers. Catalyst [1]2- has high stability in these reductions: recycling nine times in quinoline hydroboration led to virtually no loss in catalyst performance. The catalyst can also be recycled between two different organic transformations, again with no loss in catalyst competency. The mechanism for pyridine reduction was probed experimentally using variable time normalization analysis, and computationally using density functional theory. This work demonstrates that Zintl clusters can mediate the reduction of nitrogen containing substrates in a transition metal-free manner. [ABSTRACT FROM AUTHOR]

Density functional theory electronic structure calculations were employed to study a proposed novel type of interaction between NH3 and the metallic ring of cyclic trinuclear Ag(I) clusters of the general formula cyclo-Ag3(μ2-L)3 bearing 15 different bridging organic ligands L. Scan single point energy calculations revealed that the most stable orientation of NH3 is that with a N atom facing the center of the silver metallic ring and bridging the three metal centers. Starting with this orientation we performed geometry optimizations of the cyclo-Ag3(μ2-L)3(μ3-NH3) complexes. The optimized geometries retain the initial orientation of NH3. The zero point energy corrected interaction energies, D0, of NH3 with the metallic ring are found in the range 4.2–12.4 kcal mol−1 while the distance of NH3 from the center of the ring is in the range 2.317–2.519 Å, both indicative of a relatively strong interaction. A multitude of theoretical methods employed revealed that the interaction of NH3 with the silver metallic ring is mainly of ionic nature with a contribution of van der Waals forces. Molecular structure–property relationships indicate that the magnitude of D0 increases upon increasing the charge of the silver metal centers and decreasing the LUMO energy of the cyclo-Ag3(μ2-L)3 clusters. [ABSTRACT FROM AUTHOR]

Room-temperature sodium–sulfur (Na–S) batteries hold great potential for next-generation energy storage devices due to their high theoretical energy density and low cost. However, the shuttling effect of sodium polysulfide (Na2Sn) species and the sluggish kinetics of the electrochemical conversion reaction greatly hamper the practical application of Na–S batteries. To address these challenges, by means of density functional theory (DFT) computations, we proposed two-dimensional metal chloride (MCl2, M = Mg and Ni) monolayers as multifunctional anchoring materials, including immobilizing soluble Na2Sn intermediates, boosting the reduction reaction of Na2Sn and the decomposition of Na2S species. Our results revealed that the NiCl2 monolayer can effectively immobilize the higher-order Na2Sn species with a stronger binding strength than the common electrolytes to prevent their dissolution. In particular, the NiCl2 substrate exhibits excellent electrocatalytic activity for the sulfur reduction reaction with a low free energy barrier (0.37 eV) and the Na2S decomposition reaction with a small kinetic barrier (0.45 eV), greatly lowering the energy barriers of Na2Sn conversions during discharge and charge and thus guaranteeing the fast redox kinetics and high sulfur utilization of Na–S batteries. Therefore, we predicted that NiCl2 monolayers can be utilized as a highly efficient multifunctional anchoring material for Na–S batteries. [ABSTRACT FROM AUTHOR]

Investigation of catalytic hydrogenation of CO2 to CO via the reverse water-gas shift (RWGS) was undertaken using Ni/SiO2-based catalysts. Among the array of catalysts tested, the Ni/SiO2 catalyst derived from the reduction of silicalite-1-encapsulated, ligand-protected Ni2+ (Ni0.2@S-1-red) exhibited promising performance. This catalyst demonstrated a CO2 conversion rate approaching the equilibrium conversion of RWGS, a selectivity for CO exceeding 99%, and a high space time yield of CO (9.7 mol gNi -1 h-1). The outcomes observed can be attributed to several factors, such as the highly dispersed Ni0 and Niδ+ species, as well as the presence of bridging oxygen of the Ni-O-Si structure, on which CO2 can be adsorbed moderately. The moderately bonded CO2 on Ni0.2@S-1-red allows for the efficient desorption of its reduced intermediate, i.e. *CO, resulting in the generation of gaseous CO at a rapid rate, consequently preventing its deep hydrogenation to CH4. Complementary Density Functional Theory (DFT) calculations were performed and revealed that CO molecules have poor adsorption and higher adsorption energy on the Ni@S-1 surface compared to the S-1 surface. This supports the rapid desorption of *CO and the observed high selectivity of CO. Moreover, the structure-activity correlation analysis further supports the claim of Ni0.2@S-1-red as a promising RWGS catalyst. [ABSTRACT FROM AUTHOR]

The electronic structure, changes in aromatic behavior, and stability of the m-quinone, the least studied member of the benzoquinone family, have been analyzed. Through unrestricted density functional theory calculations, three aromaticity criteria (magnetic, electronic, and geometric), and resonance forms through the valence bond model, we have sought to answer why this isomer prefers the triplet state in its ground state. The answer is given in terms of spin density delocalization and proposed resonance structure contributions. The triplet state presents a higher spin delocalization which can be observed in the condensed values and the higher number of resonance forms contributing to the delocalization. Additionally, using magnetic criteria, we have used a simple but effective model to quantify the contribution of the proposed resonance structures, which have an excellent agreement with the spin density values. [ABSTRACT FROM AUTHOR]

3-Imidazo[1,2-α]pyridine coumarin molecules 3a–3d with four different substituents were synthesised from salicylic aldehyde derivatives, ethyl acetoacetate and 2-aminopyridine derivatives, and exhibited strong blue fluorescence in non-polar solutions and large Stokes shift (184–210 nm) in polar solutions. All these were validated using density functional theory (DFT) and time-dependent density functional theory (TD-DFT). Furthermore, 3a-3d exhibited a solvatochromism effect and solid state fluorescence. The results indicated that the introduction of the 3-imidazo[1,2-α]pyridine group at the 3 positions of coumarin constructed an asymmetric electronic structure, which induced intramolecular charge transfer (ICT) with non-radiative energy enhancement, leading to large Stokes shifts. Meanwhile, by introducing an electron-donating group into imidazo[1,2-α]pyridine, the HOMO (highest occupied molecular orbital)–LUMO (lowest unoccupied molecular orbital) gap can be narrowed to enhance ICT, further increasing the Stokes shift, suggesting a promising and novel model for achieving large Stokes shifts for the development of coumarin dyes. [ABSTRACT FROM AUTHOR]

Photoinduced electron-separation and -transport processes are two independent crucial factors for determining the efficiency of photocatalytic hydrogen production. Herein, a sulfur vacancy defect-decorated CoSx@In2S3 (CoSx@VS-In2S3) core/shell heterojunction photocatalyst was synthesized via an in situ sulfidation method followed by a liquid-phase corrosion process. Photocatalytic hydrogen evolution experiments showed that the CoSx@VS-In2S3 nanohybrids delivered an attractive photocatalytic activity of 4.136 mmol h−1 g−1 under visible-light irradiation, which was 8.23 times higher than that of the pristine In2S3 samples. As expected, VS could enhance the charge-separation efficiency of In2S3 through rearranging the electrons of the In2S3 basal plane, in addition to improving the electron-transfer efficiency, as visually verified by transient absorption spectroscopy. Mechanism studies based on density functional theory calculations confirmed that the In atoms adjacent to VS played a key role in the translation, rotation, and transformation of electrons for water reduction. This scalable strategy focused on defect engineering paves a new avenue for the design and assembly of 2D core/shell heterostructures for efficient and robust water-splitting photocatalysts. [ABSTRACT FROM AUTHOR]

Efficient spatial charge separation plays a crucial role in improving the photocatalytic performance. Therefore, 1T/2H MoSe2/BiOCl (1T/2H MS/BOC) and 2H MoSe2/BiOCl (2H MS/BOC) piezo-photocatalysts are synthesized. By combining piezoelectric catalysis and photocatalysis, a highly active piezo-photocatalytic process is realized. The optimal 1T/2H MS/BOC piezo-photocatalyst displays superior diclofenac (DCF) degradation and hydrogen (H2) evolution activity under the combined action of ultrasound and light. In particular, the DCF degradation kinetic constant (k) of optimal 0.5% 1T/2H MS/BOC under the synergistic effect of ultrasound and light is 0.057 min−1, which is 8.1 and 6.3 times higher than those of BiOCl (0.007 min−1) and 0.5% 2H MS/BOC (0.009 min−1). Moreover, the H2 evolution rate of 0.5% 1T/2H MS/BOC is 122.5 μmol g−1 h−1, which is also higher than those of BiOCl (45.8 μmol g−1 h−1) and 2H MS/BOC (49.5 μmol g−1 h−1). The dramatic improvement in the DCF degradation and H2 evolution piezo-photocatalytic performance of 1T/2H MS/BOC catalysts is ascribed to the built-in polarization electric field and abundance of active sites of 1T/2H MS/BOC as well as the advantageous band structure between BiOCl and 1T/2H MoSe2. Additionally, three probable degradation pathways of DCF were put forward from the results of liquid chromatography-mass spectrometry (LCMS) and density functional theory (DFT) calculations. This study provides the design strategy of high efficiency piezo-photocatalysts in environmental purification and energy-generation fields based on phase and band structure engineering. [ABSTRACT FROM AUTHOR]

Half-sandwich complexes [Ru(η6-pcym)(L1)X]PF6 (1, 3) and [Ir(η5-Cp*)(L1)X]PF6 (2, 4) featuring a thiadiazole-based ligand L1 (2-(furan-2-yl)-5-(pyridin-2-yl)-1,3,4-thiadiazole) were synthesized and characterized by varied analytical methods, including single-crystal X-ray diffraction (X = Cl or I, pcym = p-cymene, Cp* = pentamethylcyclopentadienyl). The structures of the molecules were analysed and interpreted using computational methods such as Density Functional Theory (DFT) and Quantum Theory of Atoms in Molecules (QT-AIM). A 1H NMR spectroscopy study showed that complexes 1–3 exhibited hydrolytic stability while 4 underwent partial iodido/chlorido ligand exchange in phosphate-buffered saline. Moreover, 1–4 demonstrated the ability to oxidize NADH (reduced nicotinamide adenine dinucleotide) to NAD+ with Ir(III) complexes 2 and 4 displaying higher catalytic activity compared to their Ru(II) analogues. None of the complexes interacted with reduced glutathione (GSH). Additionally, 1–4 exhibited greater lipophilicity than cisplatin. In vitro biological analyses were performed in healthy cell lines (CCD-18Co colon and CCD-1072Sk foreskin fibroblasts) as well as in cisplatin-sensitive (A2780) and -resistant (A2780cis) ovarian cancer cell lines. The results indicated that Ir(III) complexes 2 and 4 had no effect on human fibroblasts, demonstrating their selectivity. In contrast, complexes 1 and 4 exhibited moderate inhibitory effects on the metabolic and proliferation activities of the cancer cells tested (selectivity index SI > 3.4 for 4 and 2.6 for cisplatin; SI = IC50(A2780)/IC50(CCD-18Co)), including the cisplatin-resistant cancer cell line. Based on these findings, it is possible to emphasize that mainly complex 4 could represent a further step in the development of selective and highly effective anticancer agents, particularly against resistant tumour types. [ABSTRACT FROM AUTHOR]

Gold–silver (Au–Ag) nanocrystals with a combination of concave surface and hollow interior are of great interest due to their distinctive structural merits. Herein, we introduce a facile strategy based on seed surface doping to create concave Au@AuAg yolk–shell nanocubes with surface concavity (Au@AuAg YSCNCs), and examine their intriguing properties in optics and catalysis. In particular, the Au@Ag core–shell nanocubes are generated and reacted with sodium thiosulfate, followed by the addition of HAuCl4 to remove Ag atoms on the side walls and deposit Au/Ag atoms on the corners/edges via the galvanic replacement reaction. UV-vis extinction spectra show that compared to Au@Ag core–shell nanocubes, the current Au@AuAg YSCNCs enable a redshift in the major absorption peak, which should be attributed to the increase in charge polarization regions. Meanwhile, the structural advantage is validated using the reduction of 4-nitrophenol as the model reaction. In particular, the current Au@AuAg YSCNCs exhibit an enhanced catalytic efficiency compared to the Au@Ag core–shell nanocubes. Mechanism study using density functional theory reveals that the structural advantage boosts the catalytic activity by upshifting the d-band center and thus lowering the activation barrier. The current study provides a feasible strategy to integrate two structural features (e.g., concave surface and hollow interior) into one AuAg nano-entity, which could be potentially extended to other metals and/or alloys. [ABSTRACT FROM AUTHOR]

Drugs that inhibit cytochrome P450 (P450) enzymes through mechanism-based inactivation (MBI) can significantly affect metabolic interactions, often leading to adverse effects. Despite this, the MBI of P450 is not an uncommon occurrence, as evidenced by numerous previous studies. In our investigation, we used Density Functional Theory (DFT) calculations to delve into the MBI of P450 by chloramphenicol (CP), evaluating the energy profiles of five possible pathways for this process. Furthermore, we conducted a multitargeted molecular modeling analysis to discern the binding profile of CP at the active site of five distinct P450 isozymes. Our molecular modeling results reveal that CP demonstrates a high degree of compatibility with various P450 isoforms' binding sites, owing to its low binding energies, the presence of a dense network of polar and hydrophobic interacting residues, and the involvement of key residues in the binding interactions. Our DFT calculations suggest that CP is a potent P450 inhibitor, primarily due to the availability of two thermodynamically favored interaction sites on CP structure vulnerable to P450 interaction. Our comparative analysis indicates that P450's inactivation by CP principally proceeds via the C–H hydroxylation of the dichloromethane and hydroxymethylene binding sites present in the CP structure. [ABSTRACT FROM AUTHOR]

2-Amino-N-(phenylcarbamothioyl)benzamide (APCB), an amino benzoyl thiourea derivative, was synthesized via ring opening nucleophilic substitution reaction. Various spectroscopic techniques, including UV-Vis, FT-IR, and NMR spectroscopy, were used to fully characterize the synthesized thiourea derivative. A comprehensive theoretical study was conducted utilizing density functional theory (DFT) and the B3LYP functional along with 6-311++G(d,p) basis sets to justify the experimental results. NMR chemical shifts were computed, illustrating that the molecule exhibits several intramolecular hydrogen bonds influencing proton assignment. Furthermore, the experimental UV-Vis spectrum was interpreted by incorporating time-dependent density functional theory (TD-DFT) calculations for numerous singlet excited states. Thus, both single and mixed transitions are disclosed. Moreover, DFT calculations were employed for frontier molecular orbitals (FMOs) analysis, non-linear optical (NLO) properties, and calculated thermodynamic functions. The reactivity of different sites is precisely assigned by implementing the molecular electrostatic potential map analysis and the Fukui functions. In addition, the non-covalent interaction was visualized through the reduced density gradient (RDG) function, confirming the existence of N–H⋯O intramolecular H-bond interaction. In contrast, a localized orbital locator (LOL) function explains the various covalent interactions in the molecule. Molecular docking properties and drug-likeness calculations were implemented according to Lipinski's five principles. In terms of biological evaluation, the lead molecule was evaluated as a novel VEGFR-2 inhibitor (IC50 = 35.78 ± 3.06 μM) for treating breast cancer (IC50 = 177.180 ± 5.760 μM). Overall, our study highlights the power of DFT calculations to interpret the spectral data of a synthetic amino benzoyl thiourea derivative, a versatile building block for functional compounds with tailored properties and applications. [ABSTRACT FROM AUTHOR]

In this work, particle swarm optimization (CALYPSO) is combined with density functional theory (DFT) to perform a comprehensive structure search for the Bn0/−Rb2 (n = 1–12) clusters. The ground-state structures of the Bn0/−Rb2 (n = 1–12) clusters were determined based on the total energy of the obtained structures. It was also found that when the number of B atoms was low, the doped cluster geometry mainly behaved as planar or planar-like. The addition of doped Rb atoms distorts the boron clusters, with the doping position around the main body of boron. The stability analysis shows that the B8Rb2 cluster with a double pyramidal structure and a symmetry of D7h has excellent stability in the studied system. The energy gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital is 6.14 eV. Bonding analysis is performed using molecular orbitals and density of states, and the results show that strong communications between the two Rb atoms and the B-atom bulk dominate their significant stability, where mainly the p atom orbital of the Rb atoms interacts with the s and p atom orbitals of the B atoms. Furthermore, the bond level density and naturally adapted orbital analysis revealed that the formation of effective π-type naturally adapted orbitals between the doped Rb atoms and the B atoms, with a higher delocalization index, is one of the reasons for the higher cluster stability. [ABSTRACT FROM AUTHOR]

The Co-based heterojunction is regarded as an efficient material for the oxygen evolution reaction (OER), but the synthesis is still time- and labor-consuming, and environmentally unfriendly. Herein, we propose a green and facile L -lysine-induced strategy for the successful synthesis of porous CoS/Co3O4 nanoframes (NFs). L -Lysine played a pivotal role in facilitating the formation of the stable Co(OH)2 nanosheet precursor, which was subsequently in situ converted into CoS/Co3O4 NFs through the sulfuration treatment. The resulting CoS/Co3O4 NFs showed a low overpotential of 304 mV at 10 mA cm−2 and remarkable long-range durability in 1.0 M KOH for the OER. The rechargeable Zn–air battery exhibited high charge–discharge cycling stability (>120 h) with CoS/Co3O4 NFs + Pt/C as an air cathode. Density functional theory calculations demonstrated that the charge density of the CoS/Co3O4 heterostructure can be redistributed by rebalancing the Fermi level after the contact between CoS and Co3O4, potentially modulating the pristine catalytic properties of single components. This work provides a facile and green synthesis strategy for developing efficient Co-based catalysts in sustainable energy conversion devices. [ABSTRACT FROM AUTHOR]

The design of organic molecules as drug molecules holds tremendous promise for success in both the present and future. Among the various types of compounds, heterocyclic compounds play a crucial role as they are extensively found in nature and are vital for life's processes. Their widespread presence and importance make them invaluable in the field of drug discovery and development. In this study, we present a thorough examination of 4-methylthiazole compounds (MTs) that are synthesized using a simple, straightforward protocol. Our analysis aims to provide a comprehensive understanding of these compounds. Various techniques, including proton and carbon NMR, mass spectrometry, FT-IR, and UV spectroscopy, are employed to perform an in-depth characterization of the MTs. The molecular structures of the synthesized substances, namely 6, 7, and 9, are investigated using density functional theory (DFT) with 6-311++G(d,p) as the basis set. By utilizing the DFT/B3LYP technique, the polarizability (α0) and first hyperpolarizability (β0) values are determined. Notably, the computed results for β0 suggested the potential presence of non-linear optical (NLO) behavior in all the molecules. Furthermore, the energies of the highest occupied molecular orbital (HOMO), the lowest unoccupied molecular orbital (LUMO), and the molecular electrostatic potential (MEP) are calculated and thoroughly examined to gain insights into the reactive sites of the molecules. The MEP surface is used to comprehend the locations of reactivity within the molecule. Additionally, the Mulliken atomic charges of carbon, oxygen, and nitrogen atoms are calculated using the same basis set. The anti-inflammatory and anti-diabetic properties of MTs are evaluated using protein denaturation and α-amylase inhibitory methods, respectively. Remarkably, the MTs demonstrated greater effectiveness compared to the standard drugs diclofenac and acarbose, respectively, indicating their potential as potent therapeutics for inflammation and diabetes treatment. [ABSTRACT FROM AUTHOR]

Herein, we investigated the α-acetoxylation of ketones through various experiments. These include screening of reaction conditions, analysis of reactivity and selectivity over diverse ketones, kinetic study of the reaction of monoacetoxylation and diacetoxylation, density functional theory calculations for estimating the energy and structure, and analysis of natural bond orbitals. Based on the reaction products of the study, the pseudo first-order model is determined as the best model for the reaction, and the identification of the reaction intermediates indicates that iodonium is an essential intermediate in the reaction. Additionally, kinetic studies and theoretical calculations reveal that the reaction may utilize a different mechanism depending on the ketone structure; in this case, however, we focused on the α-acetoxylation of 4-tert-butylcyclohexanone. Based on these findings, we propose a reaction mechanism and the corresponding behavior description for iodine(III) in α-acetoxylation reactions. [ABSTRACT FROM AUTHOR]

A reaction between CoCl2 and L3-(CO2−)2 (2 : 1 stoichiometry) in CH3OH affords a discrete complex [Co II4- {L3-(CO2−)2}2(μ3-OCH3)2(CH3OH)2(H2O)2Cl2] (1) [L3-(CO2−)2 = 3-[N-{2-(pyridin-2-yl)methyl}amino]-bis(propionate)]. The structure of 1 reveals two terminal mononuclear CoII{L3-(CO2−)2}Cl units connected by a dimeric Co II2 (μ3-OCH3)2(CH3OH)2(H2O) unit present in the centre through two methoxo (μ3-OCH3)- and two carboxylate (μ-1,1-OCO-) bridges affording a tetranuclear coordination cluster of Co(II) with a defective dicubane topology. In 1, Co1 (terminal) has distorted octahedral CoIIN2O3Cl and the central Co2 has CoIIO6 coordination. Such coordination arrangements afford the observed topology. Variable-temperature magnetic studies reveal anti-ferromagnetic coupling in 1. Three magnetic exchange interactions (one anti-ferromagnetic and two ferromagnetic: J1 = +3.3 cm−1 (Co⋯Co 3.176 Å; μ-1,1-OCO- and μ3-OCH3 bridges), J2 = −2.5 cm−1 (Co⋯Co 3.228 Å; μ-1-OCO- and μ3-OCH3 bridges) and J3 = +10.6 cm−1 (Co⋯Co 3.084 Å; two μ3-OCH3 bridges)) have been identified, with the inclusion of the orbital reduction parameter (α = Aκ = 1.38), spin–orbit coupling (λ = −158 cm−1) and axial distortion (energy gap Δ = −975 cm−1 between singlet and doublet levels), rationalized by density functional theory (DFT) calculations. [ABSTRACT FROM AUTHOR]

The oxygen reduction reaction (ORR) is deemed a sustainable energy source; however, developing green, earth-abundant, and efficient noble-metal-free catalysts for efficient ORR in different media remains a grand challenge. Herein, we present a scalable, facile, environmentally benign, and one-pot strategy for the fabrication of eco-friendly nitrogen-enriched graphitic-like hierarchical porous sub-100 nm carbon (denoted as N-HMPC) nanocapsules with controllable N-content for ORR. The synthesis route is based on in situ organic-organic self-assembly of Pluronic F127 copolymer micelles and resorcinol–melamine–formaldehyde in the presence of a silica template followed by carbonization and eroding the silica core. The as-formed N-HMPC nanocapsules have a core–shell morphology (∼84 nm), hierarchical porosity, high surface area of (790 m2 g−1), and tunable nitrogen content (9–25%). Intriguingly, N-HMPC nanocapsules exhibit an analogous ORR activity to the commercial Pt/C catalyst (20% Pt) in the alkaline and acidic electrolytes, besides superior durability and inimitable tolerance to methanol and CO poisonings due to the hollow core–shell architecture and abundant nitrogen. A judicious combination of experimental and density functional theory (DFT) simulations delineated the ORR pathway and mechanism for N-HMPC in acidic and alkaline electrolytes. The presented approach may open new avenues for the rational design of metal-free green electrocatalysts for ORR. [ABSTRACT FROM AUTHOR]

The hydroboration of alkynes with bis(pinacolato)diboron (B2pin2) using H2O or untreated H2O as a solvent is a challenging task. This work reports the aqueous N-heterocyclic carbene (NHC)-catalyzed hydroboration of alkynes with B2pin2, in which a wide range of alkynes with different functional groups are tolerated. The proposed NHC active species are formed through a nonclassical strategy in contrast to the traditional method involving deprotonation of the imidazolium salts in the presence of a base. The proposed NHC-catalyzed hydroboration process can be performed using untreated H2O as a solvent under an air atmosphere in the absence of exogenous bases. Mechanistic investigations, including control experiments, Fourier transform infrared spectroscopy, and density functional theory calculations revealed that the NHC generated in situ is the true active species. Moreover, an in situ generated diboron-NHC adduct, which acts as a reservoir of NHC and is critical for the stability of NHC in aqueous media, was isolated and fully characterized. [ABSTRACT FROM AUTHOR]

The research on inorganic nanozymes remains very active since the first paper on the "Intrinsic peroxidase-like properties of ferromagnetic nanoparticles" was published in Nature Nanotechnology in 2007. However, there is still the question, "What are the inorganic nanozymes?" Inorganic nanomaterials with intrinsic enzyme-like activities were not generated from artificial synthesis processing. The unique architecture of the metal site in inorganic nanomaterials contributes to the specificity and catalytic behavior described by the classic Michaelis–Menten equation, just like an enzyme (protein) or ribozyme (RNA), and as supported by density functional theory calculations. The discovered inorganic nanozymes participate in many key biological catalysis processes, especially related to oxygen. Possibly, they were essential to the emergence of life before RNAs and proteins, and they still play a crucial role in our daily lives, especially from the view of biogeochemistry. These inorganic nanozymes are classified as "inorganic enzymes", in line with the existing classifications of enzymes (proteins) and ribozymes (RNAs) as biocatalysts. By drawing inspiration from the metal architecture in nanomaterials, scientists can design artificial biocatalysts or functionalized nanozymes that are more stable and specific. It is necessary to pursue research to utilize inorganic nanozymes in the current biomedical applications and comprehend how they impact our Earth's environment. [ABSTRACT FROM AUTHOR]

Excessive use of tetracycline (TC) exacerbates environmental pollution and seriously threatens human health. Therefore, it is of great significance to explore an effective approach for detecting TC. In this work, a water-stable and ratiometric luminescent sensor based on a dual-emitting Eu-based metal–organic framework (Eu-TCPE, H4TCPE = tetrakis(4-carboxyphenyl)ethylene) was established through a solvothermal method. Benefiting from the luminescence quenching behavior of H4TCPE linkers through the inner filter effect (IFE) and the enhanced fluorescence emission of Eu3+via the antenna effect, supported by the results of UV-vis absorption spectra and density functional theory (DFT) calculations, the Eu-TCPE sensor exhibited a fast and selective response towards TC detection with a low detection limit of 14 nM in a linear range of 0–50 µM. Application of the Eu-TCPE sensor in real samples of tap water and milk was also investigated. Furthermore, a test-strip-based sensor with the Eu-TCPE probe fixed on the surface was developed for the real-time selective detection of TC in aqueous solution, and the fluorescence color changes of the test strip under UV-light excitation can be captured using the portable online analyzer of a smartphone-color detector App, which showed a handheld platform for the rapid and visual detection of TC in practical applications. [ABSTRACT FROM AUTHOR]

The reaction of alkynes with bis-cyclopentadienyl hydride complexes of niobium has aroused substantial concern due to their important roles in catalytic hydrogenation processes. In this paper, the reaction mechanisms of Cp2NbH3 (Cp = η5-C5H5) with substituted alkynes RC≡CR (R = COOMe (1) and Me (2)) were investigated and compared based on density functional theory (DFT) calculations. The calculated results demonstrate that the reaction mechanisms and products of the title reactions are regulated by the characteristics of the alkyne substituent. For alkynes that feature the electron-withdrawing substituent COOMe, the corresponding fumaric ester complex, namely, Cp2NbH(trans-MeO2CCH＝CHCO2Me), can be obtained at ambient temperature through an insertion process. For alkynes that feature the electron-donating substituent Me, the products are hydride niobocene Cp2NbH(MeC≡CMe) and H2, which are obtained via the elimination of hydrogen molecules, and they can only be obtained with irradiation by UV light. Our studies provide reasonable explanations for experimental observations and predict new chemical reactions in this domain. [ABSTRACT FROM AUTHOR]

Synthesis and characterisation of a dithiadiaza chelator NSNS2A, as well as copper complexes thereof are reported in this paper. Solution structures of copper(I / II) complexes were calculated using density functional theory (DFT) and validated by both NMR and EPR spectroscopy. DFT calculations revealed a switch in the orientation of tetragonal distortion upon protonation, which might be responsible for poor stability of the Cu(II)NSNS2A complex in aqueous media, whilst the same switch in tetragonal distortion was experimentally observed by changing the solvent. The chelator was radiolabeled with 64Cu and evaluated using PET/MRI in rats. Despite a favorable redox potential to stabilize the cuprous state in vivo, the 64Cu(II)NSNS2A complex showed suboptimal stability compared to its tetraazamacrocyclic analogue, 64Cu(TE2A), with a significant 64Cu uptake in the liver. [ABSTRACT FROM AUTHOR]

This paper demonstrates the utility of joint applications of X-ray diffraction, solid state (ss) NMR, density functional theory (DFT) and molecular mechanics (MM) calculations for the determination of the stereochemistry of paramagnetic bis(aminoacidato)copper(II) compounds. Solution-based and mechanochemical syntheses of trans-bis(leucinato)copper(II) [Cu(Leu)2] with L - and DL -leucine using different solvents always resulted in the same two-dimensional coordination polymers of the LL (previously reported in the literature) and DL diastereomers. The X-ray crystal and molecular structure of trans-catena-[(μ- D -leucinato)(μ- L -leucinato)copper(II)] (space group C2) has symmetry unrelated D - and L -leucine side-chain conformations. An asymmetrical copper(II) DL -amino acid complex has not been observed so far in a non-centrosymmetric space group. Both LL and DL trans-[Cu(Leu)2] crystals have similar intermolecular bonding. The X-ray powder diffraction and magic-angle spinning (MAS) ssNMR information available from the polycrystalline bulk phase of the two compounds agree with their single-crystal results. Besides, the 2H MAS ssNMR spectrum of the polycrystalline sample synthesized using DL -leucine showed weak signals which were ascribed to a small amount of the LL (DD) stereoisomers. DFT calculations of the Fermi-contact contributions aided the 13C and 2H NMR spectral assignments. DFT conformational analyses of the LL and DL isomers revealed two Leu side-chain conformations as the energetically favorable ones in the gas phase and aqueous solution. These are exactly the conformations whose combinations occur in the observed crystal structures. Similar MM potential energies of LL and DL trans-[Cu(Leu)2] in the crystal lattices suggest that crystallization of DL over LL (DD) diastereomers should be attributed to kinetic rather than thermodynamic effects. [ABSTRACT FROM AUTHOR]

Many enzyme reactions present instantaneous disorder. These dynamic fluctuations in the enzyme-substrate Michaelis complexes generate a wide range of energy barriers that cannot be experimentally observed, but that determine the measured kinetics of the reaction. These individual energy barriers can be calculated using QM/MM methods, but then the problem is how to deal with this dispersion of energy barriers to provide kinetic information. So far, the most usual procedure has implied the so-called exponential average of the energy barriers. In this paper, we discuss the foundations of this method, and we use the free energy perturbation theory to derive an alternative equation to get the Gibbs free energy barrier of the enzyme reaction. In addition, we propose a practical way to implement it. We have chosen four enzyme reactions as examples. In particular, we have studied the hydrolysis of a glycosidic bond catalyzed by the enzyme Thermus thermophilus β-glycosidase, and the mutant Y284P Ttb-gly, and the hydrogen abstraction reactions from C13 and C7 of arachidonic acid catalyzed by the enzyme rabbit 15-lipoxygenase-1.

The lytic polysaccharide monooxygenase (LPMO) enzymes boost polysaccharide depolymerization through oxidative chemistry, which has fueled the hope for more energy-efficient production of biofuel. We have recently proposed a mechanism for the oxidation of the polysaccharide substrate (E. D. Hedegård and U. Ryde, Chem. Sci., 2018, 9, 3866–3880). In this mechanism, intermediates with superoxide, oxyl, as well as hydroxyl (i.e. [CuO2]+, [CuO]+ and [CuOH]2+) cores were involved. These complexes can have both singlet and triplet spin states, and both spin-states may be important for how LPMOs function during catalytic turnover. Previous calculations on LPMOs have exclusively been based on density functional theory (DFT). However, different DFT functionals are known to display large differences for spin-state splittings in transition-metal complexes, and this has also been an issue for LPMOs. In this paper, we study the accuracy of DFT for spin-state splittings in superoxide, oxyl, and hydroxyl intermediates involved in LPMO turnover. As reference we employ multiconfigurational perturbation theory (CASPT2). [ABSTRACT FROM AUTHOR]

Deeply understanding the physical and chemical properties of a melt requires an accurate description of its structure. In this paper, we investigated the structures of Li4GeO4 and Li6Ge2O7 melts which are of interest for growing germanate functional crystals. The structural changes of polycrystalline Li4GeO4 and Li6Ge2O7 from room temperature to their melting temperatures were monitored by Raman spectroscopy and analyzed by density functional theory (DFT) and factor group theory (FGT) calculations. A striking spectral change was observed for polycrystalline Li4GeO4, which is due to the orthorhombic-to-monoclinic phase transition and the Li+ disorder induced by the phase transition. Spectral similarity between monoclinic Li4GeO4 and its corresponding melt indicates that the anion motif of the Li4GeO4 melt is the GeO44− tetrahedron. The Li6Ge2O7 crystal has 180 lattice phonons (45Ag + 45Au + 45Bg + 45Bu) at the centre of the Brillouin zone, including 90 Raman-active phonons (45Ag + 45Bg). All the Raman-active bands were assigned by DFT calculations. The Raman spectrum of polycrystalline Li6Ge2O7 varies smoothly and continuously in the heating/melting process, indicating that the Ge2O76− anion groups in the crystal are preserved in the melt. The disproportionation reaction that often occurs in silicate melts was not found in the Li6Ge2O7 melt. A nucleophilic substitution reaction is proposed to explain the composition-induced structural transformation present in the Li+-rich germanate melts. [ABSTRACT FROM AUTHOR]

This paper reports a systematic quantum chemical study of the complexation of iron(II) phthalocyanine (FePc) and Fe(II)–porphyrazine (FePz) complexes with N-heterocyclic carbenes. The complex can be stabilised either in a singlet or in a triplet state depending on the choice of substituents in the same carbene core. Here, the spin crossover is invoked either via direct bonding or via a dispersion guided non-covalent interaction. Stabilization of intermediate spin of Fe(II) phthalocyanine/Fe(II)–porphyrazine type systems via complexation with carbenes is hitherto unknown. For calculations we have considered a wide range of density functional theory (DFT) levels, including GGA, hybrid and double hybrid functionals. The results obtained using DFT are further supported by domain-based local pair natural orbital-CCSD(T) (DLPNO-CCSD(T)) and multi-configurational self-consistent field (MCSCF) results. [ABSTRACT FROM AUTHOR]

In this paper, a series of mononuclear/binuclear Cu(i) complexes, [CuI(dpq)(PPh3)2](CF3SO3)·CH3OH (1a), [CuI(dppz)(PPh3)2](CF3SO3)·CH3OH (1b), [CuI2(dpq)2(dppm)2](CF3SO3)2 (2a), [CuI2(dppz)2(dppm)2](CF3SO3)2 (2b), [CuI(dpq)(dppp)](CF3SO3)·CH3OH (3a), [CuI(dppz)(dppp)](CF3SO3)·CH3OH (3b), [CuI(dpq)(POP)](CF3SO3)·CH3OH (4a), [CuI(dppz)(POP)](CF3SO3)·CH3OH (4b), [CuI(dpq)(xantphos)](CF3SO3) (5a), and [CuI(dppz)(xantphos)](CF3SO3) (5b) {dppm = 1,1-bis(diphenylphosphino)methane; dppp = 1,3-bis(diphenylphosphino)propane; POP = bis[2-(diphenylphosphino)phenyl]ether; xantphos = 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene; dpq = pyrazino[2,3-f][1,10]-phenanthroline; dppz = dipyrido[3,2-a: 2′,3′-c]phenazine} have been synthesized and characterized by using IR, NMR, elemental analysis, terahertz (THz) time-domain absorption spectroscopy, UV-vis and fluorescence spectroscopy methods as well as single crystal X-ray diffraction analysis. The single crystal X-ray diffraction results indicated that the immediate geometry around each central Cu(i) in the above complexes is a distorted tetrahedron with the central metal atom being coordinated by the two phosphorus atoms of the phosphine ligands and two nitrogen atoms of the bidentate N-containing heterocyclic ligand moieties. It is found that complexes 1a–5a and 5b show photoluminescence in the solid state at room temperature with the highest quantum yield up to 0.5519, and the increased conjugation in the diimine ligands leads to emission reduction along with a red-shift in the emission maxima. Detailed photo-physical studies and density functional theory calculations (DFT) of these complexes have revealed that their lowest energy absorptions and emissions are ascribed to metal-to-ligand charge transfer (MLCT) excited states. The above results indicate that conjugation effects of N-heteroaromatic ligands play a significant role in the emission properties of mononuclear/binuclear Cu(i) complexes. For the first time, terahertz time-domain spectroscopy is applied for qualitatively understanding the photophysical properties of complexes, revealing that terahertz time-domain spectra are sensitive to the weak interaction between the ligands, especially the diimine ligands, and terahertz spectra are strongly correlated with photoluminescence quantum yields of the complexes. [ABSTRACT FROM AUTHOR]

Two noncentrosymmetric alkali calcium borates KCa4(BO3)3 and K0.59Rb0.41Ca4(BO3)3 were synthesized by the high temperature solution method. They both crystallize in the polar space group Ama2 (No. 40). According to our investigation, KCa4(BO3)3 is the only potassium calcium borate and K0.59Rb0.41Ca4(BO3)3 is the first potassium rubidium calcium borate. Two borates both exhibit deep-UV cutoff edges (＜200 nm) and moderate second harmonic generation (SHG) responses. In this paper, the detailed summaries of B–O connection styles in the disorder-free alkali- and alkaline-earth-metal borates have been discussed. Relationships between metal cations and boron atoms are studied. In addition, the optical and thermal property characterization of the two borates was systematically studied. To better understand the structure–property relationships, ab initio density functional theory was employed for the calculation of the optical refractive indices, birefringence and SHG coefficients. Additionally, the SHG density method was used to further explore the spatial distribution of the electronic states dominating the NLO activity. [ABSTRACT FROM AUTHOR]

In this paper, the ionic liquid (IL), 1-octyl-3-methylimidazolium hexafluorophosphate ([Omim][PF6]), was employed to synthesize β-cyclodextrin (β-CD)-functionalized carbon nanotubes/TiO2 (IL–CD-CNTs/TiO2) nanocomposite via a one-pot solvothermal process. The as-prepared product was characterized by SEM, TEM, XRD, TG, FT-IR, EIS, and so forth. Coupled with an aspirated in-syringe device, IL–CD-CNTs/TiO2 could yield the rapid removal of water contaminants within 8 min. In addition to the excellent adsorption capacity, this dual-functional photocatalyst also showed enhanced photocatalytic activity under visible light at a degradation rate of 97% within 180 min. The photocatalytic mechanism based on the formation of the inclusion complex, density functional theory, and electronic structure of IL–CD-CNTs/TiO2 was comprehensively discussed. The IL not only served as the reaction medium but also played a crucial role in improving the adsorption capacity and photocatalytic activity. By exhibiting a strong electron-donating character, IL could promote efficient charge transfer, inhibiting the recombination of photogenerated electron–hole pairs. The as-prepared photocatalyst―capable of rapid adsorption and photodegradation―can meet the requirements of practical applications and reveals a promising direction toward wastewater treatment. [ABSTRACT FROM AUTHOR]

In this study, the photovoltaic performance of van der Waals heterostructure (v-HS) PtS2/ZrS2 has been examined using density functional theory based on first-principle calculations. Out of six possible configurations of v-HS of PtS2/ZrS2, the most stable configuration of v-HS of PtS2/ZrS2 has been identified based on adhesion energy and phonon dispersion relation. The Heyd–Scuseria–Ernzerhof functional has been employed for the calculation of the electronic properties, which has shown that the v-HS PtS2/ZrS2 possesses a type II indirect band gap. The results based on the absorption coefficient have indicated that the v-HS of PtS2/ZrS2 has enhanced absorption when compared to its constituent monolayers PtS2 and ZrS2, with absorption starting from the visible region of the electromagnetic spectrum and achieves the highest value in the ultraviolet region of the electromagnetic spectrum. Solar parameters have been calculated using the Shockley–Queisser method, and the v-HS of PtS2/ZrS2 has been found to exhibit enhanced photovoltaic performance when compared to monolayers PtS2 and ZrS2. These findings suggest that the material has potential applications in both photovoltaics and optoelectronic devices as well as its other applications. [ABSTRACT FROM AUTHOR]

Using 4-aminobenzonitrile (4-ABN) as a ligand and different anions, five cadmium coordination polymers of the formulae [Cd(4-ABN)I2]n (1), [Cd(4-ABN)Br2]n (2), [Cd(4-ABN)2(NO3)2]n (3), [Cd(4-ABN)2(OAc)2]n (4) and {[Cd(4-ABN)2(H2O)2](ClO4)2}n (5) are synthesized and structurally characterized. By changing the anion used, different structural motifs were formed. Compounds 1, 4 and 5 are 1D coordination polymers, while compounds 2 and 3 represent 3D and 2D coordination polymers, respectively. Also, Hirshfeld surface analysis and density functional theory (DFT) calculation on crystalline systems have been performed. [ABSTRACT FROM AUTHOR]

Iridium-based metallization complexes constitute the preferred phosphor materials for organic light-emitting diodes (OLEDs). In this study, we examine the influence of ligands with different N-substitution modes and heavy atom effects on transition metal complexes. Our findings offer valuable insights into the properties of these complexes, facilitating the design and optimization of materials with desired characteristics. By employing density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations, we investigate the thermal vibration correlation function rate theory for Ir(III) tri-dentate ligand complexes that possess exceptional phosphorescence efficiency and broad application prospects. We draw three main conclusions from our investigations. Firstly, substituting 9-N-phenyl and 10-2N-phenyl in the iridium complex Ir(ppy)3 reduces spin–orbit coupling (SOC), resulting in decreased non-radiative rate constants compared to Ir(ppy)3. Conversely, substituting 10-N-phenyl and 11-N-phenyl enhances SOC, leading to varying degrees of increased non-radiative rate constants. Among these, substituting 11-N-phenyl exhibits the highest non-radiative rate constant. Secondly, for the ligand pyridine ring of Ir(ppy)3, 1,3-2N-substitution reduces the reorganization energy while slightly increasing the SOC. Moreover, the energy barrier through the non-radiative path of the metal-centered (MC) state significantly increases. Consequently, the non-radiative decay rate decreases by a factor of 3.1, outperforming other schemes. Notably, 1,2-2N-substitution substantially raises the reorganization energy (by 2.1 times) and SOC, resulting in a five-order increase in the non-radiative decay rate. Therefore, adjacent N-substitutions should be avoided. Thirdly, the crucial activation barriers for the thermal non-radiative deactivation process in compounds 3 and 4 were determined to be 12.61 and 26.04 kcal mol−1, respectively. Compound 4 exhibits the highest non-radiative rate constant (9.68 E + 12), demonstrating that Br substitution on the pyridine of Ir(ppy)3 significantly enhances the non-radiative rate constant. Overall, this study provides valuable insights into the rational design of efficient fluorescent materials based on transition organometallic complexes. [ABSTRACT FROM AUTHOR]

Hydrodeoxygenation (HDO) is an indispensable approach to produce renewable biofuels and value-added chemicals using natural biomass and its derivatives. 2,5-Dimethylfuran (DMF) is considered to be a very promising liquid biofuel, and it can be fabricated by HDO of the biomass derivative 5-hydroxymethylfurfural (HMF). Herein, a highly efficient bifunctional catalyst, Co/HAP(Ce), was fabricated by anchoring highly dispersed Co on Ce-doped hydroxyapatite (HAP(Ce)). Co/HAP(Ce) displayed excellent HDO catalytic activity to convert HMF to DMF, and 99% HMF conversion and 96% DMF selectivity can be obtained under 150 °C, 2 MPa H2 conditions for 5 h. Density functional theory calculations revealed that H2 can be more easily activated by Co/HAP(Ce). Systematic studies confirmed that the high activity of Co/HAP(Ce) can be ascribed to the desired acid–alkali properties, highly dispersed cobalt species and strong metal–support interactions. This research provides a cost effective approach for designing efficient catalysts for HDO of biomass and its derivatives. [ABSTRACT FROM AUTHOR]

A series of trianion assemblies of hexaazatriphenylenehexacarbonitrile {HAT(CN)6} and hexaazatrinaphthylenehexacarbonitrile {HATNA(CN)6} with three Fe(II) or Co(II) ions: {cryptand(K+)}3·{HATNA(CN)6·(FeIII2)3}3−·2C6H4Cl2 (1), {cryptand(K+)}3·{HATNA(CN)6·(CoIII2)3}3−·2C6H4Cl2 (2), and (CV+)3·{HAT(CN)6·(CoIICl2)3}3−·0.5(CVCl)·2.5C6H4Cl2 (3) are synthesized (CVCl = crystal violet). Salt 1 has a χMT value of 9.80 emu K mol−1 at 300 K, indicating a contribution of three high-spin FeII (S = 2) and one S = 1/2 of HATNA(CN)6˙3−. The χMT value increases with cooling up to 12.92 emu K mol−1 at 28 K, providing a positive Weiss temperature of +20 K. Such behavior is described using a strong antiferromagnetic coupling between S = 2 and S = 1/2 with J1 = −82.1 cm−1 and a weaker FeII–FeII antiferromagnetic coupling with J2 = −7.0 cm−1. As a result, the spins of three Fe(II) ions (S = 2) align parallel to each other forming a high-spin S = 11/2 system. Density functional theory (DFT) calculations support a high-spin state of CoII (S = 3/2) for 2 and 3. However, the χMT value of 2 and 3 is 2.25 emu K mol−1 at 300 K, which is smaller than 6 emu K mol−1 calculated for the system with three independent S = 3/2 and one S = 1/2 spins. In contrast to 1, the χMT values decrease with cooling to 0.13–0.36 emu K mol−1 at 1.9 K, indicating that spins of cobalt atoms align antiparallel to each other. Data fitting using PHI software for the model consisting of three high-spin Co(II) ions and an S = 1/2 radical ligand shows very large CoII–L˙3− coupling for 2 and 3 with J1 values of −442 and −349 cm−1. The CoII–CoII coupling via the ligand (J2) is also large, being −100 and −84 cm−1, respectively, which is more than 10 times larger than that of 1. One of the reasons for the J2 increase may be the shortening of the Co–N(L) bonds in 3 and 2 to 2.02(2) and 1.993(12) Å. DFT calculations support the population of the quartet state for the Co3 system, whereas the high-spin decet (S = 9/2) state is positioned higher by 680 cm−1 and is not populated at 300 K. This is explained by the large CoII–CoII coupling. Thus, a balance between J1 and J2 couplings provides parallel or antiparallel alignment of the FeII and CoII spins, leading to high- or low-spin ground states of {L·[MII(Hal)2]3}3−. [ABSTRACT FROM AUTHOR]

The slow redox kinetics and shuttling behavior of the intermediate lithium polysulfides constrain the further development of lithium–sulfur (Li–S) electrochemistry. A yolk–shell In2S3@void@carbon hybrid engineered to host the sulfur for Li–S batteries is prepared by using a multi-layered assembly method. The In2S3/electrolyte interface acted as powerful adsorption and activation sites for soluble polysulfides, which is demonstrated using density functional theory (DFT) calculations. Moreover, the carbon shell provides redundancy for volume-changes during the cycles. The results indicate that yolk–shell In2S3@S@C hybrid cathode shows good reversibility and rate capability, which preserves 563.6 mA h g−1 after 500 cycles at 0.5 C, indicating the potential for developing high-performance battery systems. [ABSTRACT FROM AUTHOR]

The radiative and nonradiative decay processes of a series of Au(III) complexes were investigated using density functional theory (DFT) and time-dependent density functional theory (TDDFT) to explore the influence of graphene quantum dots (GQDs) as ligands on the emission properties and phosphorescence quantum yields. The absorption curves, emission wavelengths, hole–electron analysis, spin density analysis, and spin–orbit coupling (SOC) matrix elements were utilized for a better understanding of the radiation decay rate constants and photoinactivation mechanisms. Our study reveals that adding GQDs as ligands into Au(III) complexes has little impact on their structural stability. Moreover, we found that the fusion of GQDs helps in stabilizing the ground and excited states of Au(III) metal complexes. Importantly, our findings suggest that GQDs have a beneficial effect on the phosphorescence emission process, for instance, suppressing the nonradiative leap and enhancing the phosphorescence quantum yield. Furthermore, the results of the hole–electron analysis show that the addition of GQDs largely reduces the MC leap of Au1, favorably increasing the probability of radiative decay. Spin density analysis also indicates the suppression of 3MLCT characteristics in Au2 and Au3 complexes with GQD ligands. Interestingly, our calculations also reveal that the energy barrier of Au2 is higher than that of Au1 in the 3ES → 3MC transition in the photoinactivation pathway, leading to a higher phosphorescence quantum yield. Overall, we have demonstrated the significant potential of GQDs as stabilizers in our tridentate Au(III) complexes and provided important molecular insights for efficient phosphorescence emission. [ABSTRACT FROM AUTHOR]

In the present contribution, the following three cyclometallated Ir(III) complexes were theoretically investigated using density functional theory calculations to explain their different photophysical properties: [Ir(ppy)2(bpy)]+, where Hppy is 2-phenylpyridine and bpy is 2,2′-bipyridine, [Ir(ppy)2(pbpy)]+, where pbpy is 6-phenyl-2,2′-bipyridine, and [Ir(ppy)2(dpbpy)]+, where dpbpy is 6,6′-diphenyl-2,2′-bipyridine. Despite sharing the same molecular skeleton, with the only difference being the addition of one or two phenyl groups attached to the ancillary bpy ligand, the complexes show different emission quantum yields in CH2Cl2 solution (0.196, 0.049 and 0.036, respectively). Such a behavior was previously justified as a consequence of a different ability to non-radiatively decay through an axial metal-centered (MC) triplet state. In the present contribution, a new non-radiative decay path has been characterized to be mediated by the so-called equatorial MC states, in which an Ir–Nbpy bond is elongated instead of an Ir–Nppy bond as observed in the axial MC states. The decay path involving the equatorial MC states is more favorable than that associated with the axial MC states, and the different ability to decay through the former better explains the photoemission properties exhibited by the three complexes. [ABSTRACT FROM AUTHOR]

Regioselective B–H activation of o-carboranes is an effective way for constructing o-carborane derivatives, which have broad applications in medicine, catalysis and the wider chemical industry. However, the mechanistic basis for the observed selectivities remains unresolved. Herein, a series of density functional theory (DFT) calculations were employed to characterise the palladium N-heterocyclic carbene (Pd-NHC) catalysed regioselective B(3,6)-diarylation of o-carboranes. Computational results at the IDSCRF(ether)-LC-ωPBE/BS1 and IDSCRF(ether)-LC-ωPBE/BS2 levels showed that the reaction undergoes a Pd(0) → Pd(II) → Pd(0) oxidation/reduction cycle, with the regioselective B(3)–H activation being the rate-determining step (RDS) for the full reaction profile. The computed RDS free energy barrier of 24.3 kcal mol−1 agrees well with the 82% yield of B(3,6)-diphenyl-o-carborane in ether solution at 298 K after 24 hours of reaction. The Ag2CO3 additive was shown to play a crucial role in lowering the RDS free energy barrier and facilitating the reaction. Natural charge population (NPA) and molecular surface electrostatic potential (ESP) analyses successfully predicted the experimentally observed regioselectivities, with electronic effects being revealed to be the dominant contributors to product selectivity. Steric hindrance was also shown to impact the reaction rate, as revealed by experimental and computational characterisation studies of substituents and ligand effects. Furthermore, computational predictions aligned with the experimental findings that NHC ligands outperform the phosphine ones for this particular reaction. Overall, the observed trends reported in this work are expected to assist in the rational optimisation of the efficiency and regioselectivity of this and related reactions. [ABSTRACT FROM AUTHOR]

Chromate (Cr(VI)) is a highly toxic heavy metal ion that not only endangers human health but also causes environmental pollution. To control and remove Cr(VI) from water more effectively, we report a simple, novel, and rapid detection technique for Cr(VI) in water based on an iron-manganese bimetal-metal organic framework (FexMny-MOF). Firstly, the synthesized FexMny-MOF has a large specific surface area and porosity; for the first time, an MOF with dual mimic enzyme properties is reported, which can catalyze the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) to the blue product in the presence or absence of H2O2. Interestingly, the mimic enzyme properties of FexMny-MOF are enhanced than those of Fe-MOF and Mn-MOF. The free energies of elementary reactions and adsorption energies (Eads) of H2O2 and O2 adsorbed on different materials were calculated by density functional theory (DFT) to verify the mechanism of action of FexMny-MOF. The Fe1Mn1-MOF mimics oxidase-like oxidation of TMB; 8-hydroxyquinoline (8-HQ) is used as the inhibitor of TMB oxidation, and the specific interaction between 8-HQ and Cr(VI) weakens the inhibition of 8-HQ on TMB oxidation to achieve the detection of Cr(VI). The established method has high sensitivity and selectivity with a detection limit of 51 nM and a linear range of 80–3500 nM. This method has been successfully applied to the determination of Cr(VI) in tap water and the Yellow River, showing its great potential in environmental monitoring. [ABSTRACT FROM AUTHOR]

The aggravating extreme climate changes and environmental pollution problems have stimulated the exploration of green alternatives to conventional fossil fuels and green environmental treatments. Photocatalysis is recognized as an outstanding green tool for solving the energy crisis and environmental rehabilitation issues. Restricted by the high cost of precious metals, researchers expect to obtain low-cost, efficient and stable photocatalysts. Herein, CdS materials were derived through MOFs and subsequently combined with CoO to form CdS/CoO heterojunctions. The catalytic ability was evaluated by the photocatalytic degradation of tetracycline hydrochloride (TC) and the photocatalytic production of hydrogen. With the integration of CoO, in terms of TC degradation, CdS/CoO heterojunctions can degrade over 90% of TC within 1 hour. In terms of hydrogen production, compared to CdS alone, the hydrogen production efficiency of the CdS/CoO heterojunction increased by 1.7 times. The initial analysis of the reasons for the enhancement of photocatalytic efficiency was conducted by TEM, XPS and other characterization means. Density functional theory (DFT) calculations verified the existence of a built-in electric field in the CdS/CoO heterojunction, which was the essential reason for the improved catalytic performance, and finally, the presence of ˙O2− and ˙OH in the photocatalytic system was demonstrated by the ESR technique. Based on the carrier separation/transfer pathway in the heterojunction, a simple and novel S-type heterojunction scheme was proposed. [ABSTRACT FROM AUTHOR]

Platinum(II) complexes with salophen ligands bearing carboxy substituents at different positions, [Pt{(COOH)n–salophen}] (n = 2 (1), 3 (2), 1 (3)), were synthesized and characterized by acquiring UV-vis and luminescence spectra. These complexes exhibited systematic variations in absorption spectra depending on the number of carboxy groups, and this effect was attributed to metal–ligand charge transfer with support from density functional theory calculations. The luminescence properties of these complexes were also correlated with structural differences. Complexes 1–3 showed systematic spectral changes by addition of organic acid and base, respectively. This is based on the protonation/deprotonation of the carboxy substituents. Furthermore, aggregation-induced spectra change was investigated in DMSO–H2O mixtures with various proportions of water. Peak shifts in the range of 95 to 105 nm occurred in the absorption spectra in conjunction with pH changes. These variations resulted from molecular aggregation and diffusion associated with protonation/deprotonation of the carboxy groups. Variations in luminescence emission intensity and peak shifts were also observed. This work provides new insights into the correlations between the optical properties of carboxy-appended molecular complexes and pH changes and will assist in the future design of pH sensing devices based on molecular metal complexes. [ABSTRACT FROM AUTHOR]

The mechanism of nickel-catalyzed selective hydroalkylation of 2-aryl-1,3-dienes has been studied using density functional theory (DFT) calculations. A reaction pathway was suggested, which involves the deprotonation of the amide substrate, ligand coordination with the nickel centre, ligand-to-ligand hydrogen transfer (LLHT) and finally nucleophilic attack. Analysis of the calculated energy profiles shows that the rate-determining step is the LLHT process. For the LLHT step, hydrogen transferring to the least sterically hindered C4 position of 1,3-diene to form a metal-π-allyl intermediate needs the lowest activation barrier because the allylic-Ni intermediate is the most stable. The allyl group binding to the metal centre in an η3 fashion also promotes the following nucleophilic attack owing to the electron-withdrawing capability of the metal. The subsequent nucleophilic attack leads to regio-divergent products with a different substrate. For a linear amide substrate, nucleophiles selectively attack the least hindered terminus carbon of the π-allyl–Ni species to form 1,4-addition products due to the steric effect. However, for a cyclic imide substrate, nucleophiles selectively attack the nonterminal carbon leading to 3,4-selective products, which is supposed to be a result of the electron-withdrawing capability of heteroatoms on the cyclic imide. Furthermore, on combining a cyclic imide substrate and a chiral ligand, a stereoselective 3,4-addition product is obtained due to steric effects. All the calculation results are in agreement with the experimental results. An alternative pathway which includes the step of hydrometalation from the nickel-hydride complex to the diene and the reductive elimination is ruled out due to the calculated high-energy barrier that cannot be achieved under the experimental conditions. [ABSTRACT FROM AUTHOR]