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Buckybowls have been drawing considerable attention because of their unique electronic structures and physical properties. However, few studies have investigated their magnetic properties. In the present investigation on organic molecular magnets, flatly conjugated structures are generally used as couplers. However, there are few reports on the use of curvature couplers for constructing molecular magnets. In this study, a series of dual nitroxide diradical molecular magnets are designed with triphenylene and its edge-modified derivatives (by the –CH2–, –NH–, or –O– edge-bridging groups) as the couplers, and their magnetic coupling properties are studied at the density functional theory level. It is interesting to note that all the designed diradicals exhibit antiferromagnetic (AFM) properties and the curvature of the coupler can considerably enhance their magnetic coupling strength. The curvature of the coupler can reduce its aromaticity and increase the spin polarization of nitroxide groups, thereby enhancing the AFM. The electronic properties of the bridging groups (such as –NH–, –O–) can further enhance the AFM coupling strength of the diradicals by manipulating the π electron distribution on the coupler, especially with the assistance of intramolecular H-bonds for the –NH– edge-bridge. This study provides insights into the magnetic modulation of molecular magnets through the curvature of couplers and also offers valuable information on constructing curved molecular magnets. [ABSTRACT FROM AUTHOR]

The accumulation of gypsum waste (GW), such as flue gas desulfurisation gypsum and phosphogypsum, which remains in regulated stacks occupying considerable land resources, is causing significant environment problems worldwide. A promising strategy for treatment and recycling of GW is to convert GW into higher-valued anhydrite, but the traditional energy-intensive calcination method significantly increases the cost of recovery. Here, we report the first solid-like dehydration of gypsum to produce anhydrite at room temperature. Specifically, a 39 nm thick sulfuric acid film (NSF) was fabricated to extract water of crystallization from gypsum and simultaneously enable a phase transformation from gypsum to anhydrite via recrystallization. Using density functional theory calculations, we obtained the activity (0.025) of crystalline water in gypsum, which is higher than the corresponding value in NSF, so that the dehydration can occur spontaneously. Using our developed kinetic model, we attributed the acceleration of this transformation to the lower nucleation potential (56 kJ mol−1) of anhydrite and the more efficient transfer of the mass (several orders of magnitude higher than that for heating gypsum powders) required for growth. This model allows prediction of nucleation and growth contributions from kinetic data for any given recrystallization system. This work not only demonstrates a new type of recrystallization reaction driven by a nano-film reservoir, which differs from bulk solution–solid and gas–solid reactions but also provides a promising strategy for energy-efficient recycling of anhydrite from gypsum waste. [ABSTRACT FROM AUTHOR]

The slow kinetics of the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) in air cathodes severely limit the development of reversible zinc–air batteries. Thus, bifunctional oxygen catalysts with excellent electrocatalytic activity and durability for both the oxygen reduction and oxygen evolution reactions (ORR/OER) are keys to achieving long-term rechargeable zinc–air batteries. However, it remains challenging to further improve the performance by adding more active sites. To address this, a series of nitrogen-doped carbon (CN) with NiCo alloys has been synthesized by pyrolyzing a simple bimetal zeolitic-imidazolate framework (ZIF) and then evenly loaded with metallic Ru nanoparticles, resulting in Ru–NiCo/NC samples. Benefiting from the large pore volume and high activities, the Ru–NiCo/NC electrocatalysts exhibit higher ORR (E1/2 = 0.84 V) and OER performance with an overpotential of 342 mV at 10 mA cm−2, along with superior cycle stability. More significantly, when employed in rechargeable zinc–air batteries, Ru–NiCo/NC catalysts demonstrate a high power density of 132.3 mW cm−2, significantly outperforming Pt and Ru-based zinc–air batteries. Additionally, DFT (density functional theory) results indicate that the addition of Ru leads to a downshift of the d-band center from the Fermi level, which benefits the reduction of energy barriers and enhances the desorption of O-containing intermediates. This work provides a feasible strategy for developing efficient and high-performance bifunctional electrocatalysts. [ABSTRACT FROM AUTHOR]

Peroxomanganese species have been proposed as key intermediates in the catalytic cycles of both manganese enzymes and synthetic catalysts. However, many of these intermediates have yet to be observed. Here, we report the formation of a series of intermediates, each generated from the reaction of the mononuclear MnIII–hydroxo complex [MnIII(OH)(dpaq2Me)]+ with hydrogen peroxide under slightly different conditions. By changing the acidity of the reaction mixture and/or the quantity of hydrogen peroxide added, we are able to control which intermediate forms. Using a combination of electronic absorption, 1H NMR, EPR, and X-ray absorption spectroscopies, as well as density functional theory (DFT) and complete active space self-consistent field (CASSCF) calculations, we formulate these intermediates as the bis(μ-oxo)dimanganese(III , IV) complex [MnIIIMnIV(μ-O)2(dpaq2Me)2]+, the MnIII–hydroperoxo complex [MnIII(OOH)(dpaq2Me)]+, and the MnIII–peroxo complex [MnIII(O2)(dpaq2Me)]. The formation of the MnIII–hydroperoxo species from the reaction of a MnIII–hydroxo complex with hydrogen peroxide mimics an elementary reaction proposed for many synthetic manganese catalysts that activate hydrogen peroxide. [ABSTRACT FROM AUTHOR]

As a pseudocapacitor electrode material, molybdenum disulfide (MoS2) usually shows inferior capacity, rate capability and cyclability. Structural regulation and heteroatom doping are the available methods to ameliorate the electrochemical properties of MoS2. Herein, phosphorus doped molybdenum disulfide regulated by sodium chloride (SP-MoS2) is successfully synthesized using phosphomolybdate acid as a molybdenum source and an in situ dopant and sodium chloride (NaCl) as a structural regulator. Under the structural regulation of NaCl, the SP-MoS2 nanosheets exhibit an interweaved architecture with a large interlayer spacing of 0.68 nm. Owing to the in situ P doping and large specific surface area (21.0 m2 g−1), the SP-MoS2 electrode possesses a maximum capacity of 564.8 F g−1 at 1 A g−1 and retains 56.3% of the original capacity at 20 A g−1. Density functional theory (DFT) calculations indicate that SP-MoS2 displays a high K+ average adsorption energy of −3.636 eV. In addition, the fabricated SP-MoS2//AC asymmetric supercapacitor device displays an energy density of 22.8 W h kg−1 at 759 W kg−1. [ABSTRACT FROM AUTHOR]

We have proposed a non-lead oxide-based double perovskite, Bi2FeCrO6 (BFCO), as an absorber in perovskite solar cells (PSCs) to address the concerns associated with toxic and unstable lead-based perovskite materials. Using the WIEN2K code within the density functional theory (DFT) framework, we investigated the structural and optoelectronic properties of BFCO. Additionally, the photovoltaic performance of the n–i–p architecture of a PSC (FTO/TiO2/Bi2FeCrO6/HTL/Au) in the presence of different HTLs (hole transport layers) such as spiro-OMeTAD, Cu2O, and P3HT and TiO2 as the ETL (electron transport layer) is analyzed through the simulation tool SCAPS-1D. The bandgap of BFCO was calculated to be 1.84 eV by using the spin–orbit coupling (SOC) method with the help of the PBE-GGA functional. Optimizing the performance of the PSCs typically involves various parameters, including the absorber thickness (t), bulk and interface defect densities, and the doping density of the BFCO layer. We show that the PSCs with structures FTO/TiO2/Bi2FeCrO6/Cu2O/Au, FTO/TiO2/Bi2FeCrO6/P3HT/Au, and FTO/TiO2/Bi2FeCrO6/spiro-OMeTAD/Au exhibited short circuit current density (Jsc) values of 17.89 mA cm−2, 17.92 mA cm−2 and 17.94 mA cm−2, open circuit voltage (Voc) values of 1.42 V, 1.35 V, and 1.35 V, fill factor (FF) values of 86.76%, 81.98%, and 63.39%, and power conversion efficiencies (PCE) of 22.11%, 20.35% and 15.42%, respectively. Specifically, PSCs with Cu2O as the HTL showed superior performance compared to other studied devices. [ABSTRACT FROM AUTHOR]

The influence of the P–M–P bite angle in diphosphine ligands on selectivity has been observed in various catalytic reactions. A better understanding of the ligand bite angle concept is important for the rational design of efficient catalytic systems. In the present work, the mechanism of cobalt-catalyzed C–H functionalization of aldehydes with enynes and how the diphosphine ligands alter regioselectivity were investigated by density functional theory (DFT) calculations. The catalytic cycle is initiated by the oxidative cyclization of enynes rather than the oxidative addition of aldehydes. Regioselectivity arises from competing σ-bond metathesis and migratory insertion steps, in which the steric effects of diphosphine ligands are the dominant factors influencing the activation barriers. The calculations indicate that σ-bond metathesis is more challenging and its feasibility is highly dependent on the ligand bite angle. The improved mechanistic understanding will enable further design of transition-metal-catalyzed selective cyclization reactions. [ABSTRACT FROM AUTHOR]

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]

In a routine synthetic experiment, an elusive macrocyclic organic compound, namely cyclo-di-BADGE, was serendipitously acquired in a single crystalline form. This compound, widely known as a by-product from the co-polymerization reactions of bisphenol A (BPA) and bisphenol A diglycidyl ether (BADGE), has never been comprehensively characterized prior to this work. Herein, NMR and single crystal X-ray diffraction analyses have been conducted to investigate the molecular structural properties of cyclo-di-BADGE in the solution phase and solid state. Systematic conformational studies were carried out using the Conformer-Rotamer Ensemble Sampling Tool (CREST) in conjunction with density functional theory (DFT) calculations. Moreover, the aggregation behavior of cyclo-di-BADGE in organic and aqueous media was investigated through UV-Vis and dynamic light scattering (DLS) analyses. Detailed aggregation mechanisms were further probed by molecular dynamics (MD) simulations. Finally, we investigated the binding of cyclo-di-BADGE with a model protein, bovine serum albumin (BSA), through fluorescence and molecular docking analyses. Our studies provide valuable knowledge to facilitate the understanding of cyclo-di-BADGE in terms of its various physico-chemical properties and relevant effects on the environment and biological systems. [ABSTRACT FROM AUTHOR]

A very simple multifunctional pyrimidine-based hydrazone was designed and developed as an effective tool for the dual-mode fluorescent turn-on detection of Al3+ and Zn2+ ions at two different wavelengths. The probe interestingly displayed blue fluorescence around 440 nm and cyan fluorescence around 470 nm with Al3+ and Zn2+ ions, respectively. Coordination of Al3+/Zn2+ ions with HSAL results in emission enhancement owing to chelation-enhanced fluorescence and inhibition of –CH＝N– isomerization as well as ESIPT. HSAL exhibited excellent sensitivity and selectivity towards the ions with good association constants and nanomolar level LOD values. In turn, HSAL–Al3+ and HSAL–Zn2+ ensembles could selectively and sensitively detect PPi ions among other anions. The overall binding mechanism of the probe towards Al3+/Zn2+ ions was analysed through Job's plot, 1H NMR, mass, and density functional theory experiments. Besides, Al3+ ions could easily replace Zn2+ ions from HSAL–Zn2+ to demonstrate emission attributed to HSAL–Al3+, and also the probe showed a remarkable binding tendency towards Al3+ over Zn2+ ions in the presence of PPi. HSAL is capable of exhibiting reversible switching characteristics on the addition of Al3+/Zn2+ and PPi, which were successfully employed in constructing a logic gate. The excellent sensing characteristics of HSAL were utilized for various cost-effective applications including, real water, cotton swabs, thin film, and tablets. In addition, the compound HSAL was also able to reveal certain multifunctional behaviors like AIE and acidochromism. [ABSTRACT FROM AUTHOR]

Ammonium phosphomolybdate [APM, (NH4)3PMo12O40·xH2O] is a versatile inorganic compound having diverse applications in the catalysis and dielectrics fields and high adsorption capacity for large metal cations due to its negatively charged cage-like structure with hollow cavities. In this study, APM was synthesized via a precipitation method and several parameters, such as the solid-to-liquid ratio (S : L), pH value, initial metal concentrations, adsorption isotherms, temperature effect, adsorption kinetics, shaking time, and interference of multiple ions were investigated for the effective removal of Pb2+ ions from aqueous media. The experimental results revealed that 100% of the Pb2+ ions were successfully adsorbed at the surface of APM at pH values from 2 to 6. Under the optimized conditions, the maximum adsorption capacity of 951.65 mg g−1 for Pb2+ ions on the APM was obtained at an S : L ratio of 0.1 g L−1 based on the Freundlich adsorption model. The adsorption equilibrium was achieved within an hour. The presence of alkali and alkaline metal ions did not interfere with Pb2+ adsorption, indicating the high selectivity toward Pb2+ ions. The Pb2+ ion adsorption mechanism was determined using DFT calculations, which revealed that Pb2+ is likely to interact directly with the 4 O atoms of the H-quadrate site, which hints towards the formation of a PbMoO4 complex, in reasonable agreement with the experimental findings. It was further confirmed using DFT that the exchange of Pb2+ ions with NH4+ ions is energetically favorable. Because of its high removal efficiency, selectivity, easy synthesis and handling, cost-effectiveness, fast kinetics, high stability in acidic pH and effective adsorption of Pb2+ ions even in the presence of alkali and alkaline metal ions, the APM sorbent can potentially be used to remove toxic Pb2+ ions from aqueous solutions for commercial applications. [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]

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]

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]

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]

In this paper, Cr oxygenated species dispersed on Pt nanowire assemblies (PtCrOX NWs) were successfully prepared for the methanol oxidation reaction by a metal precursor dilution strategy. Notably, the PtCrOX NWs catalyst exhibits excellent performance for electrocatalytic methanol oxidation. Density functional theory results revealed that the doped Cr oxygenated species, which moderated the electronic structure of the Pt atoms, can significantly decrease the free energy of COOH* formation, thus leading to superior methanol oxidation performance. [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]

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]

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]

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 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]

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]

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]

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]

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]

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]

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]

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]

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 development of new, efficient noble-metal-free photocatalysts is of great significance for the photocatalytic hydrogen evolution reaction. Herein, Co9S8 with a hollow polyhedral structure was synthesized by in situ sulfurization of ZIF-67, and subsequently, Co9S8@Ni2P composite photocatalytic materials were prepared by loading Ni2P on the surface of Co9S8 through a solvothermal method based on a morphology regulation strategy. The design of the 3D@0D spatial structure of Co9S8@Ni2P is favorable for the formation of photocatalytic hydrogen evolution active sites. Due to the excellent metal conductivity of Ni2P, Ni2P as a cocatalyst can accelerate the separation of photogenerated electrons from holes in Co9S8, thus providing a large number of available photogenerated electrons for photocatalytic reactions. It is worth mentioning that a Co–P chemical bond is formed between Co9S8 and Ni2P, which plays an active role in the transport of photogenerated electrons. The densities of states of Co9S8 and Ni2P were determined by density functional theory (DFT) calculations. The reduction of the hydrogen evolution overpotential and the formation of efficient charge-carrier transport channels on Co9S8@Ni2P were confirmed by a series of electrochemical and fluorescence tests. This study provides a new idea for the design of highly active noble-metal-free materials for the photocatalytic hydrogen evolution reaction. [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]