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A new fluorescent probe (T2) containing pyrene-hydrazone furan moieties was developed and synthesized through a two-step process and then coated onto filter paper to form a paper-based sensor for TNT detection. The T2 sensor uses photoinduced electron transfer (PET) induced fluorescence quenching to detect TNT. The sensor properties were studied using fluorescence spectra, 1H-NMR titration and density functional theory (DFT) calculations. The reaction time of the T2 paper-based sensor for TNT detection was only five minutes. A smartphone was used as an alternative instrument to detect fluorescence signals and a typical image J-processing application was employed to evaluate the grayscale values of the smartphone-captured photographs. The sensor showed a linear concentration range for TNT detection of between 30–500 μM and a detection limit of 30 μM. The T2 paper-based sensor was found to have high selectivity and sensitivity, and it can successfully detect and image TNT in actual samples. This research demonstrates that a T2 paper-based sensor is a promising alternative for TNT detection owing to its short reaction time, high selectivity, sensitivity, and easy applicability. [ABSTRACT FROM AUTHOR]

We present in this paper the stability of SWCNT hybrid systems with Py molecules. vdW type interactions are therefore the main interaction mechanism between encapsulated molecules and nanotubes, and the simplest model to describe these interactions is the Lennard-Jones potential. We have therefore performed energy minimization calculations on hybrid SWCNTs in a very wide range of diameters and of all chirality using the Lennard-Jones potential. The structure of the carbon nanotube is obtained from the winding of graphene on itself to form a hollow cylinder described by the pair of integers (n, m) entirely determining its structural characteristics, while the optimization of the geometry of the Py molecule is obtained by SIESTA using the exchange–correlation functional LDA. After minimisation, an approach that combines density functional theory, molecular mechanics, bond polarizability model, and spectral moment's method has been used to compute Raman spectra. Two types of vibration modes of SWCNTs attract our attention. Initially, the modifications of the modes of Py after encapsulation will be analyzed. In the following discussion, we examine how the vibrational properties of single-walled carbon nanotubes (SWCNTs) are affected by encapsulation, specifically in relation to the RBM and tangential modes. Our analysis of the Raman active modes supports the notion that the structural integrity of the SWCNTs remains intact and indicates the occurrence of a charge transfer between the Py molecules and SWCNTs. This charge transfer depends on the geometric position of Py in the SWCNT. [ABSTRACT FROM AUTHOR]

The treatment of cancer has always been a challenging problem in the medical community. In this paper, based on density functional theory (DFT), B12N12 nanocage was studied as delivery carriers of sulforaphane (SF) anticancer drug, and the adsorption properties, electronic properties and topological analysis of complexes were calculated. The adsorption energy, solvation energy, electronic and topological properties were calculated by used M06-2X/6-311+G(2d,p), M05-2X/6-31G(p) and B3LYP/6-311G(d,p) theoretical levels, respectively. In addition, the effects of doping and packaging of alkaline earth metal (Be, Mg, Ca) on the related properties were also studied. Doping and packaging metal can improve the transfer characteristics of nanocages by changing the polarity of systems. All calculation results were performed in Gaussian 09 software. The frontier molecular orbital (FMO) and natural bond orbital (NBO) analysis showed that nanocages acting as charge acceptors and drugs as charge donors during the adsorption process. The atoms-in-molecules (AIM) and interaction region indicator (IRI) analysis showed that there were strong polar covalent bonds between drug and nanocages, which enabled drug to be stably adsorbed on nanocages. The solvation effect results showed that acidic conditions were more conducive to drug transport and release. Compared with the original and encapsulated systems, the doping system has better adsorption properties and solvation effect. Moreover, the charge transfer between drug and nanocages in doping system was more frequent and the interaction was stronger. Therefore, our results indicated that the doping nanocages MB11N12 (M = Be, Mg and Ca) were more suitable as the drug carrier system for SF anticancer drug. [ABSTRACT FROM AUTHOR]

The host–guest complexes formed between [9–11]CPPs and C60 were studied extensively due to their excellent photoelectric conversion properties and photochemistry. The drastically increased electron accepting ability of Li+@C60 with respect to C60 may induce strong intermolecular charge transfer interaction with [9–11]CPP. In this paper, a comprehensive computational analysis of the structure, intermolecular interactions, absorption spectra, charge transfer characteristics and nonlinear optical properties of [9–11]CPP⊂C60 and [9–11]CPP⊂Li+@C60 were studied using density functional theory calculations. It was found that the intermolecular binding energies of [10]CPP⊂C60 and [10]CPP⊂Li+@C60 were −47.76 and −60.08 kcal mol−1, which were larger than those of [9, 11]CPP⊂C60 and [9, 11]CPP⊂Li+@C60. Thus, [10]CPP was found to be the most ideal fullerene encapsulator and most suitable for encapsulating C60. In addition, with the increase of the CPP ring size, the second hyperpolarizability (γ) values of [n]CPP⊂C60 increase gradually. In addition, the γ values of [9–11]CPP⊂Li+@C60 were all greater than those of [9–11]CPP⊂C60, indicating that embedding Li+ into fullerene spheres can effectively improve their third-order nonlinear optical responses. [ABSTRACT FROM AUTHOR]

In this paper, the water dissociation abilities of transition metals Cr, Co, Ni, Cu, and surface Cr incorporated into Co, Ni, and Cu matrix were estimated using density functional theory. The calculations indicate that the transition metal matrix can markedly affect the ability of surface Cr to promote H2O dissociation. The barriers of the H2O dissociation step on Cr, Co, Ni, and Cu increase in sequence. After introducing Cr into a transition metal matrix, the H2O dissociation ability of Cr reduces. Compared with pure metals, doping the Co surface with Cr is less favorable for H2O dissociation and introducing Cr onto Ni and Cu surfaces can accelerate the H2O dissociation reaction and Cr–Ni has stronger H2O dissociation ability than Cr–Cu. The electron distribution calculations show that the electron deviation levels from Cr to the metal matrix are a key factor in affecting the H2O dissociation ability of surface Cr, and strong electron deviation is advantageous. The adsorption calculations reveal that the OH-binding energy of catalyst cannot relate to its H2O dissociation ability and follows a rough volcano relationship with its alkaline HER performance. [ABSTRACT FROM AUTHOR]

Sensing nitroaromatic explosives has gained significant attention due to both increased terrorist threats and a need for environmental protection. In this regard, a fluorescent chemosensor, 1-benzyl-3,5-di(thiophen-2-yl)pyrazin-1-ium bromide (BTPyz), was synthesized and characterized via spectroscopic methods. The photophysical properties were investigated using absorption and emission spectral analysis. As a fluorescent chemosensor, BTPyz exhibited a selective response towards 2,4,6-trinitrophenol (TNP) with a detection limit of 11.6 nM and quenching constant (KSV) of 3.8 × 104 M−1. The fluorescence quenching mechanism was attributed to ground-state charge-transfer complex formation and resonance energy transfer, as evident from Uv-visible, fluorescence and NMR spectroscopy, single-crystal XRD studies, and density functional theory calculations. BTPyz was also employed for the contact mode detection of TNP on paper strips. The detection of TNP in real water and soil samples demonstrated BTPyz to be a promising detection tool toward environmental specimens. [ABSTRACT FROM AUTHOR]

In this paper, based on density functional theory (DFT), the adsorption and cracking mechanism of CH3OH on the Cu@CnB8 (n = 24, 40, 88) surface is studied. There are three possible paths of C–H, C–O and O–H for the initial cracking of CH3OH on the surface of Cu@CnB8. In this paper, the adsorption energy of CH3OH and intermediates on the Cu@CnB8 surface is calculated, and the related reaction energy and activation energy under the possible cracking path are calculated. The calculation results show that CH3OH is physically adsorbed on the Cu@CnB8 surface. The main path of CH3OH cracking is CH3OH → CH3O → CH2O → CHO → CO. The activity of CH3OH cracking decreases with the increase of Cu@CnB8 size, that is, the small size Cu@CnB8 can be used as an effective catalyst for the cracking of CH3OH. [ABSTRACT FROM AUTHOR]

Calcite is widely used in many fields. The synthesis of calcite is strongly influenced by solvents and additives. In this paper, the adsorption of water and formic acid molecules on the (104) surface of calcite was systematically studied on the atomic scale using the density functional theory (DFT) method. The results show that both molecules can be adsorbed on the calcite surface by occupying the top position of Ca. The results of differential charge density and the projected crystal orbital Hamiltonian population show that the adsorption is controlled by the charge transfer from the oxygen atom to the surface calcium. Formic acid has a carbonyl oxygen and it plays a greater role in stabilizing the surface than water. Moreover, the adsorption of two molecules can be further stabilized by hydrogen bonds formed between the hydrogen atom in the adsorbed molecules and the oxygen in calcite. This work provides a clear understanding of the stabilization of the calcite surface by adsorbing different molecules and also provides the possibility of tuning the synthesis of calcite by choosing a suitable solvent and additives. [ABSTRACT FROM AUTHOR]

This paper reports fluorescein-linked calixarene-based columnar liquid crystals with a broad temperature range of mesophases. The photophysical and density functional theory (DFT) study suggested good electronic behaviour and reactivity of supramesogens. All the synthesized materials (4a–4d) were characterized by FT-IR, 1HNMR, 13C NMR, MALDI-TOF, and elemental analysis and displayed yellow to orange light emission in the solution, thin films, and solid state. Further, all materials showed aggregation-induced emission (AIE) effect with higher quantum yields. The fluorescein-linked supramolecules broadly stabilized the columnar hexagonal phase and formed self-assembly with higher thermal stability. The substituted alkoxy side chains on the terminal position influenced the mesophase temperature range and thermal stability. All the compounds adopted cone conformation, which was confirmed by experimental and computational studies. Further, these fluorescent materials were used to stain model organism nematodes in solution-state aggregation. [ABSTRACT FROM AUTHOR]

The use of industrial solid waste to produce a cement clinker can not only effectively reduce the consumption of natural resources, but also reduce the pollution of waste. In this paper, the solidification trend of Cr ions in the clinker phases of ordinary Portland cement (OPC) was studied by combining experiments with theoretical simulations. The results from energy dispersive spectrometry, X-ray diffraction, and density functional theory (DFT) simulations suggests that Cr ions will preferentially enter the mineral C4AF by displacing Fe ions. Further analysis of the bond length and bond order, electron density differences and partial density of states suggests that this phenomenon is mainly due to the similar electronic contributions of the host and guest ions. These insights will provide important fundamental guidance for understanding the doping behaviour of chromium ions in an OPC clinker and the utilization of Cr-containing industrial solid waste, thus paving an efficient way for the treatment of Cr-bearing industrial solid waste. [ABSTRACT FROM AUTHOR]

Cocatalysts are usually applied in the photocatalytic water splitting process to accelerate the kinetics of the hydrogen evolution reaction (HER). Specifically, the transition metal nitride (Mo2N) featuring a unique local surface plasmon resonance (LSPR) effect has exhibited great potential to function as a HER cocatalyst. However, the low metallicity of Mo2N hampers its ability to improve charge separation. To address this issue, transition metal atom doping (Co and Cu) engineering was used to modulate the electronic structure of Mo2N nanosheets to achieve a higher electrical conductivity and a lower hydrogen adsorption free energy (‖ΔGH*‖), thereby favoring the HER kinetics. Density functional theory (DFT) calculations and experimental results showed that Co-doping and Cu-doping mainly take place at Mo sites in the crystal structure of Mo2N to form stable structures of Co doped Mo2N (Co–Mo2N) and Cu doped Mo2N (Cu–Mo2N). Compared with pristine Mo2N, both Cu–Mo2N and Co–Mo2N demonstrated a much improved cocatalytic effect over g-C3N4 in promoting charge separation, accelerating HER kinetics and enhancing light absorption. The Co–Mo2N with the highest conductivity and lowest ‖ΔGH*‖ illustrated the best cocatalytic effect, and the H2 production performance (367.8 μmol g−1 h−1) of Co–Mo2N/g-C3N4 achieved was 10 and 5 times higher than those of Mo2N/g-C3N4 and Cu–Mo2N/g-C3N4. This paper provides significant guidance in the design and development of efficient cocatalysts for the HER application. [ABSTRACT FROM AUTHOR]

Carbazole-substituted N-heterocyclic carbene (NHC)–gold complexes have exhibited diverse structural features and interesting thermal properties. The role of the remotely linked carbazole group to mesoionic carbene in gold(I)–NHC complexes has been addressed in this paper. Thus, we have synthesized and characterized neutral gold–mesoionic carbene monomers tagged with carbazole groups. The mononuclear gold(I)–carbene complexes [(L1)AuCl] (1) and [(L2)AuCl] (2), where L1.HI = 1-(naphth-1-yl)-3-methyl-4-(carbazolylmethyl)-1,2,3-triazolium iodide and L2.HI = 1-(mesityl)-3-methyl-4-(carbazolylmethyl)-1,2,3-triazolium iodide, were synthesized and characterized. This new class of complexes exhibited interesting gold–hydrogen bonding. In addition, the thermal properties of 1 and 2 were investigated. Density functional theory (DFT) calculations and natural bond orbital (NBO) analysis were carried out on a model system, [(L′)AuCl] (1A), where L′ = 1-phenyl-4-methyl-carbazole-1,2,3-triazol-ylidene, to realize the bonding situations. The calculated metrics agreed reasonably well with the experimental observations. [ABSTRACT FROM AUTHOR]

In this paper, a novel Schiff base ligand NaHL (NaHL = sodium (S,E)-2-((4-chloro-2-hydroxybenzylidene) amino) propanoate) was designed and synthesized, and three novel complexes with Zn(II) were obtained by a solvent evaporation technique. Single crystal X-ray diffraction indicated that [Zn(L)(H2O)]n1 and [Zn(L)(H2O)]n2 were one-dimensional coordination polymers (CPs) with a helix structure, while [Zn2(L)2(bipy)] 3 was a two-dimensional CP with the participation of an auxiliary ligand. Fluorescence spectra exhibited that 1 and 2 had good fluorescence properties in both solution and solid states, but 3 was basically quenched due to the addition of ancillary ligands in the solid state. Density functional theory (DFT) calculations have been performed to further reveal the intrinsic fluorescence properties and mechanisms of 1 and 2, which demonstrated the chelate fluorescence enhancement effect (CHEF). Moreover, 1 and 2 show selective recognition of NH4+ and HPO42− accompanied by an efficient fluorescence "turn off" phenomenon, and a series of related experiments demonstrate that 1 and 2 were fully quenched through the removal of Zn2+ from the complex and the protonation of the ligand. [ABSTRACT FROM AUTHOR]

In this paper, eight complexes M-1, M-2, M-3 and M-4 (M = Ir or Rh) in the general formula [M(C^N)2(N^N)] (C^N = cyclometalated ligands and N^N = ancillary ligands) are systematically investigated by density functional theory (DFT) and time-dependent DFT methods. With the aim to study the influence of metal centers for nonlinear optical (NLO) responses, the geometrical and electronic structures, first hyperpolarizabilities (βtot) and UV-Vis absorption spectra are investigated in detail. It is found that the βtot values increase 1.8–3.7 times as the metal atom changes from Rh to Ir. Among all the studied complexes, Ir-3 (C^N = 4-chloro-2-phenylquinoline with N^N = 2,9-dimethyl-1,10-phenanthroline) shows the highest βtot value with an amplitude of 2415.4 a.u. computed at the ωB97XD/6-31G+(d)/SDD level, which can be seen as a promising candidate for second-order NLO materials. In addition, the HOMO energy levels increase upon increasing the size of the metal atom, which contributes to a significant reduction in HOMO–LUMO gaps. The βtot values and HOMO–LUMO gaps are in an inverse relationship. Furthermore, tuning the center metals Ir/Rh can be seen as an effective method to modulate the charge transfer degree. We anticipate that this study may serve as a new strategy for the rational design and synthesis of second-order NLO materials. [ABSTRACT FROM AUTHOR]

Designing and discovering negative thermal expansion (NTE) materials is important in precisely controlled thermal expansion devices. In this work, the NTE of a cubic metal fluoride, ReO3-type VF3, was predicted by density functional theory within the quasi-harmonic approximation. These results reveal that cubic VF3 displays a negative thermal expansion behavior below 200 K, and the predicted minimum negative thermal expansion coefficient is approximately −6.4 × 10−6 K−1 at 80 K. The negative thermal expansion was mainly dominated by the prominently negative Grüneisen parameter situated at M(0.5,0.5,0) and R(0.5,0.5,0.5). The underlying mechanism was attributed to the anisotropic F atom vibration, where the amplitude of transverse vibration perpendicular to the V–F–V connection was much larger than that of the vibration along the parallel V–F–V direction. This research provides a good understanding of the relationship between NTE and crystal structure. [ABSTRACT FROM AUTHOR]

Density functional theory (DFT) was used to investigate the adsorption of twenty-four gases (SiH4, H2, Cl2, F2, CF4, CH4, CF2Cl2, N2, CHF3, OCS, N2O, AsH3, CH3Cl, COCl2, C2H2, C2H4, H2Se, H2S, PH3, COF2, CH3F, HCHO, (CH3)2O, and CH3NH2) on B12N12 and Al12N12 nanocages. Most of the studied gases are weakly (strongly) adsorbed on the B12N12 (Al12N12) nanocage. However, AsH3, H2Se, H2S, PH3, CH3F, HCHO, (CH3)2O, and CH3NH2 are strongly adsorbed on the B12N12 nanocage and H2, F2, CF4, CH4, and CF2Cl2 are weakly adsorbed on the Al12N12 nanocage. The most negative-valued molecular electrostatic potential (MESP) minimum (Vmin) corresponds to the electron-rich region (e.g., lone pair and π-bond) in the molecule. An important observation is that the adsorption energies of the gases on the B12N12 and Al12N12 nanocages are well correlated with the MESP Vmin values of the gases. Substantial changes are found in the DFT reactivity indices like chemical potential and hardness of the B12N12 and Al12N12 nanocages, mainly due to the strong gas adsorption. The quantum theory of atoms in molecules analysis suggests the covalent nature of interactions only in the AsH3/B12N12, H2Se/B12N12, H2S/B12N12, and PH3/B12N12 systems. [ABSTRACT FROM AUTHOR]

A novel, one-pot, three-component coupling (3-CCR) reaction of aromatic aldehydes, β-naphthol, and 6-amino-1,3-dimethyl uracil in a deep eutectic solvent (DES) has been developed as a highly efficient and selective method for the expedient synthesis of the densely functionalized 8,10-dimethyl-12-phenyl-8,12-dihydro-9H-benzo[5,6]chromeno[2,3-d]pyrimidine-9,11(10H)-dione framework in synthetically pleasing yield. The devised protocol adeptly harnesses the versatility of DESs, resulting in a straightforward, cost-effective, resilient, and environmentally sustainable synthetic approach. The resulting cascade adduct exhibits noteworthy antiproliferative activity against a variety of cancer cell lines, thereby showing promise as a potential anticancer drug candidate for breast and hepatocellular carcinoma with moderate to good IC50 values. The most potent compounds in the synthesized library, 4m and 4l, exhibit highly potent cytotoxicity against HepG2 and MCF7 cancer cell lines, with notable IC50 values of 46.39 and 28.21 μM, respectively. The present findings are corroborated by computational and molecular docking studies. The density functional theory (DFT) calculations underscore the pivotal role of the naphthyl ring in orchestrating the success of this intricate domino process in delivering the anticipated scaffolds in reasonable yields. [ABSTRACT FROM AUTHOR]

Potassium europium molybdate, KEu(MoO4)2, is an intriguing material known for its efficient luminescence properties attributed to Eu3+ ions and its polymorphic nature. Despite its significance, research on the metastable γ-phase has been limited, with no prior reports on its structure, particle morphology, and luminescence characteristics. In this study, both the stable α-phase and the metastable γ-phase of KEu(MoO4)2 were synthesized using solid-state and hydrothermal reaction methods, and their crystal structures, particle morphologies, and luminescence properties were comprehensively investigated. X-Ray diffraction analysis confirmed the formation of the triclinic α-phase and the orthorhombic γ-phase, with factor analysis results consistent with theoretically optimized structures, facilitating accurate structural determination. Both phases exhibited typical photoluminescence (PL) spectra of Eu3+ ions. However, in the γ-phase, the 5D0 → 7F2 transition appeared as a non-split peak with minimal Stark effect, attributed to differences in structural symmetry between the phases. A red-shift in the PL excitation edge was observed in the α-phase, which was attributed to a narrowed band gap resulting from the broadening of the O-p orbital in the valence band, as indicated by density functional theory (DFT) calculations. Additionally, KEu(MoO4)2 was doped with Y3+ ions to form K(Eu,Y)(MoO4)2, revealing a solid solubility limit of 40% in the α-phase, while the γ-phase displayed no solid solution limit. The estimated critical distance of Eu3+ ions suggested that Eu–Eu interactions contributing to concentration quenching are minimal in the stacking direction but significant in the in-plane direction, operating in the second shell. [ABSTRACT FROM AUTHOR]

A combined density functional theory (DFT) and microkinetic model (MKM) based approach is applied to design Pd-based A3B type bimetallic alloys – Pd3Cu, Pd3Ag and Pd3Au for hydrodechlorination (HDC) reaction of 4-chlorophenol (4-CP). The DFT results predict that the binding energy trend of 4-CP is Pd3Cu (111) [−257 kJ mol−1] > Pd (111) [−165 kJ mol−1] > Pd3Au (111) [−151 kJ mol−1] ≈ Pd3Ag (111) [−151 kJ mol−1]. The adsorbed 4-CP then undergoes C–Cl bond dissociation followed by hydrogenation to form phenol. Of all the surfaces, Pd3Ag (111) exhibits the least activation barrier for Cl dissociation from 4-CP (44 kJ mol−1), followed by Pd3Au (111) (66 kJ mol−1), Pd (111) (71 kJ mol−1) and Pd3Cu (111) (76 kJ mol−1) surfaces. The DFT generated data are utilized to construct an ab initio microkinetic model to calculate the turnover frequencies (TOFs) of 4-CP HDC. The Pd3Ag (111) surface displays the highest TOF, which could be attributed to the ease of Cl dissociation from the 4-CP molecule. However, the low TOF over the Pd3Cu (111) surface could be due to surface poisoning as a result of high 4-CP binding energy on the surface. For the C–Cl bond dissociation step, a positive degree of rate control is observed, which suggests that this step is crucial in ascertaining the HDC rate. [ABSTRACT FROM AUTHOR]

To overcome the limitations of the Fe(II)-activated percarbonate process for ACT removal, this study introduced cysteine as a complexing agent into the Fe(II)/SPC system and enhanced the degradation efficiency of ACT. Investigations were conducted on the effects of pH, temperature, common anions (Cl−, HCO3− and NO3−) in the water column, and humic acid (HA) on the degrading efficiency of the Cys/Fe(II)/SPC system. The results showed that under ideal conditions, 99.9% removal of ACT at 0.05 mM could be achieved. Alkaline environments inhibited ACT degradation, whereas acidic environments promoted it. Electron paramagnetic resonance (EPR) successfully detected ˙OH and O2˙−, but no 1O2 radical signal was detected. Further research was carried out to determine how much ˙OH and O2˙− contributed to the oxidation process. The results showed that both ˙OH and O2˙− contributed to the degradation of the ACT, with ˙OH's contribution being particularly significant. Mass spectrometry analysis was used to determine the structure of the oxidation products. Vulnerable sites in ACT were predicted using density functional theory. Using LC-MS/MS analysis, seven intermediates of the Cys/Fe(II)/SPC degradation of ACT were individually identified. The results showed that the acetylamino group on ACT and the C–N bond on the benzene ring are susceptible to attack by ˙OH. The T.E.S.T. toxicity prediction model was used to predict the toxicity of ACT and its intermediates. The results showed a trend towards reduced acute toxicity and overall developmental toxicity. [ABSTRACT FROM AUTHOR]

The quantitative structure-property relationship (QSPR) of constrained geometry catalysts (CGCs) has been analyzed by combining density functional theory (DFT) and multivariate linear regression (MLR). QSPR models for determining the reaction energy barriers of ethylene and 1-octene and molecular descriptors were established and validated with a testing set. At the initiation stage, the quaternary QSPR models for ethylene and 1-octene feature R² values of 0.90 and 0.82, respectively, while the corresponding leave-one-out Q² values for ethylene and 1-octene are determined to be 0.82 and 0.69. Using the generated QSPR models, the electronic effect was proven to be more critical for determining the energy barriers of ethylene and 1-octene insertion processes. At the propagation stage, the quaternary QSPR models for ethylene and 1-octene feature R² values of 0.97 and 0.96, respectively, while the corresponding leave-one-out Q² values for ethylene and 1-octene are determined to be 0.93. Particularly, the impact of the steric effect on the energy barriers of ethylene and 1-octene insertion is more pronounced. Furthermore, the correlation between the corresponding energy barriers and experimental activities with three series of CGCs was discussed, which revealed that theoretical calculations are consistent with the experimental results. [ABSTRACT FROM AUTHOR]

A metal-free one-pot cascade process involving reduction of nitroarenes, cyclization, and sequential hydrogenation of imines with B2cat2 and water was developed to construct dihydroquinoxalinones and tetrahydroquinoxalines directly from readily available 2-nitroanilines or o-dinitrobenzenes with α-ketoesters and a-diketones. This strategy provides various dihydroquinoxalinones and tetrahydroquinoxalines in good to excellent yields and tolerance to many functional groups. Mechanism studies by control experiments and density functional theory (DFT) calculations show that this cascade procedure involves the deoxygenative reduction of nitroarenes, the Maillard reaction, and hydrogenation to produce dihydroquinoxalinones and tetrahydroquinoxalines. This method aims to reduce the environmental impact while maintaining high yields and selectivity for both nitroarene reduction and the synthesis of dihydroquinoxalinones and tetrahydroquinoxalines. [ABSTRACT FROM AUTHOR]

In this work, density-functional theory (DFT) was used to investigate the geometry and electronic structure of Run(n = 1–6,10) supported on CeO2(110) (Run(n = 1–6,10)/CeO2(110)) and their electrocatalytic properties for the N2 reduction reaction (NRR). The results indicated that there is a strong metal–support interaction between Run and CeO2(110), which leads to large surface distortion and stabilized Run. On Run(n = 1–6,10)/CeO2(110), N2 captured in the end-on mode is thermodynamically more favorable than that captured in the side-on mode; however, the side-on mode can lead to stronger activation of N2 which promotes the following protonation step of N2. For Run(n = 3,5,6)/CeO2(110), the electrochemical NRR prefers to occur via an enzymatic mechanism with limiting potentials of −0.31, −0.53 and −0.66 V. The electrocatalytic activity of Run(n = 1–6,10)/CeO2(110) for the NRR shows a strong size dependence. For Ru3/CeO2(110), it has the lowest absolute value of limiting potential, and with the increase in n (n > 3), the limiting potential becomes more negative. Moreover, Ru3/CeO2(110) shows high selectivity and stability. This study gives valuable insights for designing effective catalysts for the NRR. [ABSTRACT FROM AUTHOR]

Non-acidic hydrogen evolution systems have a low concentration of hydrogen ions, and the H2 evolution reaction (HER) is often limited by the water dissociation step. Preparing catalysts that can accelerate water dissociation is a common method for achieving high-efficiency evolution of hydrogen. In the current work, the performance of a hydrogen evolution system was first improved by introducing CO2 to transform the presence status of H2O. According to density functional theory (DFT) calculations, water reacts with CO2 to produce carbonic acid which can reduce the barrier of adsorbed H generation. Subsequently, under same pH conditions, a constructed dye-sensitized Ni–CO2 system shows an H2 evolution rate 1.5 times higher than that shown by dye-sensitized Ni. This result indicates that transforming the presence status of H2O may be a new strategy for further improving H2 evolution efficiency. [ABSTRACT FROM AUTHOR]

Mastery with regard to the evolution of the chemical form of fission products in the primary circuit is essential for the development and improvement of models, which can predict the release of fission products into the primary loop under normal or accidental operating conditions and analyze the consequences of severe accidents. Here, the chemical forms of fission products in the primary loop of the HTR-PM are predicted by the thermodynamic database method. Furthermore, the microscopic mechanisms of the reactions between radionuclides Cs and I with steam are systematically investigated using density functional theory. The predominant reaction products of Cs + H2O and I + H2O include CsO, CsOH, IO, IOH, and HI. The bond evolution properties are analyzed using the electron localization function, quantum theory of atoms in molecules, bond order density, and mayer bond order. The reaction rate constants are determined utilizing the variational transition state theory. Within the temperature range of the HTR-PM primary circuit (250–750 °C), the reaction rate constant of OIH2 is effectively zero, and the reaction rate constant of HI is higher than that of IOH. The results of the above microscopic calculations are consistent with the macroscopic thermodynamic calculations, and these data serve as valuable ESI for the experiments. [ABSTRACT FROM AUTHOR]

Inhibition of intraerythrocytic iron uptake by plasmodium parasites is a viable alternative antimalarial mode of action to that adopted by artemisinins, since microorganisms require iron for growth and replication, but this has received less research attention. Against this backdrop, an in silico study on bis-thiosemicarbazones (TSCs) with significant antiplasmodial properties as Fe(III)-selective chelators and inhibitors of hemozoin formation is undertaken herein using density functional theory (DFT), molecular docking and molecular dynamics (MD) simulations. From the large contrasts in calculated binding energies for Fe(III) and Fe(II) sequestration in aqueous solution at DSD-BLYP/def2-TZVPD level of theory (−1162.99 to −1187.64 kcal mol−1 and −671.75 to −687.60 kcal mol−1, respectively), the TSCs are potential Fe(III)-selective chelators as desired for chelation therapy. Based on their satisfactory oral bioavailability profiles, the TSCs are found to be adequately drug-like. They are therefore expected to easily penetrate parasitized erythrocytes and inhibit the growth/development of plasmodium parasites by scavenging and externalizing intraerythrocytic ferric iron. Moreover, docking and adsorption studies of these TSCs onto the (001) face of the β-hematin crystal have yielded favorable binding free energies (−9.874 to −11.83 kcal mol−1) and negative adsorption energies (−84.61 to −109.80 kcal mol−1), respectively. The adsorption energies obtained herein are either comparable or more negative than those obtained in previous studies for well-known antimalarial drugs. Therefore, besides Fe(III)–chelation, the antiplasmodial activities of the TSCs studied are also attributable to inhibition of β-hematin/hemozoin formation, which has a cascade effect on plasmodium parasite survival. From our findings, in vitro β-hematin inhibition assays on these TSCs are recommended. [ABSTRACT FROM AUTHOR]

MoSe2 as one graphene-like 2D transition metal selenide has attracted great attention. However, its application for the hydrogen evolution reaction (HER) is still restricted by the poor electrical conductivity and structural restacking. In this work, an excellent electrocatalyst for hydrogen production is developed based on the in situ synthesis of V-doped MoSe2 confined on carbon black nanoparticles (denoted as V-MoSe2/CB) via a sol–gel process. The characterization results show that the carbon black nanoparticles can protect the V-MoSe2 nanosheets from agglomeration, resulting in ultra-thin thickness and short vertical lattice arrays. Meanwhile, density functional theory (DFT) calculations indicate that vanadium doping can optimize the electronic structure of MoSe2. Accordingly, compared to the pure MoSe2, V-MoSe2 and MoSe2/CB electrocatalysts, V-MoSe2/CB exhibits improved electrocatalytic activity with a small overpotential of 166 mV at −10 mA cm−2 and a small Tafel slope of 65 mV dec−1. This work paves a new way for improving the HER performance through synergistic morphology, structure and electronic regulation. [ABSTRACT FROM AUTHOR]

Porphyrins have been widely used in designing photocatalyst systems. However, finding an effective strategy to improve the intrinsic photocatalytic activity of porphyrin molecules remains a challenge. Here, two new porphyrins, meso-tetra(5-carboxyfuryl)porphyrin (H2TCFP) and meso-tetra(5-carboxythienyl)porphyrin (H2TCTP), were successfully synthesized and compared with meso-tetra(m-carboxyphenyl)porphyrin (H2TmCPP), to clarify the influence of the organic unit bridging the carboxyl acid group with the porphine ring on the photocatalytic activity of porphyrin for H2 evolution from water splitting. The H2 evolution rates of 10.8 mmol g−1 h−1 observed for H2TCFP and 9.7 mmol g−1 h−1 for H2TCTP are both larger than 8.0 mmol g−1 h−1 observed for H2TmCTP under optimal conditions. The best photocatalytic activity observed for H2TCFP was investigated through experiments and density functional theory (DFT) calculations and was interpreted in terms of the combined effect of several key factors of the entire photocatalytic process, including the high absorptivity of UV light, high separation efficiency of photogenerated carriers, and low Gibbs energy required for associated water splitting. Meanwhile, the concentration-dependent performance of photocatalytic activity was analyzed and attributed to the aggregation and light-bleaching effect exerted on porphyrins. [ABSTRACT FROM AUTHOR]

Encouraged by the promising performance of C60-graphene single-molecule transistors observed in experiments, two types of Fen/C60-GNR (n = 2 and 4 and GNR = graphene nanoribbon) molecules with Fe atoms sandwiched between the upper and lower GNR layers were designed and their electronic and transport properties were investigated by employing density functional theory (DFT) and nonequilibrium Green's function (NEGF) methods. Adding the Fe atoms induces high spin magnetism in the systems. Within the considered bias, almost all Fe2/C60-GNR devices generate double NDR peaks, and some of the Fen/C60-GNR devices (n = 2 and 4) possess a large peak-to-valley current ratio R = Ipeak/Ivalley (>400), implying potential applications in developing on–off–on/off–on–off current switches. The NDR character originates from the crossing of the frontier molecular orbitals. In addition, these systems show distinct spin-polarized transport characteristics, with up-spin channels displaying higher conductivity than down-spin pathways. The spin filter efficiency (SFE) oscillates up and down as bias is scanned for almost all devices, suggesting the possibility of designing on–off–on/off–on–off current switches as well as up–down spin switches. All these findings provide guidance for exploring single molecular devices with promising properties combined with graphene, fullerenes, and transition metals. [ABSTRACT FROM AUTHOR]

This work explores the characteristics of two-dimensional (2D) titanium carbide (Ti3C2 MXene) and utilizes first-principles study to weigh its potential for supercapacitor applications. Scanning electron microscopy images confirm the layered morphology of the MXene, and energy-dispersive X-ray spectroscopy (EDX) analysis supports the extraction of aluminum from the MAX phase. Fourier-transform infrared (FTIR) spectroscopy confirms the presence of oxygen-based functional groups on the surface of the MXene and X-ray diffraction (XRD) patterns validate its hexagonal crystalline structure. Cyclic voltammetry (CV) analysis reveals the presence of redox peaks, indicating the pseudocapacitive behaviour of the fabricated electrode. Additionally, galvanostatic charge–discharge (GCD) measurements yield a calculated specific capacitance of 370 F g−1. Electrochemical impedance spectroscopy (EIS) substantiates the low impedance resulting from the layered structure via the adequate adsorption/desorption of cations. The utilization of first-principles density functional theory (DFT) calculations reveals the merging of conduction and valence bands, signifying effective conductivity. Both the total and partial density of states cross the Fermi level, indicating a highly efficient charge mobility process. The combination of prominent surface redox reactions and excellent conductivity contributes to the superior specific capacitance of the fabricated electrode. Overall, these results highlight the excellent electrochemical properties of the Ti3C2 MXene electrode, declaring it as a promising candidate for supercapacitor applications. [ABSTRACT FROM AUTHOR]

In this work, the interfacial self-assembly behavior of [1,1′:3′,1′′-terphenyl]-4,4′′-dicarboxylic acid (TDA) and the regulation of the introduced guest molecules (trimesic acid (TMA) and coronene (COR)) on TDA's mono-component system were investigated by scanning tunneling microscopy (STM), and the formation mechanism was investigated by density functional theory (DFT). Newly added TMA molecules destroyed the single-row structure formed by TDA self-assembly and formed a new hexagonal co-assembly structure with TDA molecules. When COR was introduced into this system, the co-assembly structure collapsed and the resulting structure was dependent on the concentration of the COR solution. [ABSTRACT FROM AUTHOR]

With the current food demand, pesticides have become some of the most important compounds to maintain food quality; however, this requires the development of methodologies that allow fast, sensitive, and low-cost screening for these contaminants. Surface-enhanced Raman spectroscopy is an emerging solution since the interaction between the analyte and metallic nanostructures increases the Raman signals, enabling trace detection and a chemical-specific measurement. In this way, the fast detection of contaminants is possible, and further advances may enable portable assays. In this work, SERS substrates with silver nanosheets (AgNSs) on a copper surface were synthesized, producing a strong SERS effect and a reproducible signal intensity from methylene blue probe molecules at an optimal reaction time of 1 min. A quantitative analysis of the pesticide imidacloprid was then performed by applying a PLSR chemometric model, revealing a high linear correlation between the reference values and the predicted values of the pesticide (Rcv2 = 0.9732 and RMSECV = 0.1239). AgNS substrates were used to determine the feasibility of using this methodology for screening imidacloprid in real bee honey samples obtained through QuEChERS extraction, and an average recovery of 75.5% ± 0.08 was obtained. In addition, density functional theory simulations were carried out to elucidate the possible molecular interaction with the SERS surface and to assign the observed vibrational modes of imidacloprid. SERS is thus demonstrated to be an alternative to conventional pesticide detection techniques. [ABSTRACT FROM AUTHOR]

The design of low-cost and high-performance bifunctional catalysts for the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) is of great significance for overall water splitting. Herein, RuNi single atom alloy (SAA) decorated on reduced graphene oxide (RuNi@rGO) was synthesized by a facile strategy for use as a bifunctional HER/OER catalyst. The as-obtained RuNi@rGO catalyst exhibits outstanding electrocatalytic activities with an ultralow overpotential for the HER (15 mV) and the OER (240 mV) at a current density of 10 mA cm−2. Density functional theory (DFT) calculations demonstrate that the introduction of Ru single atoms can evidently change the electron distribution and coordination environment around Ni, and reduce the intermediate's adsorption free energy of RuNi@rGO, thus facilitating the HER/OER catalytic rate. Moreover, when used as the cathode and anode of a two-electrode system, the RuNi@rGO-based water splitting device exhibits a low potential of 1.52 V at a current density of 10 mA cm−2, as well as a high faradaic efficiency almost up to 100%, making RuNi@rGO bifunctional electrocatalysts attractive for energy storage and conversion. [ABSTRACT FROM AUTHOR]

In this paper, the mechanism of the deoxygenation of lignite model compounds in the aqueous phase under a CO atmosphere catalyzed by OH− ions was investigated at the M06-2X/6-311++G(d, p) level. The results revealed that for the deoxygenation of phenol, the activity of the H species follows H˙ > H− > H+, and the reaction of CO with OH− ions under aqueous conditions confirmed that H− is the dominating active species. The study of H− attacking carbon atoms at different positions on phenol indicated that deoxygenation via substitution to form benzene is preferred over hydrogenation via addition. The effect of the active species H− on the deoxygenation of the lignite model compounds phenol, benzenediols, and benzenetriols was also examined. This study provides valuable information for future research on lignite deoxygenation. [ABSTRACT FROM AUTHOR]

Inspired by the reference R with the IUPAC name ((Z)-2-(aminomethyl)-3-(5-((3-methyl-5-(7-(4-methyl-5-(5,10,15-trimethyl-10,15-dihydro-5H-diindolo[3,2-a:3′,2′-c]carbazol-3-yl)thiophen-2-yl)benzo[c][1,2,5]thiadiazol-4-yl)thiophen-2-yl)ethynyl)furan-2-yl)acrylic acid)), six new organic (D–π–A) dyes for dye-sensitized solar cell (DSSC) applications have been designed. The designed molecules have an electron donor (D), triazatruxene, connected through different π-bridges and an electron acceptor (A), 2-cyanoacrylic acid. The key parameters of the optoelectronic and photoelectric performances were computed by density functional theory (DFT) and time-dependent density functional theory (TD-DFT). Compared to the original dye R, the designed compounds have a higher light harvesting ability with an absorption spectrum that appeared around the infrared region. The maximum absorption wavelength shifted to red from 78 nm to 148 nm, and the light-harvesting efficiency (LHE) curve broadened in the visible region and excellent electron injection efficiency was observed. All these contribute to better short-circuit current density (JSC) and power conversion efficiency (PCE). The results obtained through the global evaluation model for the reference dye R were JSC = 19.21 mA cm−2, VOC = 0.838 V, and PCE = 13.92%. These values are closer to the experimental results (JSC = 19.74 mA cm−2, VOC = 0.957 V, and PCE = 13.4%). The Tat-2 dye achieved a PCE of 23.75%. Therefore, it can be considered a candidate dye for high-yield DSSCs. [ABSTRACT FROM AUTHOR]

This paper aims to investigate the electrochromic properties of tricarbonyl rhenium complexes. Using 4,7-diphenylphenanthroline (L1) and 4,7-di(4-substituted)-1,10-phenanthroline (L2–L5) as bidentate ligands, a series of tricarbonyl rhenium complexes, fac-Re(CO)3(Lx)Cl (x = 1–5), were synthesized and characterized by infrared spectroscopy, 1H NMR, 13C NMR, and high resolution mass spectrometry. Their stereochemistry was investigated by single crystal X-ray diffraction. Theoretical highest occupied molecular orbital and lowest unoccupied molecular orbital charge distributions of fac-Re(CO)3(Lx)Cl were calculated by density functional theory calculations. Their electrochemical and electrochromic properties were studied by cyclic voltammetry, UV-vis spectroscopy and chronoamperometry. All fac-Re(CO)3(Lx)Cl complexes underwent a quasi-reversible reduction–oxidation process and an anodic peak at 1.3 V vs. Ag/Ag+. Electrochromic devices based on fac-Re(CO)3(Lx)Cl exhibited good electrochromic performance such as an obvious change in color from bleached yellow state to colored green state (a challenging electrochromic color), rapid response time of less than 3 s, moderate optical contrast and coloration efficiency, and good switching stability (fac-Re(CO)3(L2)Cl retained 95.2% of its initial optical contrast after 2400 electrochromic switching cycles). The fac-Re(CO)3(L2)Cl with an electron-donating group (–OCH3) at its para-position exhibited better performance including good switching stability, a higher optical contrast and a significant change in color than the unsubstituted, –CH3 substituted, –COOCH3 substituted and Br-substituted analogues. [ABSTRACT FROM AUTHOR]

The electrocatalytic CO2 reduction reaction (CO2RR) offers a fascinating approach to converting CO2 into valuable chemical feedstocks. Up to now, the development of highly efficient electrocatalysts has been a significant bottleneck in this field. In this study, employing density functional theory (DFT) calculations, we design a range of stable two-dimensional (2D) metalloporphyrin organic frameworks (TM-PMOFs, TM = Fe, Co, Ni, Cu, Zn, Ru, Rh, Pd, and Ag, respectively) built by copper clusters and metalloporphyrin (TM-TCPP), whose CO2RR performance is studied in detail. Among them, the 2D cobaltporphyrin-based organic framework (Co-PMOF) is identified to be the best CO2RR electrocatalyst on account of its low limiting potential (−0.53 V), whose enhanced electrocatalytic performance can be attributed to the presence of numerous active sites on both sides of its 2D framework, as well as the synergistic effect between copper clusters and cobaltporphyrins in facilitating CO2 reduction. These findings provide valuable insights and encourage further experimental research on metallic 2D PMOF materials for CO2 electrochemical reduction. [ABSTRACT FROM AUTHOR]

Three chitosan ionic liquid type Schiff bases (CS-IL-SBs) were synthesized by grafting three aldehydes (vanillin, cinnamaldehyde, and pyridine-4-carboxaldehyde) on CS-IL (chitosan grafted with p-toluene sulfonic acid) through a Schiff base reaction. Thermogravimetric analysis indicated that the thermal stability of CS was enhanced by the modification of IL and Schiff base groups. All CS-IL-SBs present a non-crystalline structure as analyzed using X-ray diffraction technique and have a positively charged surface in solution for improved dispersion stability as analyzed using zeta potential testing. A corrosion inhibition performance investigation using electrochemical and mass loss methods was undertaken, which were supported with surface analysis and computational studies. All the CS-IL-SBs act as effective corrosion inhibitors obeying Langmuir adsorption isotherm containing both chemisorption and physisorption for N80 steel in 15% HCl solution. Among them, CS-IL-Vin (grafted by vanillin) exhibits a maximum inhibition efficiency of 83.66% at 400 mg L−1. The analysis of the corroded metal surface via scanning electron microscopy depicts a considerably smooth morphology in the presence of adsorbed CS-IL-SBs. Contact angle tests indicated that the water-repellent ability of the metal surface was increased by the addition of CS-IL-SBs. Density functional theory calculations indicated that the active regions of CS-IL-SBs are mainly distributed in –SO3−, benzene rings, and Schiff base groups. Molecular dynamics simulations show that CS-IL-SBs are parallelly adsorbed on the metal surface to form a stable protective film. CS-IL-Vin shows the best performance among the three CS-IL-SBs, which was selected to be compounded with aided inhibitors with different electrical properties. When CS-IL-Vin was compounded with negatively charged 3-carboxybenzene sulfonate in a ratio of 1 : 3, corrosion inhibition efficiency was the highest, reaching 93.45%. [ABSTRACT FROM AUTHOR]

Rapid detection of diseases depends on the development of sensors that can readily bind to the analyte of interest in a cost effective and facile manner. In this work, a Salen-type Schiff base colorimetric as well as fluorimetric sensor for L -cysteine is synthesized through a facile methodology, with its structure comprehensively characterized via single-crystal XRD measurements (SCXRD). The purity of the sensor is one of its key aspects, which is unequivocally established here by the crystal data. This probe effectively demonstrates its aptitude for selective recognition of biologically significant molecule, L -cysteine, employing a synergistic combination of static and dynamic fluorescence quenching mechanisms. Employing spectroscopic analyses and density functional theory (DFT) investigations, it has been conclusively ascertained that the nonradiative energy transfer from donor to acceptor occurs not via PET, but rather through a FRET mechanism. The probe exhibits excellent detection stability with a response time under 2 minutes, complemented by a remarkably low detection limit of 1.52 × 10−9 M. The benchmarking studies highlight the proposed sensor's purity (achieved through single crystal isolation), superior nanomolar detection limit, and ease of preparation, making it a strong candidate for upscaling and commercial applications. [ABSTRACT FROM AUTHOR]

Nanomaterials synergy in a binary system offers a great opportunity for the development of high-performance electrode material for Lithium-ion batteries (LiBs). So far SnS/Ni3S4 binary sulfides are scarcely investigated as an anode for LIBs. In this work, to intrinsically enhance the kinetics of SnS, SnS/Ni3S4 (SN-x) binary sulfides were synthesized by introducing nickel sulfide with different stoichiometric ratios (0.5, 1, 2, and 3). The developed electrode (SN-2) delivers an initial discharge capacity of 2567 mA h g−1 and a high reversible capacity of 360 mA h g−1 at a current rate of 300 mA g−1 after 180 cycles with a Coulombic efficiency of over 97%. The electrochemical impedance spectroscopy (EIS) and density functional theory (DFT) confirm the improved kinetics of the SN-2 electrode as compared to other electrodes. The significantly enhanced performance of the SN-2 electrode can be attributed to the addition of an optimized amount of Ni3S4, synergistic effects between SnS and Ni3S4, generation of more active sites and structural integrity. This work suggests that the prepared SnS/Ni3S4 binary sulfides exhibit great promise for the development of efficient energy storage devices. [ABSTRACT FROM AUTHOR]

Graphene derivatives have undergone extensive scrutiny concerning their sensing properties with diverse gaseous analytes, and graphene oxide (GO) has gained significant momentum owing to its exceptional sensing capabilities. However, there remains a challenge concerning the detection of selective toxic chemicals, especially from polyurethane industries, such as phosgene (PhG), methyl isocyanate (MIC), chloroform (TCM), and hydrochloric acid (HCl) that pose serious threats to human health. Extended exposure to these volatile organic compounds (VOCs) can cause severe respiratory distress, leading to pulmonary edema. Hence, the early detection of these harmful gases is of utmost importance to maintain a safe working environment in polyurethane and pesticide industries. Therefore, here we explore the potential efficacy of GO for detecting these VOCs using density functional theory calculations. Our results reveal that HCl binds strongly with GO due to its greater charge transfer character. The change in electrical conductivity was correlated to binding efficacy and the recovery time of the GO sensor was evaluated while varying thermal treatment. Among the VOCs, PhG tends to show a minimum recovery time of ∼51 ns at 300 K. Overall results suggest that GO shows great promise for the detection of these toxic VOCs. Our study not only fills a knowledge gap but also paves the way for utilizing GO-based sensors in environmental monitoring and safety systems, creating new opportunities for practical applications. [ABSTRACT FROM AUTHOR]

Ti3C2Tx, as some of the typical MXenes, exhibit great potential for application in rechargeable batteries due to its high conductivity, low ionic diffusion resistance, adjustable layer spacing, and surface modifiability. However, several challenges hinder its practical value, including severe self-stacking, low capacity, and unsatisfactory durability, particularly when accommodating large sodium ions. To address these issues, we have designed a SnS2@Ti3C2Tx sandwich structure with S vacancies through heterojunction engineering. Anchoring SnS2 to Ti3C2Txvia S–Ti–C bonds, this interlocking cooperative heterostructure not only mitigates Ti3C2Tx self-stacking but also exposes a significant number of active sites on the surface. Consequently, it improves the intercalation pseudocapacitance ratio, resolves the reaction kinetic hysteresis caused by the challenging removal of sodium ions, and prevents structural collapse resulting from the volume effect in SnS2. Moreover, the S vacancies effectively enhance the adsorption capacity of Na+, providing additional active sites for their adsorption. Density functional theory calculations demonstrate increased adsorption energy and reduced diffusion energy of sodium ions, thereby improving the sodium storage performance of the materials. The SnS2@Ti3C2Tx heterojunction exhibits an impressive reversible capacity of 225 mA h g−1 at 100 mA g−1, with 82% capacity retention after 1000 cycles. Furthermore, even at 500 mA g−1, a capacity of 122 mA h g−1 can still be achieved after 1000 cycles. Consequently, this research offers novel insights for future exploration in the development of anode materials for ion batteries. [ABSTRACT FROM AUTHOR]

In this study, the performance of predicting fluorescence properties using 11 density functional theory (DFT) functionals was evaluated through a comparison with experimental results of 30 coumarin derivatives. The results revealed that there was no significant difference in the predictive performance of maximum emission wavelengths (MEWs) when using the optimized geometries obtained with the PBE0 functional compared to the other studied functionals. The global hybrid functionals with a small constant fraction of HF exchange (B3LYP, PBE0, M06), double-hybrid functionals (APDF and PW6B9D3), global hybrid functionals with a large constant fraction of HF exchange (M06-2X), and long-range correction functionals (CAM-B3LYP and ωB97X-D) exhibited good predictive ability. The linear relationship coefficient (R) values, between the experimental and calculated MEWs, ranked in the strong linear correlation group. Among them, the functionals B3LYP, PBE0, M06, APDF, and PW6B9D3 yielded the best mean signed error (MSE), mean absolute error (MAE), and root mean square error (RMSE) values. The values (MSE, MAE, RMSE) for the B3LYP, PBE0, M06, APDF, and PW6B9D3 functionals in nanometers (nm) were as follows: (−47, 53, 58), (−59, 61, 66), (−56, 58, 63), (−55, 59, 64), and (−58, 59, 65), respectively. In electronvolts (eV), the values were: (0.34, 0.37, 0.41), (0.44, 0.45, 0.49), (0.41, 0.42, 0.46), (0.41, 0.42, 0.46), and (0.43, 0.43, 0.47), respectively. The pure density functionals (PBE and BP86) and LC-ωPBE exhibited poor predictive ability, with a linear relationship coefficient (R) only ranking in the medium linear correlation group. To enhance prediction accuracy, the corrected calculated MEWs, based on the linear correlation between the calculated and experimental MEWs, were determined. This correction resulted in substantially reduced values for the corrected statistical parameters (MSEcor, MAEcor, and RMSEcor) when compared to the uncorrected values. Importantly, this correction also minimized the variation in prediction performance among different DFT functionals, providing users with greater flexibility in selecting the most suitable DFT functional for their specific needs. [ABSTRACT FROM AUTHOR]

Black phosphorene (BP) is a metal-free two-dimensional photocatalyst with potential for visible-light-driven photocatalytic H2 evolution. However, its inert basal plane toward the HER hinders its practical application. To overcome this problem, we design a novel nonprecious metal–nonmetal co-doping method of BP to activate its inert basal plane and improve photocatalytic HER performance. Through density functional theory (DFT) calculations, we systematically investigate the photocatalytic performance of nonprecious metal and nonmetal co-doped BPs. Our results show that V–N co-doped BP exhibits excellent thermodynamic stability, suitable band structure, improved carrier separation, superior adsorption and dissociation energies and enhanced visible-light absorption coefficient. Importantly, V–N co-doping successfully activates the inert basal plane of BP, allowing it to drive the HER under illumination (ΔGH = −0.12 eV). This study highlights the potential of nonprecious metal–nonmetal co-doping to enhance the photocatalytic activity of BP, providing invaluable insights for advancing the field of co-doped BP in photocatalysis. [ABSTRACT FROM AUTHOR]

Bimetallic sandwich complexes based on the borazocine (B4N4H8) ligand have been studied using density functional theory (DFT). The studied Ca–Ca covalent bond length agrees well with the experimental Ca2 bond length. For the studied complexes, the non-nuclear attractor (NNA) is found at the Ca–Ca bond of K2(B4N4H8)2Ca2 and Na2(B4N4H8)2Ca2. The negative Laplacian at the NNA is noticed for these two complexes, indicating that these complexes are electrides. This study for the first time reports the electride complexes based on the B4N4H8 ligand. Interestingly, upon asymmetric doping with Na and K, no NNA point is found for the complex NaK(B4N4H8)2Ca2, indicating that this complex is not an electride. Our study points out one of the fascinating outcomes that asymmetric doping can affect the occurrence of the NNA in a system. The complex Na2(B4N4H8)2Ca2 exhibits the highest second hyperpolarizability value of 2.2 × 106 au at the ωB97XD/6-311++G(3df,3pd) level among the studied sandwich complexes. [ABSTRACT FROM AUTHOR]

We present a density functional theory study to characterize the possible mechanisms and origins of regio- and stereoselectivities of N-heterocyclic carbene (NHC)-catalyzed reactions of 2-bromoenals with thioamides leading to the formation of 1,3-thiazin-4-ones. According to DFT results, the energetically favorable mechanism involves the following elementary steps: formation of a Breslow intermediate via coordination of the NHC to 2-bromoenal followed by 1,2-proton transfer. Debromination followed by 1,3-proton transfer generates the α,β-unsaturated acylazolium intermediate, which further undergoes thia-Michael addition to thioamide forming the enolate intermediate. Subsequent 1,5-proton transfer and intramolecular cyclization give the six-membered ring intermediate, which upon elimination of NHC leads to the formation of 1,3-thiazin-4-one. The thia-Michael addition step was identified as the regio- and stereoselectivity-determining step, affording the S-configurational product preferentially, in agreement with previous experimental observations. According to NCI analysis, the stronger non-covalent interactions such as CH⋯π, LP⋯π and π⋯π interactions lead to the lower energy of the transition state that corresponds to the major stereoisomer of 1,3-thiazin-4-one. [ABSTRACT FROM AUTHOR]

Two luminescent Re(I) complexes, namely mononuclear fac-[ReCl(CO)3(TT-Py)] (1) and hexanuclear [{Re(μ-Cl)(CO)3(μ-TT-Py)}{Re2(μ-Cl)2(CO)6}]2 (2), were isolated in high yields by a one-pot reaction between [ReCl(CO)5] and different amounts of nitrogen-rich 2-pyridine cyclic triimidazole (TT-Py), which acts as a chelating ligand in both derivatives. The metallo-supramolecular cyclic structure of 2, which can be described as a metallacycle in which two mononuclear units of 1 act as bridging ligands towards two "Re2(μ-Cl)2(CO)6" fragments, was confirmed by single-crystal X-ray diffraction analysis. Both complexes were fully characterized in solution by 1D and 2D multinuclear NMR spectroscopy. 1 and 2 exhibit photoluminescence at room temperature in solution, with a broad unstructured emission in the 530–570 nm range. The nature of the excited states involved in the electronic absorption spectrum of 1 was ascertained by a combined density functional theory and time-dependent density functional theory (TD-DFT) study. Both compounds exhibit strong aggregation induced emission enhancement (AIEE), which is more pronounced for 2 leading to a solid state photoluminescence quantum yield of 2.5% that is one of the highest values ever reported for Re(I) polynuclear metallacycles so far. The versatility of TT-Py to adopt variegated coordination modes, previously observed for Cu(I) and Cu(II) derivatives, is confirmed supporting further use of this ligand to obtain new and peculiar emissive mono-, polynuclear and extended coordination systems. [ABSTRACT FROM AUTHOR]

Covalent triazine frameworks (CTFs) involving donor-π bridge-acceptor (D–π–A) motifs with the electron-withdrawing triazine unit as the acceptor have been regarded as one of the most promising materials for photocatalytic water splitting. The intrinsic features of π-bridges play a critical role in tailoring the polymer properties as well as the photocatalytic performance. Introducing suitable conjugated units as the π-bridge is expected to effectively tune the electronic structure of the resultant D–π–A CTFs and facilitate photo-generated charge separation. However, systematic studies on how different π-bridges would influence the photoelectronic properties of D–π–A type CTFs are still limited. Herein, three types of CTFs with well-defined D–π–A structures named Ben-CTF, BenT-CTF and BenP-CTF were synthesized to investigate the effects of different π-bridges (benzene, thiophene and pyridine units) on the performance of photocatalytic water splitting for hydrogen production. Comprehensive experiments and density functional theory (DFT) calculations revealed that BenP-CTF with the pyridine unit as the π-bridge exhibited superior charge migration ability and higher photocatalytic hydrogen evolution reaction (HER) rates compared to the other CTFs. This work may provide a reference for the rational design and controllable synthesis of CTF materials for efficient photocatalysis. [ABSTRACT FROM AUTHOR]

Density functional theory (DFT) calculations have been carried out to investigate two synthesized iridium(III) complexes with substituted Phbd (1-phenyl-2-(pyridin-2-yl)-1H-benzo[d]imidazole) and Crbd (9-(4-(2-(pyridin-2-yl)-1H-benzo[d]imidazol-1-yl)phenyl)-9H-carbazole) as ancillary ligands. The aim of this paper is to study the effect of the substituent on the geometrical structures, electronic and second-order nonlinear optical (NLO) properties, and UV-vis absorption spectra. It is found that the first hyperpolarizabilities can be easily modulated by the introduction of Phbd and Crbd units. The complex with Phbd possesses larger first hyperpolarizability values compared to the complex with Crbd as an ancillary ligand. Significantly, the changes in the first hyperpolarizabilities can be qualitatively explained by means of the charge transfer pattern. It is anticipated that the theoretical investigation of these iridium(III) complexes will be helpful for designing high performance and versatile NLO materials. [ABSTRACT FROM AUTHOR]

Nitrile-functionalized anticancer drugs have drawn wide attention. However, the water solubility and side-effects of the drugs reduce their effectiveness in cancer therapy. In this paper, three novel para-, meta- and ortho-linked nitrile-containing water solubility copper(II) porphyrin complexes have been synthesized. Then the relationship between the structure and anticancer performance of the three complexes were investigated. When the complexes have an effect on the cancer cells (A549, H1975, HepG2 and T47D) and normal cell (Hs578 Bst), they demonstrate effective anticancer activity and biocompatibility; the para-nitrile functionalized complex p-CuP can selectively act on H1975 cells, with the lowest IC50 (6.09 μM); the anticancer effect of water-soluble porphyrin ligands (p-L , m-L and o-L) is augmented by coordinate to copper ion(II). Furthermore, DNA binding and flow cytometry methods were applied to research their mechanism, and the results show that these complexes could intercalate DNA and the effect of p-CuP is the best, so there is DNA binding in the anticancer mechanism, also accompanied by mitochondrial dysfunction and arresting cell cycle. In addition, Density Functional Theory (DFT) calculation analyses were carried out for the cationic porphyrin ligands and complexes, using the method with a B3LYP level of theory with the 6-31G(d) and LanL2DZ basis sets, which further proved the biological activities of the target compounds. [ABSTRACT FROM AUTHOR]