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New heteroleptic iridium(III) nitro complexes derived from fac-[Ir(NO2)3(H2O)3]
摘要： An aqueous solution of fac-[Ir(H2O)3(NO2)3] (1) was utilized as a starting material for preparation of the new heteroleptic iridium complex [Ir(H2O)(bpy)(NO2)3] (2). From alkaline solutions of 2, the salt Na[Ir(OH)(NO2)3(bpy)]·2H2O was isolated and its structure was determined by X-ray structure analysis. Structures of new compounds 2 and 3 as well as the parent complex 1 was characterized using multinuclear magnetic resonance spectroscopy and mass spectrometry. The structures of parent fac-[Ir(H2O)3(NO2)3] and complexes 2 and 3 were probed by employing density functional theory (DFT) calculations.
关键词： Nitrocomplexes,Iridium,DFT,NMR,Aquacomplexes,X-ray structure
更新于2025-09-23 15:23:52
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Prediction of Structural, Vibrational and Nonlinear Optical Properties of Small Organic Conjugated Molecules Derived From Pyridine
摘要： Nonlinear optical (NLO) effects of organic materials are caused by delocalized electrons and large polarization in molecules. In the present work, theoretical study by using the Density Functional Theory (DFT) at B3LYP/6-311G(d,p) level of theory on three types of pyridine derivates 2,6-dimethoxy-3,5-dinitropyridine (M1), 2-methoxy-3-nitropyridine (M2) and 2-methoxy-5-nitropyridine (M3) is reported. The nuclear magnetic resonance (1H- and 13C-NMR) chemical shifts of the title compounds were calculated using the Gauge Independent Atomic Orbital (GIAO) method and compared to the observed results. Both infrared absorption and Raman are complementary to provide characteristic fundamental vibrations that are necessary for the identification of the molecular structures. Electronic properties such as frontier molecular orbital (HOMO, LUMO), ionization potential (IPad) and electronic affinity (EAad) were determined to get better insight into the molecular properties. Using the Time-Dependent Density Functional Theory (TD-DFT), electronic absorption spectra have been predicted and closely matching the experimental findings. The natural bonding orbital (NBO) calculations were performed in order to elucidate various second order interactions in between the filled and vacant orbitals which are a measure of the intermolecular as well as the delocalization within the molecule. In addition, we have demonstrated that these molecular systems have large first static hyperpolarizabilities and may have potential applications in the development of NLO materials.
关键词： NLO properties,Electronic properties,DFT,Optical spectra,NBO
更新于2025-09-23 15:23:52
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A comparative ab initio study of the structural, mechanical, electronic and optical behaviors of ZnO:Ni thin films with nanometer scale
摘要： The electronic and optical properties of undoped and Ni–doped ZnO thin films with nanometer scale have been studied in the wurtzite phase, by first–principle approach. Density functional theory has been employed to calculate the fundamental properties of the films using full–potential linearized augmented plane–wave method. Ni doping was found to reduce the bandgap value of the material. Additionally, DOS effective mass of the electrons was evaluated. It was revealed that the effective mass of the electrons at the bottom of conduction band increased with Ni doping. Decrease of reflectance for thin films with nanometer scale in the UV–vis region was observed. The substitution by Ni decreased the intensity of the peaks, and a red shift was observed in the absorption peak. Moreover, the static dielectric constant, and static refractive index decreased with Ni content. Energy loss function of the modeled compounds was also evaluated. All calculated parameters were compared with the available experimental and other theoretical results.
关键词： DFT,band structure,structural properties,electronic behaviors,optical properties,ZnO:Ni thin film
更新于2025-09-23 15:23:52
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Visible Light Driven Hydrogen Evolution by Molecular Nickel Catalysts with Time-Resolved Spectroscopic and DFT Insights
摘要： Hydrogen (H2) is a clean fuel that can potentially be a future solution for the storage of intermittent renewable energy. However, current H2 production is mainly dominated by the energy intensive steam reforming reaction, which consumes a fossil fuel, methane, and emits copious amounts of carbon dioxide as one of the byproducts. To address this challenge, we report a molecular catalyst that produces H2 from aqueous solutions, is composed of affordable, earth-abundant elements such as nickel, and has been incorporated into a system driven by visible light. Under optimized conditions, we observe a turnover number of 3880, among the best for photocatalytic H2 evolution with nickel complexes from water?methanol solutions. Through nanosecond transient absorption, electron paramagnetic resonance, and UV?vis spectroscopic measurements, and supported by density functional theory calculations, we report a detailed study of this photocatalytic H2 evolution cycle. We demonstrate that a one-electron reduced, predominantly ligand-centered, reactive Ni intermediate can be accessed under visible light irradiation using triethylamine as the sacrificial electron donor and reductive quencher of the initial photosensitizer excited state. In addition, the computational calculations suggest that the second coordination sphere ether arms can enhance the catalytic activity by promoting proton relay, similar to the mechanism among [FeFe] hydrogenases in nature. Our study can form the basis for future development of H2 evolution molecular catalysts that incorporate both ligand redox noninnocence and alternative second coordination sphere effects in artificial photosynthetic systems driven by visible light.
关键词： Proton relay,Second coordination sphere,DFT calculations,Time-resolved spectroscopy,Visible light photocatalysis,Hydrogen evolution,Molecular nickel catalysts
更新于2025-09-23 15:23:52
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Molecular Identification, Bond Order Discrimination, and Apparent Intermolecular Features in Atomic Force Microscopy Studied with a Charge Density Based Method
摘要： We introduce an efficient method to simulate high-resolution atomic force microscopy (HR-AFM) images with CO probes. Our model explicitly takes into account the charge densities of the sample and the probe for the calculation of the short-range (SR) interaction and retains ab initio accuracy with only two parameters, that are essentially universal, independent of the number of chemical species and the complexity of the bonding topology. The application to molecular images shows a strong dependence on the stoichiometry and bonding configuration that precludes the chemical identification of individual atoms based on local force–distance curves. However, we have identified features in the 2D images and 3D force maps that reflect the highly anisotropic spatial decay of the molecular charge density and provide a way towards molecular identification. The model treats SR and electrostatics interactions on an equal footing and correctly pinpoints the Pauli repulsion as the underlying interaction responsible for the bond order discrimination in C60. Finally, we settle the controversy regarding the origin of the intermolecular features, discarding the effect of the charge redistribution associated with the H bonds, and linking them with the overlap of the wave functions of the atoms that constitute the bond. This overlap creates saddle regions in the potential energy landscape that are sensed by the probe.
关键词： tip functionalization,DFT,chemical identification,CO molecule,hydrogen bonds,non–contact atomic force microscopy,bond order
更新于2025-09-23 15:23:52
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Using first principles calculations to interpret XANES experiments: Extracting the Size-dependence of the (<i>p, T</i>) phase diagram of sub-nanometer Cu clusters in an O<sub>2</sub> environment
摘要： We have used ab initio density functional theory together with ab initio atomistic thermodynamics, and in situ X-ray absorption near edge spectroscopy (XANES) experiments, to study the oxidation of sub-nanometer clusters of CunOx supported on a hydroxylated amorphous alumina substrate in an O2-rich environment. We obtain (p, T) phase diagrams; these differ notably for the nanoclusters compared to the bulk. Both theory and experiment suggest that in the presence of oxygen, the cluster will oxidize from its elemental state to the oxidized state as temperature decreases. We obtain a clear trend for the transition Cun→ CunOn/2: we see that smaller the cluster, greater is the tendency toward oxidation. However, we do not see a monotonic size-dependent trend for the transition CunOn/2→ CunOn. We suggest that theoretically computed Bader charges constitute a simple yet quantitative way to align experimental measures of XANES edges with theoretical calculations, so as to yield oxidation states for nanoclusters. Our results have important implications for the use of small clusters in fields such as nanocatalysis and nanomedicine.
关键词： cluster,DFT,XANES,copper,oxidation
更新于2025-09-23 15:23:52
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Towards the design of optically active thiophene S-oxides using quantum chemistry
摘要： The importance of axially chiral biaryls has risen steeply in the recent decades. This structural motif proved to be successful in catalytic asymmetric synthesis and the configuration of the biaryl axis is decisive for biological activity. A new approach for the atroposelective synthesis of biaryls would be through a cycloaddition between an enantiopure phenyl-substituted thiophene S-oxide and an alkyne. Importantly, the chiral center of the thiophene S-oxide needs to be stable enough to avoid pyramidal inversion during the cycloaddition. Since the racemization of thiophene monoxides has been scarcely investigated so far, we perform a thorough quantum chemical study on the inversion barriers of a large number of chiral thiophene S-oxide derivatives. Our main goal is to identify substitution patterns leading to stable atropisomers at room temperature. Appealingly, the role of the stereoelectronic effects and position of the substituents as well as the importance of aromaticity on the pyramidal inversion barrier is elucidated for the first time.
关键词： thiophene sulfoxides,axial chirality,DFT,enantiomerization,aromaticity
更新于2025-09-23 15:23:52
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Importance of electron correlations in understanding photoelectron spectroscopy and Weyl character of
摘要： We study the role of electron correlations in the presumed type-II Weyl semimetallic candidate γ-MoTe2 by employing density functional theory (DFT) where the on-site Coulomb repulsion (Hubbard U) for the Mo 4d states is included within the DFT+U scheme. We show that pure DFT calculations fail to describe important features of the light-polarization dependence of the angular resolved photoemission intensity which can be accounted for by including the role of the Hubbard U. At the same time, while pure DFT calculations cannot explain the angular dependence of the Fermi surface as revealed by quantum oscillation experiments (a fact which had raised doubt about the presence of the Weyl physics in γ-MoTe2), inclusion of such on-site Coulomb repulsion can. We find that while the number of Weyl points (WPs) and their position in the Brillouin zone change as a function of U, a pair of such WPs very close to the Fermi level survive the inclusion of these important corrections. Our calculations suggest that the Fermi surface of γ-MoTe2 is in the vicinity of a correlations-induced Lifshitz transition, which can be probed experimentally and its interplay with the Weyl physics might be intriguing.
关键词： electron correlations,Lifshitz transition,angular resolved photoemission,MoTe2,DFT+U,Hubbard U,quantum oscillation,Weyl semimetal,photoelectron spectroscopy
更新于2025-09-23 15:23:52
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A new non-centrosymmetric Chlorobismuthate(III) hybrid material: Crystal structure, optical properties and antibacterial study
摘要： As part of our interest in organic-inorganic metallate complexes, we had prepared a novel non-centrosymmetric chlorobismuthate (III) compound with the chemical formula (C6H7NCl)3 [BiCl6]$H2O, by slow evaporation method at room temperature. It was characterized by single crystal X-ray diffraction (SCXRD), X-ray powder diffraction (PXRD), spectroscopic measurements, thermal study, Hirshfeld surface analysis, DFT investigation, and antimicrobial activity. A preliminary SCXRD structural analysis revealed that the compound crystallizes in the Orthorhombic system (P212121 space group) with the following unit cell parameters a ? 7.3432 (1) ?, b ? 13.8257 (2) ? and c ? 28.2140 (5) ? with Z ? 4 and V ? 2864.42 (8) ?3. The examination of the structure shows that its atomic arrangement can be described as inorganic [BiCl6]3- units isolated from each other by the organic cations and the co-crystallized water molecules. The cohesion between these entities is performed via the NeH/Cl, NeH/O, CeH/O, CeH/Cl, and OeH/Cl hydrogen bonding interactions between the 4-dichloroanilinium cations, the [BiCl6]3- anions and water molecules forming a 3D network. The Hirshfeld surface calculation was conducted to investigate: intermolecular interactions, associated 2D ?ngerprint plots, and enrichment ratio, indicating the relative contribution of these interactions in the crystal structure quantitatively. Thermal analysis reveals the decomposition of the compound at 180 (cid:2)C. The quantum mechanical calculations such as geometry optimization, vibrational frequencies, simulated UVeVisible spectrum, FMOs analysis were made together with the experimental studies. Furthermore, the new synthesized compound was screened for its antibacterial activity. Results revealed that it has the most effective activity against all the tested bacteria compared to the amine alone and to the BiOCl.
关键词： Hirshfeld surface analysis,Hybrid material,DFT calculations,Hexachlorobismuthate(III),X-ray diffraction,Antimicrobial activity
更新于2025-09-23 15:23:52
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Effect of electron-donating groups on the electrochemical and optical properties of indoline substituents as hole transport materials: A computational study
摘要： The e?ect of electron-donating property of the groups attached to the indoline substituents with two di?erent low-cost cores (tetraazafulvalene and pyrene) as new hole transport materials (HTMs) was studied on their electrochemical and optical behaviors. The calculations were carried out based on the theoretical approaches including density functional theory (DFT), time-dependent density functional theory (TD-DFT), and Marcus theory. Some important parameters, such as hole mobility, solubility and stability, absorption and emission spectra, Stokes shift, and HOMO/LUMO energies and distributions were obtained and discussed. It was found that the HOMO of all the designed structures is distributed more widely than their LUMO. The results showed that the maximum absorption band of the designed HTMs is red shifted as the electron-donating ability increases. It is also predicted that TAF/indoline-OMe and Py/indoline-NH2 with the hole mobility of 2.90 × 10?3 and 1.51 × 10?3 cm2 V?1 s?1, respectively give higher ?ll factor and short-circuit current density of the device.
关键词： Hole transporting materials,Perovskite solar cells,Di?erent electron-donating groups,Indoline substituents,DFT/TD-DFT,Cost e?ective
更新于2025-09-23 15:22:29