European Journal of Inorganic Chemistry最新文献

This report describes synthesis of a new ligand (E)-N-(4-(benzo[d]thiazol-2-yl)phenyl)-1-(quinolin-2-yl)methanimine (L1) and its three ruthenium(II) arene complexes with [RuCl₂(p-cymene)]₂ (C1), [RuCl₂(benzene)]₂ (C2), and [RuCl₂(hmb)]₂ [hmb=hexamethylbenzene] (C3). The new ligand and complexes were characterized with the help of standard spectroscopic and analytical techniques like ¹H and ¹³C{¹H} Nuclear Magnetic Resonance (NMR), Fourier transform infrared (FTIR), High-resolution mass spectrometry (HRMS), UV-Visible, cyclic voltammetry, and elemental analysis. The structure of ruthenium complex (C1) and its binding mode with ligand were authenticated with the help of single crystal X-ray diffraction. The ruthenium arene complexes (C1--C3) were used as a catalyst for the α-olefination of Methylazaarenes. First, methylazaarenes were reacted with alcohols under optimized reaction conditions to produce α-olefinated products (up to 66 %) selectively. Among the three ruthenium complexes, C1 demonstrated the highest yield of olefinated products with 5 mol % catalyst loading. Finally, selected olefin derivatives were tested for their inhibitory potential towards the aggregation of amyloid-b-40 (Aβ40) peptide relevant to Alzheimer's disease. Overall, these complexes are promising catalysts for organic transformations, and the synthesized α-olefinated derivatives could have potential applications for the development of therapeutic agents for Alzheimer's disease.

The elastic interaction causes a two-step conversion from the low-spin (LS) to the high-spin state (HS) following a femtosecond laser pulse excitation. These steps occur on different timescales: a spin conversion (elastic step) in a short time due to pressure propagation and a late spin conversion (thermal step) resulting from heat diffusion. In this paper, we provide a brief review of models for spin crossover phenomena, emphasizing the role of the difference of degeneracy of the HS state and LS state and elastic interaction due to changes in local structures. We also review theoretical approaches to these effects. Additionally, to analyze the dynamical process of spin conversion after photo-irradiation, it is necessary to consider mechanisms of heat transfer among spins. Recently, we proposed a two-temperature model that incorporates both lattice and spin temperatures, which enables us to reproduce the two steps under an early uniformization of the lattice temperature, highlighting the importance of the timescales of these processes. Furthermore, we explore possible mechanisms to separate the two steps by examining the different timescales of processes of spin conversions by mechanical and entropic forces, and also by considering changes of local temperature due to spin conversion.

Four organometallic complexes featuring identical conjugated diimine ligands and varying transition metal centers (Rh(III), Ir(III), Ru(II), and Os(II)) were synthesized. A comprehensive investigation of the photophysical properties of these complexes and their corresponding diimine ligands was conducted by UV-vis absorption, emission, and transient absorption (TA) spectroscopy, as well as optical power limiting (OPL) measurements. The incorporation of fluorene components with alkyl chains enhanced the π-conjugation of the ligand, prevented intermolecular π-π stacking, and improved complex solubility. The diimine ligands showed a slight solvation effect in their emission spectra, indicating that the main property of their emissive state was intramolecular charge transfer (CT). According to the valence states of the four complexes, they can be divided into two classes (Rh(III), Ir(III)) and (Ru(II), Os(II)). For TA spectrum, the former group exhibited positive ΔOD values across the 400~800 nm range, while the latter showed large inverted peaks at 420~500 nm due to significant ground-state absorption in this wavelength range. Additionally, the optical limiting conduct of the complexes observed the order: 1 d>1 a>1 c>1 b. Complex 1 d exhibits powerful reverse saturable absorption (RSA) properties at 532 nm and could probably be used as an wonderful nonlinear absorbing material.

In the case of N-alkylation reaction via borrowing hydrogen (BH) methods, imine hydrogenation is one of the critical steps. Mechanistically, the majority of imine hydrogenation, either by dihydrogen gas or by alcohol in case of BH methods, follow two-electron chemistry, where a metal-hydride intermediate plays a pivotal role. Herein we demonstrate a completely complementary protocol, where the hydrogenation is governed by a radical pathway. Such a pathway is adopted from the redox active nature of the azophenolate ligand backbone. The facile and reversible 2e⁻/2H⁺, azo/hydrazo redox couple in a nickel catalyst helps in storing the hydrogen from alcohol dehydrogenation. An imine substrate is reduced by one-electron from the azo motif with the assistance of the nickel center. The reduced imine drives a critical hydrogen atom transfer step from the hydrazo motif to conduct the hydrogenation. A set of kinetics experiments including Eyring analysis, radical inhibition experiment along with computational probation attest for the radical-promoted hydrogenation mechanism.

Three variants of 5,6-dihydro-1,4-dithiin-2,3-(1’,3’-dithiole-2’-thione) (dddt) bearing up to four substituents on the ethylene bridge have been obtained by hetero-Diels-Alder reaction. The substituted dddt derivatives have the advantage of providing modulation of the steric hindrance and stereogenic centres, and represent valuable intermediates for both tetrathiafulvalene (TTF) and metal-dithiolene complexes. Within this work, disubstituted and tetrasubstituted dddt derivatives have been used for the synthesis of Ni(II) monoanionic and neutral complexes, as well as for tetra- and octa-methylated EDT-TTF and BEDT-TTF (EDT=ethylenedithio, BEDT=bis(ethylenedithio)) derivatives. While the influence of the bulkiness and number of the substituents is observed in the solid state packing of both types of materials (complexes and TTF), the absence of the counterion in the case of the neutral complexes translated into increased intermolecular interactions between the donors and the formation of 1D and 2D layers. The two examples of tetrasubstituted TTF radical cation salts reported in here show semiconducting behaviour due to the formation of dimers and lateral interactions through the S atoms. Our findings highlight the importance of substitution on these type of dddt precursors and their potential for electroactive molecular materials.

Dion-Jacobson-type layered perovskite compounds A′SmNb₂O₇ (A′=Rb, K, Na, Li, H) were synthesized using solid-state and ion-exchange methods. While the parent solid-state product RbSmNb₂O₇, has previously been studied, the ion-exchanged compounds were obtained and studied for the first time. The phase and chemical purity of the compounds were confirmed by X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDX). The crystal structures of RbSmNb₂O₇ (I2 cm, a=0.54356(1) nm, b=0.53935(1) nm, c=2.1891(5) nm), KSmNb₂O₇ (I2 cm, a=0.53660(7) nm, b=0.54481(6) nm, c=2.1527(1) nm) and LiSmNb₂O₇ (B2 cm, a=0.54546(4) nm, b=0.53567(4) nm, c=2.04582(5) nm) were refined using the Rietveld method. Polyhedral distortions in these structures have been studied in detail. The thermal behavior of the compounds has been determined using differential thermal analysis (DTA), revealing that A′=Na, Li and H compounds are metastable hydrates, while A′=Rb and K compounds are stable. The optical band gap, valence band edge, and conduction band edge potentials of the compounds obtained were calculated using diffuse reflection spectroscopy data. A photocatalytic experiment was performed on the degradation of methylene blue under ultraviolet light. All of the samples obtained showed some asctivity in the reaction of dye photooxidation.

Despite extensive research into developing efficient and environmentally friendly catalysts for converting CO₂ over the last decade, the search for a robust and cost-effective catalytic system is ongoing. This study describes developing and applying a new catalytic system using inexpensive ferrate and zincate anions immobilized on easily available commercial ion exchange resins (IER) to produce cyclic carbonates from CO₂ with high efficiency and low cost. Two polystyrene-based anion exchange resins, Amberlyst^TM A26-Cl (A26-Cl) and Amberlite^TM IRA-400-Cl (IRA400-Cl), were compared. The results demonstrated the catalysts’ remarkable activity under mild conditions and demonstrated the synergistic effect between the polystyrene support and the active ammonium metallates, presenting a scalable, eco-friendly method for cyclic carbonate production using waste CO₂. A Design of Experiment (DoE) approach was implemented to optimize the catalytic cycloaddition of CO₂. The reaction scale-up to produce a 5 g batch of propylene oxide and conducting recycling tests demonstrated that the catalyst retained its activity over four cycles. The research also explored the use of various epoxides and found that terminal epoxides produced very good yields. In summary, this study introduces a cost-effective, scalable method for converting CO₂ into valuable cyclic carbonates, leveraging the synergistic effects of polystyrene supports and active ammonium metallates.

Materials based on small molecules characterized by multi-component short and long-lived emissive behaviour are extremely desirable for various applications. The derivative of cyclic triimidazole (TT) functionalized with a carboxylic group, namely TT-COOH, is isolated, investigated and used as coordinative ligand to obtain a series of isomorphous mononuclear complexes of general formula [M(TT-COO)₂(H₂O)₂] (M=Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II)). Crystals of TT-COOH display aggregation induced enhanced emission (AIEE) comprising dual fluorescence and dual phosphorescence of molecular origin together with an aggregation induced long lived, low energy phosphorescence. Emissive features are retained in crystals of the Zn(II) and Cd(II) complexes, where the metal plays the role of an external heavy atom perturber, but strongly quenched in the others. The mechanisms involved in the photophysics of TT-COOH and its metal complexes have been disclosed thanks to combined structural, spectroscopic and computational investigations which reveal the presence of anti-Kasha emissions.

The μ-phenoxido-bridged dinuclear copper(II) complex, [Cu₂(L¹)₂(dmso)(MeOH)] (1), has been synthesized using N′-(4-(diethylamino)-2-hydroxybenzylidene)-1-naphthohydrazide (H₂L¹) as ligand. The structural analysis of 1 reveals that the coordination geometry at the copper ions is best described as a square pyramidal with a Cu⋅⋅⋅Cu distance in the dinuclear complex of 303 pm which is supported by hydrogen bonding between the two apical oxygen donor ligands (O⋅⋅⋅O 277 pm). Magnetic studies indicate that 1 exhibits a strong antiferromagnetic interaction between the two copper(II) ions with a coupling constant of J=−450 cm⁻¹ ($$). The magnetic exchange is transmitted through the central [Cu₂(OR)₂]²⁺ core, a fragment for which different magneto-structural correlations have been reported depending on the substituent at the bridging oxygen atom. However, the properties of complex 1 cannot be explained by any of the established correlations. Nevertheless, complex 1, together with the series of compounds based on an acylhydrazone ligand framework reported so far, shows a magneto-structural correlation as a function of the Cu−O−Cu bridging angle that significantly differs from all previously reported.

Andrographolide (ADG) encapsulation was carried out on MOFs MIL-53(Al) and ZIF-8 by high-pressure (0.3 GPa) contact. This methodology is not only environment-friendly but also energy/time-saving and gives rise to ADG-MOFs with physical features equivalent to those of materials obtained by common liquid phase encapsulation. The loaded MOFs were characterized through TEM, SEM, XRD, TGA, FT-IR, BET, and NMR. The observed decrease in the intensity of ADG XRD peaks is due to the adsorption of ADG into the MOFs. TGA showed the decomposition step of ADG in the range of 200–300 °C in both loaded MOFs. FT-IR also showed intense signals of the ADG in the synthesized materials. The dissolution profile of ADG in MIL-53(Al) in PBS (pH=7.4) was carried out showing that the drug was released up to 96 % after 75 h. Solid-state NMR confirmed the interactions between ADG molecules and ZIF-8 groups and the formation of a hydrogen bond between the carboxylic group of ADG and the hydroxyl group of MIL-53(Al). Coefficient partition studies determined that both MOFs did not improve the hydrophilicity of the ADG, due to the loading of the drug preferably occurring by interactions in the hydrophobic areas within the pores of the MOFs.