European Journal of Inorganic Chemistry最新文献

Systematic studies of metal complexes of tau protein fragments may contribute to gaining more information about its role in the neurodegenerative tauopathies. Previous studies have confirmed that the tau fragment containing the amino acid His32 has a higher metal binding affinity than other fragments containing histidine, due to the presence of a threonine near the histidine. In order to investigate the role of threonine in more detail, the Cu(II), Zn(II), and Ni(II) complexes of the tau(371–376) fragment (Ac-IETHKL-NH₂) and three tau(29–34) mutants (Ac-ATAHQD-NH₂, Ac-ATMHQD-NH₂, Ac-AAMHQD-NH₂) were examined. The presences of -TXH- moiety resulted in a small increase in the stability of the imidazole coordinated complexes as well as an observable change in the CD and UV–Vis spectra for copper(II) and nickel(II) complexes. On the other hand, the binding of nickel(II) ion to the –TXH– part of the molecule may induce hydrolytic processes in peptides. The hydrolytic process was studied in the presence of nickel(II) under different condition in peptides containing –TXH– and –XTH– moiety. The Ni(II)-induced hydrolytic process was obvious in the case of peptide containing –TXH– sequence in alkaline medium. However, the tau(371–376) fragment containing –XTH– sequence did not show any hydrolytic activity in the presence of Ni(II).

Three clamshell binuclear Pd(II) complexes have been synthesized using the primary cyclometallating ligands of phenylpyridine (ppy) and its derivatives with the ancillary clamping ligand of 3,5-di-tert-butyl-1H-pyrazole (dbp). All three complexes are fully characterized by nuclear magnetic resonance, high-resolution mass spectrometry, cyclic voltammetry, and single-crystal X-ray diffraction, and the crystal structures exhibited the Pd–Pd distances between 2.813 to 2.882 Å. It is a pioneering report of a group of binuclear Pd(II) complexes showing intensive triplet emission between 635 to 764 nm with the nature of metal-metal-to-ligand charge transfer at room temperature.

Benzimidazole is a well-known pharmacophore present in 47 FDA-approved drugs and ≈100 experimental compounds. It shows promise for other applications, including antibacterial, antifungal, antiviral, and anticancer therapies. Many derivatives modulate oxidative stress by influencing reactive oxygen species (ROS), selectively inducing cancer cell death. Additionally, structural modificationsenhance antitumor activity and facilitate conjugation with metal centers. In this study, it is focused on the hybrid ligand 2-(1H-benzo[d]imidazol-2-yl)quinolin-8-ol (L) and its Cu(II) and Ni(II) complexes (1 and 2) as potential anticancer agents. These coordination systems are characterized, and their binding stability is assessed via UVvisible titrations and density functional theory (DFT) analysis, revealing that complex 2 is more stable than complex 1. It is then investigated how the ligand and the complexes can interact with ROS, with a view to a ROS-targeting cytotoxicity. These studies, supported by DFT, indicated that L and complex 1 are generally more interactive than complex 2. When tested on various cancer cell lines, it is found that L and complex 1 demonstrated modest to good efficacy. These results suggest that L is the primary active species, complex 1 acts as a prodrug, whereas the strong interaction with Ni(II) in 2 hinders the ligand's potential.

The synthesis of a series of iridium(III) complexes supported by tris(pyrazolyl)borate (Tp^Me2) and 2-mercapto-5-(CF₃)pyridine is reported. The new complexes are obtained via the treatment of the Tp^Me2Ir(C₂H₄)₂ and Tp^Me2Ir[(η⁴-CH₂C(Me)C(Me)CH₂] precursors with equimolar amounts of 2-mercapto-5-(CF₃)pyridine at room temperature. The new heteroleptic complexes display a variety of structural features including four- or five-membered iridacycles (obtained through intramolecular CS and CN bond formation) and different iridium:mercaptopyridine ratios. All new compounds are characterized by means of ¹H and ¹³C NMR spectroscopy, elemental analyses, and by X-ray diffraction analysis. The full series of iridium(III) complexes are tested as catalysts in the transfer hydrogenation of aldehydes and ketones demonstrating good performance under low catalyst loadings (0.05 mol%) and providing good conversions. Mercury poisoning tests suggest that as the temperature of the catalytic procedure increases, the presence of a heterogeneous iridium plays an important role in the reduction process.

The Front Cover shows two cranes "building" hybrid complexes by placing organic fragments onto lacunary Keggin clusters, with heteroatoms (B³⁺, Si⁴⁺, Ge⁴⁺, P⁵⁺) highlighted by color-coded labels. A graph displays the displacement (D) and CShM distortion, with the metrics linking the interconversion between SAPR to BTPR, and vice versa. This represents how the heteroatom can control the geometry, where the X's ionic radius sets lacuna size, determining the D value and the geometry. The plot of CShM vs D shows linearity for all types of complex (mononuclear inorganic (green), mononuclear hybrid (red) and dinuclear hybrid (blue)). A D≈1.10 Å threshold separates BTPR (low D) and SAPR (high D); Ge⁴⁺/Si⁴⁺ tend to the BTPR geometry, and P⁵⁺/B³⁺ prefer to adopt a SAPR geometry. More information can be found in the Research Article by W. Cañón-Mancisidor, O. Cador and co-workers (DOI: 10.1002/ejic.202500074).

A small family of N,N,C-donor pincer-palladacycles complexes supported by (benzo-oxazole, imidazole, and thiazole)-pyridin-thiophene type ligands is obtained via CH bond activation at room temperature under atmospheric conditions. All compounds are isolated in good yield as orange to yellow-orange solids. Molecular structures are proposed based on nuclear magnetic resonance (NMR) experiments, showing significant chemical shift values on pyridin and thiophene fragments after cyclopalladation reaction, compared with the free ligand's signals. For a selected case of (benzo-oxazole)-pyridin-thiophene pincer-palladacycle, the structure is corroborated via X-ray diffraction analysis. Electrospray ionization-high resolution mass spectrometry analysis (ESI-MS) performed in fresh methanol or acetonitrile solution supports the identity of pincer-palladacycles by detecting ionic palladium-bimetallic species and dinitrogen-adducts. When MS/MS experiments are carried out for palladium-bimetallic species, spectral data point to the formation of dinitrogen-palladium. Although palladium-bimetallic species and dinitrogen-adduct ions are formed in the ESI source and in the collision-induced dissociation cell, to the best of our knowledge, this is the first report for the detection of organometallic dinitrogen-palladium species. N,N,C-donor pincer-palladacycles are found as feasible catalytic precursors on Suzuki–Miyaura reaction, showing excellent conversion, yields, and functional group tolerance.

Alkali 2,2,6,6-tetramethylpiperidides (TMP) are quintessential bases in organic chemistry. The syntheses and characterization of solvated lithium, potassium, and calcium tetramethylpiperidides are reported herein. The molecular solid-state structures of the homometallic salts [(TMP)Li(thp)]₂, [(TMP)Li(pmdta)], [(μ-TMP)K(pmdta)]₂, [(TMP)₂Ca(thp)₂], and [(TMP)₂Ca(thf)₂] are described (pmdta = N,N,N′,N″,N″-pentamethyldiethylenetriamine; thp = tetrahydropyran). In addition, the structure of the heterobimetallic [K{pmdta}{μ³-NMe₂}{μ²-TMP}Li]₂, a compound obtained upon decomposition of pmdta in the presence of (TMP)Li and ^tBuOK in petroleum ether, is also presented. These six complexes complement the body of s-block metal tetramethylpiperidides that have been structurally authenticated, with, in particular, the addition of two new calcium–TMP complexes. To probe their reactivity, these bases have been used to mediate the deprotometallation of 1,3-dimethoxybenzene in thf, followed by quenching with iodine. While the calcium complexes show little efficacy, good to high yields are achieved with the different [(TMP)M]_n (M = Li, K, Na) and (TMP)Li·^tBuOK alkali bases. The influence of temperature in this reaction is demonstrated, allowing for a better understanding of the overall behavior of the metal bases.

Inspired by the newly discovered in-plane [55555] metallo-annulene frameworks in 3D [Os]C₁₅H₁₀ ([Os] = OsL¹L² and L represents PPh₃, CO, or PEt₃ σ-ligands) and based on extensive first-principles theory calculations, herein a series of perfect 2D in-plane [55555] metallo-annulene complexes D_5h MC₁₅H₁₀ (1) (M = Pt, Pd, Ni), D_5h MC₁₅H₁₀⁻ (2) (M = Ir, Rh), D_5h MC₁₅H₁₀²⁻ (3) (M = Os, Ru), and D_5h MC₁₅H₁₀⁺ (4) (M = Au, Ag) is predicted in which the penta-coordinate transition metal center η⁵-M and [15]annulene ligand C₁₅H₁₀ match both electronically and geometrically, without the two extra σ-ligands needed on the top and bottom. Detailed bonding pattern analyses indicate that metal d_xz and d_yz orbitals in these [55555] metallo-annulenes participate in π-conjugation with the five-membered rings to form nine delocalized π-bonds in total over the molecular plane following Hückel's [4 n + 2] rule (n = 4), rendering overall π-aromaticity and extra stability to the systems. Such a structural and bonding pattern can be adapted to form the highly stable perfect on-surface [55555] metallo-fullerenes D_5d M₂C₅₀ (5) (M = Pt, Pd) and nonmetal bis([55555] metallo-annulene) sandwich complexes D_5h C₂(MC₁₅H₁₀)₂ (6) (M = Ir, Rh) and D_5h N₂(MC₁₅H₁₀)₂ (7) (M = Os, Ru).

The homologous fluoride and hydroxide complexes of gold(III) [PPh₄][(CF₃)₃AuX] [X = F (1), OH (2)] have been structurally characterized by single-crystal X-ray diffraction methods. Both of them crystallize in the P2₁/n space group, yet they are not isomorphous. Despite the intrinsic difficulty to distinguish between F⁻ and OH⁻ by X-ray diffraction, the ability of the OH ligand in complex 2 to establish intramolecular OH…F hydrogen bonding with one of the CF₃ groups in cis position enables a clear differentiation from the fluoride complex 1. Given the tendency of late-transition metal fluorides to undergo hydrolysis, much caution should be taken when ascribing the identity of a fluoride ligand by X-ray diffraction methods, especially where unusual geometries are implied.

In the course of research aimed at reproducing the functions of naturally occurring porphyrins, ongoing efforts have been directed toward introducing chirality—characteristic of many natural products—in order to mimic biological functions. Traditionally, chiral centers have been incorporated into the porphyrin framework through multistep, synthetically demanding procedures involving covalent bond formation. A more straightforward approach is proposed that utilizes a stable metal coordination bond, which was previously developed, to introduce a chiral source in a single step via axial ligation. Specifically, a novel compound is synthesized by coordinating 1,1′-bi-2-naphtholato (BINOL)—an easily accessible molecule with broad applications in asymmetric catalysis and chiroptical chemistry—to gallium porphyrin. As expected, the resulting complex exhibited high stability, with the molecular ion peak confirmed by atmospheric-pressure chemical ionization mass spectrometry. Furthermore, the structure of the compound is thoroughly characterized by single-crystal X-ray diffraction and various nuclear magnetic resonance techniques. Its chiroptical properties are also investigated using electronic circular dichroism and vibrational circular dichroism spectroscopy. This study is expected to serve as a foundation for future developments in chiroptical chemistry and asymmetric catalysis involving chiral porphyrins.