Organometallics最新文献

This study extends our preliminary investigation of ferrocene-containing desmuramylpeptides as potential agonists of nucleotide binding oligomerization domain containing protein 2 (NOD2). We report the rational design, chemical synthesis, conformational characterization and biological evaluation of 13 novel ferrocene conjugates with the desmuramyldipeptide l-Ala–D-isoGln (10c/g, 11a–c, 13d/f) and tripeptide Gly–l-Val–d-Glu–(OEt)₂ (12a–f). Detailed spectroscopic analysis revealed the presence of conformationally flexible structures driven by weak intramolecular hydrogen bonds. The ferrocene-carrying desmuramylpeptides were evaluated for their in vitro NOD2 agonist activity on the HEK-Blue NOD2 reporter cell. Of the ferrocene derivatives tested, conjugates 12b and 12c exhibited the strongest NOD2 agonist activity of the series, with the lowest EC₅₀ values of 44.1 and 252.6 nM, respectively. The best performing compound 12b also induced cytokine production in peripheral blood mononuclear cells (PBMCs), both alone and in combination with lipopolysaccharide (LPS). This work thus presents the first potent ferrocene-modified NOD2 agonists and provides a framework for the rational design and further optimization of ferrocene-based NOD2 immunomodulators.

Antiaromatic pentalenes and heteropentalenes are interesting for organic optoelectronics and semiconductors due to their low HOMO–LUMO gaps. However, disilapentalenes (silolosiloles, here called SSs), carrying two Si=C double bonds, are a rarely explored class of compounds. Herein, we probed the formation of antiaromatic SS compounds 1b–3b, by density functional theory calculations, from their corresponding precursors diketosilolosiloles (DSSs) 1a–3a, through [1,3]-Si → O sigmatropic shifts. The relative Gibbs free energy (ΔG) displays that, among several migrants (H, Me, CF₃, CN, NH₂, F, Cl, SiH₃, SiMe₃, and SiF₃), the migration of the SiF₃ group is exergonic (−7.6 kcal mol^–1), which could be further improved (−13.7 kcal mol^–1) by introducing CN groups at the β-positions to the ring’s silicon atoms, overcoming an activation barrier of ∼35 kcal mol^–1. The frontier orbital energies and natural population analysis charges on the Si and O atoms of the Si–C(−O) bond in the SS compounds display a good relationship with the ΔG. Further, it is revealed that the SS compounds have smaller HOMO–LUMO gaps and are significantly less antiaromatic than the parent pentalene. The thermally or photoinduced DSS to SS conversion could be attractive for single-molecule conductance “double” switches and logic gates.

A series of palladium complexes supported by tert-butylamine-functionalized amido-NHC ligands were synthesized and systematically evaluated with respect to their structure, electronic properties, and catalytic performance. Single-crystal X-ray diffraction confirmed distorted square-planar geometries, with greater distortion observed in Nitron-based and polydentate systems, as quantified by τ₄ and τ₄′ indices. Computational studies revealed that deprotonated Nitron-based ligands exhibit strong σ-donation and HOMOs delocalized over the ligand, enhancing electron density at the Pd center. These features translated into superior reactivity in Sonogashira, Suzuki–Miyaura, and Mizoroki–Heck coupling reactions, particularly for unreactive aryl chlorides. DFT calculations further confirmed that oxidative addition barriers are lowest for deprotonated Nitron-based ligands, supporting their role in promoting challenging bond activations. These results highlight the utility of anionic NHC ligands as a robust platform for designing next-generation Pd catalysts for demanding cross-coupling transformations.

Resistance of Plasmodium falciparum to current antimalarials necessitates new therapies. This preliminary study presents the design, synthesis, and characterization of novel 7-chloroquinoline-1,2,3-triazole hybrids incorporating aminopropyl linkers. Several compounds show submicromolar in vitro activity against both chloroquine-sensitive and -resistant strains. β-Hematin inhibition assays revealed strong activity, especially for a cationic iridium(III) complex (7), despite its limited cellular efficacy. The presence of an aminoalkyl linker, secondary amines, and metal coordination were found to be critical to enhanced antiplasmodial activity, supporting further development of these hybrids as promising antimalarial agents.

The C-tert-butyl substituted azacyclopropenylaluminate, [(SiN^Dipp)Al-η²-{NCt-Bu}K]_∞ (SiN^Dipp = (CH₂SiMe₂NDipp)₂) reacts with both aryl- and alkyl-substituted nitriles. In contrast to previously reported attempts to effect C–C bond formation between two dissimilar nitriles, these reactions enable the completely discriminating heterocoupling of t-BuCN to provide diazabutadienylaluminate dianions that bear two differentiated N═C substituents.

Hydrogenation and dehydrogenation catalysis mediated by molecular Mn catalysts were discovered in 2016. Despite their late discovery (in comparison, for instance, to related Fe and Co catalysts), many novel catalysts and catalytic reactions have since been reported with a strong focus on dehydrogenation catalysis. Here, we try to find reasons why Mn-based (de)hydrogenation catalysis made such an impact despite its late discovery. We compare the temperature dependence of the rates of well-defined Mn, Fe, and Co catalysts in ketone hydrogenation and alcohol dehydrogenation via the liberation of H₂. The Mn catalyst showed an about 40–50 °C higher thermal stability in comparison to Fe and Co catalysts. In addition, details of the decomposition of Mn and Fe catalysts at the thermal limit are reported. While the PN₅P-based Mn catalyst decomposes reversibly, the PN₅P-based Fe catalyst does it irreversibly. Interestingly, all three catalysts (Mn, Fe, and Co) are active in alcohol dehydrogenation under very mild conditions, such as 60 °C, with Mn showing the highest activity at 100 °C

This work reports the divergent metalation of trimethylsilyldiazomethane (Me₃SiCHN₂) with magnesium methyl compounds, yielding magnesium nitrilimine, diazoalkyl, and hydrazone complexes. Treatment Me₃SiCHN₂ with a β-diketiminato ligand-supported magnesium methyl compound L¹MgCH₃·THF (L¹ = [(DIPPNCMe)₂CH]⁻, DIPP = 2,6-ⁱPr₂C₆H₃) generates a magnesium nitrilimine complex [L¹Mg(μ-N–NCSiMe₃)]₂ (2) accompanied by methane elimination. Substitution of the supporting ligand with the more sterically encumbering variant [(DIPPNC^tBu)₂CH]⁻ (L²), results in the formation of a magnesium diazoalkyl complex [L²Mg(μ-κ²-C(SiMe₃)NN)]₂ (4). Crystallographic analyses confirm dimeric assemblies for both 2 and 4, yet reveal divergent ligation modes at the CNN unit. Addition of a Lewis-basic donor, 4-dimethylaminopyridine (DMAP), to the system shifts the product selectivity, yielding a magnesium hydrazone species L¹Mg(DMAP)(η²-N(Me)NCHSiMe₃) (5) via insertion of the terminal nitrogen atom of diazoalkane into the Mg–C bond.

The development of main group element species for use in chemical spaces is dependent on the continued diversification of stable and tunable substituents to leverage reactivity at these non-transition metal centers. In this work, we introduce boron-bound icosahedral carboranes as stable and tunable substituents on group 14 elements in place of more traditional alkyl and aryl groups. Herein, we report the salt melt synthesis of B(9)-carboranyl stannane as well as the first reported B(9)-carboranyl germane species from B-mercuro-carborane starting material as well as derivatization of the aforementioned species via Grignard reagents. In addition, we report the germanium disubstituted and trisubstituted carborane species, illustrating the generality of the salt melt synthetic method from B-mercuro-carborane.

Zwitterionic mixed-valence (MV) complexes offer a compelling strategy for designing charge-neutral molecular components for quantum-dot cellular automata (QCA). In this work, organometallic zwitterions 1a and 1b featuring two [Cp*(dppe)Fe] redox centers linked by a meta-phenylene ethynylene bridge and an internal carboxylate were generated and characterized. A comprehensive investigation combining cyclic voltammetry, IR, and vis–NIR spectroscopies unambiguously establishes that both 1a and 1b behave as charge-localized Robin–Day class-II MV systems. This crucial finding demonstrates that the covalently tethered counterion does not significantly alter the weak electronic communication inherent to the meta-substituted bridge. To rationalize these experimental results, density functional theory (DFT) calculations were performed. It is shown that while simplified gas-phase models inadequately predict a delocalized state, calculations incorporating a polarizable continuum model (PCM–CH₂Cl₂) successfully reproduce the experimentally observed charge localization. The agreement between the experimental data and the solvated theoretical model provides robust validation for the class-II description and confirms this zwitterionic design as a viable approach for creating charge-neutral molecular wires.