Dalton Transactions最新文献

The structures and energetics of the binuclear methylphosphinidene complexes of cyclopentadienylruthenium carbonyls of the type [MePRu₂(CO)_nCp₂] (n = 4, 3, 2, 1) have been investigated for comparison with their previously studied iron analogues. For the tetracarbonyls and tricarbonyls [MePM₂(CO)_nCp₂] (n = 4, 3) substituting ruthenium for iron has relatively little effect on the energetically preferred structures. Thus such structures have two-electron donor bridging MeP groups with no metal–metal bond for the tetracarbonyls and a metal–metal single bond for the tricarbonyls. This leads to favored 18-electron configurations for both ruthenium atoms in all cases. However, the higher ligand field strengths of ruthenium complexes relative to analogous iron complexes have major effects on the energetically preferred structures for the dicarbonyls and monocarbonyls [MePM₂(CO)_nCp₂] (M = Fe, Ru; n = 2, 1). Thus the 11 lowest energy structures for the dicarbonyl [MePFe₂(CO)₂Cp₂] are triplet or quintet spin state structures whereas the 6 lowest energy structures for the ruthenium analogue [MePRu₂(CO)₂Cp₂] are all singlet structures. These low-energy singlet [MePRu₂(CO)₂Cp₂] structures include species in which both ruthenium atoms attain the favored 18-electron configurations in different ways: either by a Ru–Ru single bond and an agostic C–H–Ru interaction from the methyl group, a Ru–Ru single bond and a four-electron donor bridging MeP ligand with PRu double bonds, or a formal RuRu double bond with a two-electron donor bridging MeP ligand. The 8 lowest energy structures for the diiron monocarbonyl [MePFe₂(CO)Cp₂] are all triplet or quintet spin structures whereas the lowest energy structure for the diruthenium monocarbonyl [MePRu₂(CO)Cp₂] by more than 20 kcal mol⁻¹ is a singlet structure with a formal RuRu double bond and bridging CO and four-electron donor MeP groups. Thermochemical information predicts such monocarbonyl derivatives to be the dominant binuclear decarbonylation products of the tricarbonyls [RPRu₂(CO)₃Cp₂] by thermal or photochemical methods.

Herein, we show two cases of pillar-layered MOFs which are built solely with one kind of three-dimensional (3D) ditopic ligand. The ligand in both structures functions not only as an intralayer linker in the layer but also as a “pillar” between adjacent layers. Such multi-functionality of the linker is accompanied by uncommon asymmetric 10-c metal hexamer or 7-c tetramer nodes, which have never been reported in previous 3D MOF structures.

Three novel organic–inorganic polyoxoniobate-based compounds modified with Cu(II) amine complexes were synthesized under hydrothermal conditions with the chemical formulas as follows: K_0.5[Cu(enMe)₂]₄[K_0.5SiNb₁₂O₄₀(VO)_4.25](OH)_1.5·9H₂O (1), K_0.5[Cu(enMe)₂]₄[K_0.5H₂PNb₁₂O₄₀(VO)₂]·12.5H₂O (2), and K_0.5[Cu(enMe)₂]₄[K_0.5H₂VNb₁₂O₄₀(VO)₂]·12.5H₂O (3) (enMe = 1,2-diaminopropane). These compounds were characterized by single crystal X-ray diffraction, infrared spectroscopy (IR), UV-Vis spectroscopy, elemental analysis and powder X-ray diffraction (PXRD) analysis. Notably, while these three compounds exhibit identical cell parameters, they possess distinct stoichiometric compositions and differing polyoxometalate building block structures. Typically, compounds with the same cell parameters are classified as isostructural, sharing identical structures with only minor elemental variations in their compositions. To the best of our knowledge, compounds 1–3 represent the first instances of compounds that share the same cell parameters yet are not isostructural. In this study, we not only synthesized these three compounds and thoroughly examined the differences in their structures and properties, but also investigated their catalytic performances as catalysts for the oxidation of styrene.

This study presents the successful synthesis of two perylenediimide (PDI)-based ortho-carborane (o-carborane) derivatives, PDI–CB1 and PDI–CB2, through the insertion of decaborane into alkyne-terminated PDIs (PDI1 and PDI2). The introduction of o-carborane groups did not alter the optical properties of the PDI units in solution compared to their carborane-free counterparts, maintaining excellent fluorescence quantum yields of around 100% in various solvents. This was achieved by using a methylene linker to minimize electronic interaction between PDI and o-carborane, and by incorporating bulky o-carborane groups at imide- position to enhance solubility and prevent π–π stacking-induced aggregation. Aggregation studies demonstrated that PDI–CB1 and PDI–CB2 have greater solubility than PDI1 and PDI2 in both nonpolar and aqueous solvents. Despite the steric hindrance imparted by the o-carborane units, the solid state emission of PDI–CB1 and PDI–CB2 was affected by aggregation-caused fluorescence quenching. However, solid PDI–CB1 preserved bright red excimer-type emission, which persisted in water-dispersible nanoparticles, indicating potential for application as a theranostic agent combining fluorescence bioimaging with anticancer boron neutron capture therapy (BNCT) due to its high boron content.

We report the synthesis, characterization, anti-cancer activity and mechanism of action of a novel water-soluble Cu(II) complex with salicylidene carbohydrazide as the ligand and o-phenanthroline as the co-ligand. The synthesized complex (1) was characterized by FT-IR, EPR, and electronic spectroscopy, as well as single crystal X-ray diffraction. This compound was found to be paramagnetic from EPR spectra and X-ray crystallography revealed that the molecule crystallized in an orthorhombic crystal system. The crystal lattice was asymmetric containing two distinct binuclear copper complexes containing the Schiff base as the major ligand, o-phenanthroline as a co-ligand, two nitrate anions, and two water molecules. The Cu(II) in the first site coordinated with the enolised ligand comprising enolate O⁻, phenolate O⁻, and the imine N and N,N from o-phen. The major part of this complex exists as Cu(II) coordinated with two H₂O molecules at the second site with nitrate acting as the counter anion. However, a smaller portion of the complex exists where Cu(II) is coordinated with NO₃⁻ and H₂O, and the remaining water molecule acts as lattice water. It was tested for DNA binding and cleavage properties which revealed that it binds in an intercalative mode to CT-DNA with K_b value of 1.25 × 10⁴ M⁻¹. Furthermore, cleavage studies reveal that the complex has potential for efficient DNA cleavage under both oxidative and hydrolytic conditions. It was able to enhance the rate of cleavage by 2.8 × 10⁸ times. The complex shows good cytotoxicity to breast cancer monolayer (2D) as well as spheroid (3D) systems. The IC₅₀ values for MDA-MB-231 and MCF-7 monolayer culture was calculated as 1.86 ± 0.17 μM and 2.22 ± 0.08 μM, respectively, and in (3D) spheroids of MDA-MB-231 cells, the IC₅₀ value was calculated to be 1.51 ± 0.29 μM. It was observed that the complex outperformed cisplatin in both breast cancer cell lines. The cells treated with complex 1 underwent severe DNA damage, increased oxidative stress and cell cycle arrest which finally led to programmed cell death or apoptosis in triple negative breast cancer cells through an intrinsic pathway.

We report an aniline ligand (1) with two bis(pyrazolyl)alkane arms, and its cationic, dizinc complexes. XRD, NMR, and modelling of the dizinc complexes resulted in an unprecedented, dynamic μ-anilide core. Compared with published μ-phenolate analogues, our μ-anilide complexes show higher activity and divergent counterion trends in ring-opening polymerization of rac-lactide.

A new biomimetic model complex of the active site of acireductone dioxygenase (ARD) was synthesized and crystallographically characterized ([Ni(II)(N-(ethyl-N′Me₂)(Py)(2-t-ButPhOH))(OTf)]-1). 1 displays carbon–carbon oxidative cleavage activity in the presence of O₂ towards the substrate 2-hydroxyacetophenone. This reactivity was monitored via UV-Visible and NMR spectroscopy. We postulate that the reactivity of 1 with O₂ leads to the formation of a putative Ni(III)-superoxo transient species resulting from the direct activation of O₂via the nickel center during the oxidative reaction. This proposed intermediate and reaction mechanism were studied in detail using DFT calculations. 1 and its substrate bound derivatives display reactivity toward mild outer sphere oxidants, suggesting ease of access to high valent Ni coordination complexes, consistent with our calculations. If confirmed, the direct activation of O₂ at a nickel center could have implications for the mechanism of action of ARD and other nickel-based dioxygenases and their respective non-traditional, enzymatic moonlighting functions, as well as contribute to a general understanding of direct oxidation of nickel(II) coordination complexes by O₂.

Multinuclear molecular catalysts mimicking natural photosynthesis have been shown to facilitate water oxidation; however, such catalysts typically operate in organic solutions, require high overpotentials and have unclear catalytic mechanisms. Herein, a bio-inspired hexanuclear iron(III) complex I, Fe₆(μ₃-O)₂(μ₂-OH)₂(bipyalk)₂(OAc)₈ (H₂bipyalk = 2,2′-([2,2′-bipyridine]-6,6′-diyl)bis(propan-2-ol); OAc = acetate) with desirable water solubility and stability was designed and used for water oxidation. Our results showed that I has high efficiency for water oxidation via the water nucleophilic attack (WNA) pathway with an overpotential of only ca. 290 mV in a phosphate buffer of pH 2. Importantly, key high-oxidation-state metal–oxo intermediates formed during water oxidation were identified by in situ spectroelectrochemistry and oxygen atom transfer reactions. Theoretical calculations further supported the above identification. Reversible proton transfer and charge redistribution during water oxidation enhanced the electron and proton transfer ability and improved the reactivity of I. Here, we have shown the multimetal synergistic and electronic effects of catalysts in water oxidation reactions, which may contribute to the understanding and design of more advanced molecular catalysts.

The homoleptic hydroxy-pyridine functionalized Co(III)–NHC complex (2) demonstrates extraordinary catalytic activity towards the CO₂ cycloaddition under mild conditions. Using this catalyst and TBAB, the highest TON (666 667) and TOF (52 713 h⁻¹) were achieved compared to previously reported cobalt catalysts.

Correction for ‘Plasma-assisted fabrication of ultra-dispersed copper oxides in and on C-rich carbon nitride as functional composites for the oxygen evolution reaction’ by Mattia Benedet et al., Dalton Trans., 2024, https://doi.org/10.1039/d4dt02186j.