Inorganic Chemistry最新文献

Halogenation of ligands intensely modulates the redox and photophysical properties of transition-metal complexes, yet fully halogenated systems remain largely unexplored. Here we report the synthesis and structural characterization of homoleptic Ni(0) complexes with perhalogenated aryl isocyanide ligands [Ni(CN-C₆X₅)₄] (X = F, Cl). Comparative electrochemical studies reveal a dramatic anodic shift of the Ni(0)/Ni(I) couple from -0.60 V in [Ni(CN-C₆H₅)₄] to +0.03 V vs Fc^+/0 for the perfluorinated species, reflecting the exceptional π-acceptor strength resulting from the C-H/C-F persubstitution. Surprisingly, metal-to-ligand charge-transfer (MLCT) absorption energies remain largely unchanged, a result supported by DFT calculations showing concurrent stabilization of both the Ni-centered HOMO and ligand-based LUMO. In contrast, the perchlorinated complex exhibits a red-shifted MLCT band due to asymmetric frontier-orbital tuning. Ultrafast transient absorption spectroscopy demonstrates ³MLCT excited states with lifetimes in the regime of 66-141 ps for all complexes. These findings establish perhalogenated isocyanides as powerful ligands for controlling excited-state redox potentials without altering excitation energies, an attractive feature for the rational design of robust Ni-based photoredox catalysts. More broadly, our findings establish ligand perhalogenation as a design strategy for developing new photoactive first-row transition metal complexes with potential applications in luminescent devices, photocatalysis, and photodynamic therapy.

The mechanism of Ir(III)-catalyzed allylic C-H alkynylation of unactivated olefins with bromoalkynes has been investigated using density functional theory (DFT). The previously proposed Ir(III)-Ir(V)-Ir(III) redox cycle was found to be energetically inaccessible under the reported mild conditions. In contrast, our study reveals a distinct Ir(III)-only catalytic pathway, in which all elementary steps are mediated within the Ir(III) oxidation state. In this mechanism, C-C coupling of the two substrates is achieved through insertion of the bromoalkyne into the Ir-C bond of an η³-allyl-Ir(III) intermediate, a step identified as turnover-limiting and responsible for the observed regioselectivity favoring the linear product. Silver salts, beyond acting as halide scavengers, play multiple essential roles by promoting C-H activation and enabling debromination, thereby ensuring efficient product release and catalyst regeneration. These findings revise the mechanistic picture of this transformation and establish Ir(III) catalysis as the key driving force, while highlighting a distinct functional role of silver salts in redox-neutral C-C coupling reactions.

The preparation of α-alkylidene cyclic carbonates through a cyclization reaction of propargylic alcohols with CO₂ is important in the industrial process. Herein, a novel mixed-valence heterometallic Cu/Eu-based cationic framework, 1-Eu, was successfully synthesized. The material features a unique 14 Å nanocage structure and was effectively employed in the catalytic conversion of propargylic alcohols with CO₂. 1-Eu exhibits remarkable stability in various solvents as well as under acidic and basic conditions, and can maintain the framework stability even in the presence of the strong organic base DBU. Catalytic evaluations demonstrate that 1-Eu can efficiently promote the conversion of propargyl alcohol and CO₂ to α-alkylidene cyclic carbonates under mild conditions. Furthermore, it demonstrates high catalytic activity in the conversion of the biomacromolecule norethindrone with CO₂. Notably, even when low-concentration CO₂ in simulated flue gas is used as the carbon source, 1-Eu remains highly effective in catalyzing the conversion of propargyl alcohol substrates to the corresponding α-alkylidene cyclic carbonate products. The results of the control experiment show that the synergistic catalytic effect between Cu^I/Cu^II and Eu^III plays a crucial role in the activation of CO₂ and propargyl alcohol, thereby facilitating the catalytic reaction.

Niobium polyoxometalates (Nb-POMs) form in alkaline media, which limits their use as ligands for acidic cations, particularly lanthanides and actinides. Metal-Nb-POM moieties have the potential for emergent and enhanced properties, based on strong complexation behavior and high stability of the resultant materials. Here, we probe interactions of lanthanides (Pr³⁺, Nd³⁺, Sm³⁺, Eu³⁺, Tb³⁺, Dy³⁺) and actinides (Am³⁺, Cm³⁺) with a Nb-POM [Nb₆O₁₉]^8- (Nb₆) in alkaline media. Nb₆, the most charge-dense Nb-POM, enhances f-element luminescence emission by up to × 10⁶, via Nb-POM-mediated sensitization. Lengthened emission lifetimes correlate with the release of the metal-cation hydration sphere, replaced by multidentate Nb-POMs. The Nb₆-Ln(An) complexes resist carbonate and phosphate displacement, and Nb₆-Ln(An) complexation is retained upon isolation of the solids from solution. Electrospray ionization mass spectrometry (ESI-MS) and Raman spectroscopy both indicate the formation of the unprecedented Peacock-Weakley Nb-POM ([Ln^III(Nb₅O₁₈)₂]^19-) in addition to simple Nb₆-Ln coordination complexes. Luminescence emission spectra support the presence of simple Nb₆-Ln coordination complexes. Small-angle X-ray scattering (SAXS) evidence the formation of Ln-Nb-POM aggregates. This foundational investigation highlights the potential of Nb-POMs as metal-ligands at basic pH, with value-added properties including scaffolding extended materials and controlling light absorption and emission.

Precise structural design is vital for advancing high-performance birefringent crystals used in mid-infrared polarizing devices. Mixed anion systems, particularly chalcohalides, present a promising avenue by synergistically combining the broad infrared transparency of chalcogenides with the band gap-widening capability conferred by halide ions. Guided by this approach, a novel chalcohalide birefringent crystal, Ba₄CdGa₂S₆F₄, was successfully designed and synthesized by the cation and anion cosubstitution strategy. This compound was derived from the parent phase Ba₅Ga₂S₈ by partially replacing one Ba²⁺ cation with one Cd²⁺ cation and two S^2- anions with four F^- anions. Optical characterization via the UV-vis-NIR diffuse reflectance measurement reveals that Ba₄CdGa₂S₆F₄ exhibits a large optical band gap of 3.78 eV. And the broad infrared transparency of Ba₄CdGa₂S₆F₄ is confirmed for the material via both Raman and Fourier transform IR spectroscopy. First-principles calculations indicate that Ba₄CdGa₂S₆F₄ has moderate birefringence with a value of 0.057 at 1064 nm, representing a 26.6% increase over the parent compound Ba₅Ga₂S₈. This work not only reports a promising infrared birefringent crystal with large band gap but also demonstrates that the cation and anion cosubstitution is an effective strategy for designing novel functional crystalline materials.

Multifunctional materials with multiple physical channel responses are extensively used in various high-tech fields due to their superordinary electrical, magnetic, optical, thermal, acoustic, and other functions. Despite significant progress in functional materials, the ones with multiphysical channel switching responses have long been a great challenge. Herein, we present a thermochromic organic-inorganic hybrid ferroelastic semiconductor [PPY]₂[CuCl₄] (PPY = 4-pyrrolidinopyridine) with three physical channel switching responses in thermal/electrical/optical properties. [PPY]₂[CuCl₄] undergoes a ferroelastic phase transition at 317 K, characterized by the Aizu notation mmmF2/m, accompanied by the emergence and disappearance of ferroelastic domains during the phase transition. It also exhibits continuous and stable switching between high- and low-dielectric states in the vicinity of 417 K. Moreover, it exhibits intriguing thermochromism (green ↔ chartreuse) and possesses potential semiconductor characteristics with a band gap of 2.31 eV. This study contributes to the advancement of ferroelastic materials and devices capable of multiphysical channel responses.