Inorganic Chemistry最新文献

Spectroscopic characterization of Hg(II)-thiolate complexes is central to the bioinorganic chemistry of Hg(II). Interpretation of ¹⁹⁹Hg NMR usually relies on data recorded for reference compounds; however, here, it is demonstrated that ¹⁹⁹Hg NMR chemical shifts may be calculated within 40 ppm of experimental values for 2-, 3-, and 4-coordinate Hg(II)-thiolate complexes, using the PBE0 functional, the QZ4P basis set on Hg and S and TZP on all other atoms, and SO-ZORA to account for relativistic effects. The chemical shift is particularly sensitive to the Hg-S bond length (ca. 300 ppm/0.1 Å per Hg-S bond), while it is less sensitive to changes of S-Hg-S angles (up to 40 ppm/10 degrees ¹). Rigid rotation of the methyl groups around the Hg-S axis in model complexes, [Hg(SCH₃)_n]^2-n (n = 2, 3, 4), may give rise to changes of up to 100 ppm. Finally, calculations of the ¹⁹⁹Hg NMR chemical shift for a model system of the Hg(II) binding site in the MerR protein demonstrate that experimental ¹⁹⁹Hg NMR chemical shift data in combination with DFT calculations may be used as a constraint in the optimization of Hg(II) sites in proteins.

The thermodynamically controlled self-assembly of bis-bidentate quaterpyridine ligand, L = 2,2':5',5″:2″,2‴-quaterpyridine, with Cr^II and subsequent oxidation to Cr^III yields the first photoluminescent tetrahedral [Cr^III₄L₆]¹²⁺ molecular cage. Single-crystal X-ray diffraction reveals the presence of two homochiral cages (ΛΛΛΛ and ΔΔΔΔ) in the unit cell that crystallize as a racemic mixture. Additionally, a PF₆ anion is observed inside the cavity, in line with isostructural cages built with Ni^II or Fe^II. Each corner of the polyhedron is occupied by weakly antiferromagnetically coupled {Cr(bipy)₃}³⁺ (bipy = 2,2'-bipyridine) patterns, as revealed by magnetometry. Upon light excitation in the UV-vis region, spin-flip luminescence from the ²E/²T₁ excited states with a maximum at 727 nm (13755 cm^-1) was detected at room temperature. The measured excited state lifetime of 183 μs is longer than the 102 μs recorded for the mononuclear [Cr(bipy)₃]³⁺ complex under anaerobic conditions, whereas the luminescence quantum yields are in the same order of magnitude and amount to 10^-2 %. The photoluminescence brightness, B, calculated using the maxima of the absorption spectra for both species, goes from 14 M^-1·cm^-1 for the mononuclear compound to 90 M^-1·cm^-1 for the tetrahedral cage. This 6-fold improvement is observed across the entire excitation wavelength range, and it is due to the incorporation of four light-harvester units in the molecular cage.

Glutarimidedioxime is a cyclic amidoxime moiety formed during the synthesis of amidoxime-functionalized fibers and apparently facilitates the extraction of uranium from seawater. Herein, we comprehensively explore differences between molybdenum and vanadium coordinated by glutarimidedioxime. The high adsorption of vanadium is explained by the formation of rare nonoxido vanadium(V) complexes, where each bare V⁵⁺ is coordinated with two tridentate glutarimidedioxime ligands. By contrast, molybdenum is coordinated by only one glutarimidedioxime ligand, and the oxido Mo═O bonds in molybdate cannot be displaced by the ligand. Under seawater conditions, vanadium is fully complexed. Meanwhile, approximately 25% of molybdenum ions are in the form of free molybdate even if the concentration of glutarimidedioxime is 100000 times that of molybdenum. Glutarimidedioxime was expected to be more stable in the presence of metal ions than without them. However, complexation with molybdenum accelerated the degradation of the glutarimidedioxime ligand to release hydroxylamine. Molybdenum(VI) was then reduced by hydroxylamine, which itself was oxidized into nitrosyl. Vanadium heavily outcompetes adsorption of uranium, while molybdenum causes the degradation of glutarimidedioxime; the latter issue has previously been neglected and was first reported here.

The investigation of bonding interactions between superatoms continues to be a largely unexplored area of study. In this study, we present the synthesis and characterization of two F₂-type superatomic molecules [Au₂Ag₂₅(C₇H₄NOS)₁₃(DPPB)₃] and [Au₉Ag₁₈(C₅H₄NS)₁₁(DPPM)₅]²⁺ (Au₂Ag₂₅ and Au₉Ag₁₈ for short, respectively). The overall structures were confirmed via X-ray crystallography, revealing the horizontal expansion of the biicosahedral Au₂Ag₂₁ yielding [Au₂Ag₂₅(C₇H₄NOS)₁₃(DPPB)₃] and vertical expansion of the biicosahedral Au₈Ag₁₅ yielding [Au₉Ag₁₈(C₅H₄NS)₁₁(DPPM)₅]²⁺. Furthermore, their electronic structures were elucidated through density functional theory (DFT) calculations. Spectroscopic analysis of electronic absorption characteristics, in conjunction with Tamm-Dancoff approximation DFT (TDA-DFT) calculations, revealed that the Au₂Ag₂₁⁽⁺⁹⁾ and Au₈Ag₁₅⁽⁺⁹⁾ cores were analogues of the F₂ molecule in electronic configuration.

In this study, we report the synthesis and full characterization of five novel ruthenium(II) cymene complexes with the general formula [Ru(cym)(L')Cl], featuring N,O- and N,N-coordinating pyrazolone-based hydrazone ligands. We have characterized these complexes using single X-ray crystallography, Fourier-transform infrared spectroscopy (FT-IR), Nuclear magnetic resonance (NMR), elemental analysis, and Electrospray Ionization Mass Spectroscopy (ESI-MS). Crystallographic analysis confirmed that all of the complexes have a similar type of half-sandwich, pseudo-octahedral "three-legged piano-stool" geometry where the cymene moiety displays the typical η⁶-coordination mode and the hydrazone ligands coordinate to the Ru(II) center in a bidentate fashion. These complexes, with multiple catalytic sites, demonstrated high efficiency in catalyzing one-pot cascade deacetalization-Knoevenagel condensation reactions under mild conditions, achieving up to 92% of final product yield at 75 °C after 4 h of reaction time under solvent-free condition. Additionally, DFT calculations provided insight into the catalytic mechanism, suggesting a pathway driven by metal-ligand cooperation, assisted by the basic oxygen site of the pyrazolone ring and by the weakly acidic character of the NNH proton of the hydrazone group.

An extended trisazo dipyridyl ligand, L, and its copper(I) complex, [1]⁺, were synthesized and fully characterized. Complex [1]⁺ has five coordination geometry satisfied by ligand L. L has a low-lying π* orbital; thus, [1]⁺ showed very facile multiple ligand-based redox events. Moreover, due to the strong π-acceptor nature of L, the Cu(II)/Cu(I) redox potential of [1]⁺ was anodic (0.62 V). The redox events of both L and [1]⁺ were characterized using various spectroscopic studies and density functional theory (DFT) calculations. Taking advantage of the multiple facile ligand-based reductions in [1]⁺, the Glaser coupling reaction of terminal alkynes was explored. Various kinds of alkynes were found to be effective when using [1]⁺ as a precatalyst. The mechanism of the reaction was investigated thoroughly by several controlled experiments, isolation, and characterization of the intermediates using various spectroscopic studies as well as by single-crystal X-ray structure determination. These studies showed that the L in [1]⁺ acted not only in the electron transfer events but also as a locus for binding the substrate, breaking and forming bonds, and, finally, releasing the product. Thus, here, the metal mainly acted as a spectator and ligand L acted as an actor.

This study explores a Hofmann-type clathrate, {Fe₂(2,4-(OCH₃)₂-pbpy)₂(H₂O)₂[μ₂-Pt(CN)₄][μ₃-Pt(CN)₄]₂·4H₂O}, which exhibits a thermally activated electron transfer (ET) without spin crossover. Synthesized as microcrystalline powders and single crystals, this compound reveals significant structural changes upon variation of the temperature, including alterations in the iron coordination sphere due to the large movement of the bipyridinium ligand. These changes correlate with a thermochromic hysteretic transition from yellow to orange. Detailed characterizations using X-ray diffraction and IR spectroscopy indicate the involvement of nonbridging CN^- moieties as electron donors and bipyridinium units as acceptors. This result deepens our understanding of ET in Hofmann-type clathrates.

Two organic-inorganic cadmium thiocyanates, namely, Cd(SCN)(l-C₅H₈NO₂) (1) and Cd(SCN)₂(l-C₅H₉NO₂) (2), have been synthesized using l-proline as the bridging ligand. The two compounds have double-chain-like and layered structures, respectively. They feature moderate second-harmonic-generation responses (0.33 × KH₂PO₄ for 1 and 1.58 × KH₂PO₄ for 2), wide band gaps (4.68 eV for 1 and 4.59 eV for 2), and large birefringences (0.210 at 546 nm for 1 and 0.295 at 546 nm for 2). The structure-property relationship was explicated by first-principle calculations based on density functional theory.