Inorganics, Volume 9, Issue 4 (April 2021) – 8 articles

Synthesis, isolation, and structural characterization of unique metal rich diamagnetic cobaltaborane clusters are reported. They were obtained from reactions of monoborane as well as modified borohydride reagents with cobalt sources. For example, the reaction of [Cp*CoCl]₂ with [LiBH₄·THF] and subsequent photolysis with excess [BH₃·THF] (THF = tetrahydrofuran) at room temperature afforded the 11-vertex tricobaltaborane nido-[(Cp*Co)₃B₈H₁₀] (1, Cp* = η⁵-C₅Me₅). The reaction of Li[BH₂S₃] with the dicobaltaoctaborane(12) [(Cp*Co)₂B₆H₁₀] yielded the 10-vertex nido-2,4-[(Cp*Co)₂B₈H₁₂] cluster (2), extending the library of dicobaltadecaborane(14) analogues. Although cluster 1 adopts a classical 11-vertex-nido-geometry with one cobalt center and four boron atoms forming the open pentagonal face, it disobeys the Polyhedral Skeletal Electron Pair Theory (PSEPT). Compound 2 adopts a perfectly symmetrical 10-vertex-nido framework with a plane of symmetry bisecting the basal boron plane resulting in two {CoB₃} units bridged at the base by two boron atoms and possesses the expected electron count. Both compounds were characterized in solution by multinuclear NMR and IR spectroscopies and by mass spectrometry. Single-crystal X-ray diffraction analyses confirmed the structures of the compounds. Additionally, density functional theory (DFT) calculations were performed in order to study and interpret the nature of bonding and electronic structures of these complexes. Full article

Metal–organic frameworks (MOFs) are emerging porous materials with highly tunable structures developed in the 1990s, while organometallic chemistry is of fundamental importance for catalytic transformation in the academic and industrial world for many decades. Through the years, organometallic chemistry has been incorporated into functional MOF construction for diverse applications. Here, we will focus on how organometallic chemistry is applied in MOF design and modifications from linker-centric and metal-cluster-centric perspectives, respectively. Through structural design, MOFs can function as a tailorable platform for traditional organometallic transformations, including reaction of alkenes, cross-coupling reactions, and C–H activations. Besides, an overview will be made on other application categories of organometallic MOFs, such as gas adsorption, magnetism, quantum computing, and therapeutics. Full article

Platinum-based anticancer drugs are most likely the most successful group of bioinorganic compounds. Their apparent disadvantages have led to the development of anticancer compounds of other noble metals, resulting in several ruthenium-based drugs which have entered clinical trials on oncological patients. Besides ruthenium, numerous rhodium complexes have been recently reported as highly potent antiproliferative agents against various human cancer cells, making them potential alternatives to Pt- and Ru-based metallodrugs. In this review, half-sandwich Rh(III) complexes are overviewed. Many representatives show higher in vitro potency than and different mechanisms of action (MoA) from the conventional anticancer metallodrugs (cisplatin in most cases) or clinically studied Ru drug candidates. Furthermore, some of the reviewed Rh(III) arenyl complexes are also anticancer in vivo. Pioneer anticancer organorhodium compounds as well as the recent advances in the field are discussed properly, and adequate attention is paid to their anticancer activity, solution behaviour and various processes connected with their MoA. In summary, this work summarizes the types of compounds and the most important biological results obtained in the field of anticancer half-sandwich Rh complexes. Full article

The relevance of multidimensional and porous crystalline materials to nuclear waste remediation and storage applications has motivated exploratory research focused on materials discovery of compounds, such as actinide mixed-oxoanion phases, which exhibit rich structural chemistry. The novel phase K_1.8Na_1.2[(UO₂)BSi₄O₁₂] has been synthesized using hydrothermal methods, representing the first example of a uranyl borosilicate. The three-dimensional structure crystallizes in the orthorhombic space group Cmce with lattice parameters a = 15.5471(19) Å, b = 14.3403(17) Å, c = 11.7315(15) Å, and V = 2615.5(6) ų, and is composed of UO₆ octahedra linked by [BSi₄O₁₂]⁵⁻ chains to form a [(UO₂)BSi₄O₁₂]³⁻ framework. The synthesis method, structure, results of Raman, IR, and X-ray absorption spectroscopy, and thermal stability are discussed. Full article

A mononuclear ruthenium complex, [Ru^II(L)(bpy)₂](PF₆), with a naphthoquinone-annelated imidazole ligand HL (2-(pyridin-2-yl)-1H-naphtho[2,3-d]imidazole-4,9-dione) was synthesized and structurally characterized. Electrochemical study reveals that the Ru complex shows four reversible redox waves at +0.98 V, −1.13 V, −1.53 V, and −1.71 V versus SCE in acetonitrile, which are assigned to Ru(II)/Ru(III), L⁻/L^•2−, and two bpy/bpy^•− redox couples, respectively. The redox potential of Ru(II)/Ru(III) was positively shifted upon the addition of trifluoromethanesulfonic acid due to protonation of the L⁻ moiety, leading to stabilization of the Ru 4d orbital. In UV-vis absorption measurements for the Ru complex in acetonitrile, a metal-to-ligand charge transfer (MLCT) band was observed at 476 nm, which was shifted to 450 nm by protonation, which might be due to a decrease in the electron delocalization and stabilization of the π orbitals in L⁻. The blue shift of the MLCT band by protonation was associated with a shift of an emission band from 774 nm to 620 nm, which could be caused by the decreased electronic delocalization in the MLCT excited state. These electrochemical and spectroscopic changes were reversible for the protonation/deprotonation stimuli. Full article

This work pertains to Cr³⁺ and Nd³⁺ co-activated Ca₂MgWO₆ phosphors synthesized by high temperature solid-state method using oxides and carbonates as raw materials. All luminescent samples according to Ca₂MgWO₆:Cr³⁺,Nd³⁺ include Cr³⁺ for the absorption of UV and visible radiation (230–800 nm) prior to energy transfer to Nd³⁺. As a result of the energy transfer between Cr³⁺ and Nd³⁺, we observe line emission originating from Nd³⁺ in the near infrared range additionally to the broad band near infrared emission from Cr³⁺ assigned to the spin-allowed ⁴T₂ → ⁴A₂ transition. The energy transfer from Cr³⁺ to Nd³⁺ is discussed via the variations of the lifetime data of Cr³⁺ and Nd³⁺. The strong absorption of Cr³⁺ in the ultraviolet range and the efficient energy transfer from Cr³⁺ to Nd³⁺ indicate that the herein presented material type can serve as a radiation converter for near infrared region light emitting diodes (NIR-LEDs) comprising an UV-A emitting (Al,Ga)N chip. Full article

Development of catalysts for the selective hydrolysis of proteins is challenging, yet important for many applications in biotechnology and proteomics. The hydrolysis of hydrophobic proteins is particularly challenging, as due to their poor solubility, the use of surfactants is often required. In this study, the proteolytic potential of catalyst systems based on the Zr(IV)-substituted Keggin polyoxometalate (Et₂NH₂)₁₀[Zr(PW₁₁O₃₉)₂] (Zr-K 1:2) and three different surfactants (ionic SDS (sodium dodecyl sulfate); zwitterionic Zw3-12 (n-dodecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate); and CHAPS (3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate)), which differ in structure and polarity, has been investigated. Hydrolysis of ovalbumin (OVA) was examined in the presence of Zr-K 1:2 and surfactants by sodium dodecyl sulfate poly(acrylamide) gel electrophoresis (SDS-PAGE), which showed the appearance of new polypeptide fragments at lower molecular weight, indicating that selective hydrolysis of OVA took place for all three catalyst systems. The same fragmentation pattern was observed, showing that the selectivity was not affected by surfactants. However, the surfactants influenced the performance of the catalyst. Hence, the interactions of OVA with surfactants and Zr-K 1:2 were investigated using different techniques such as tryptophan fluorescence, Circular Dichroism, and Dynamic Light Scattering. The speciation of the catalyst in surfactant solutions was also followed by ³¹P Nuclear Magnetic Resonance spectroscopy providing insight into its stability under reaction conditions. Full article

Multicompound TiO₂/SiO₂ nanoparticles with a diameter of 50–70 nm were generated using a liquid flame spray (LFS) nanoparticle deposition in a single flame. Here, we study the photocatalytic activity of deposited multicompound nanoparticles in gas-phase via oxidation of acetylene into carbon dioxide that gives new insight about the multicompound nanoparticle morphology. A small addition of SiO₂ content of 0.5%, 1.0% and 3.0% significantly suppressed the photocatalytic activity by 33%, 44% and 70%, respectively, whereas 5.0% SiO₂ addition completely removed the activity. This may be due to a formation of a thin passivating SiO₂ layer on top of the of the TiO₂ nanostructures during the LFS nanoparticle deposition. Surface wetting results support this hypothesis with a significant increase in water contact angle as the SiO₂ content is increased. Full article