A Highly Triflated Rare‐Earth Ion in [Eu(O3SCF3)8]5−

The reaction of Eu₂O₃ with fuming nitric acid, trifluormethanesulfonic acid, and its anhydride in torch‐sealed glass ampoules at 120 °C gave the europium compound (NO)₅[Eu(O₃SCF₃)₈] (orthorhombic, Fddd, Z=16, a=1932.69(4), b=2878.44(7), c=2955.12(7) pm, V=16439.7(7) ų). The compound exhibits the [Eu(O₃SCF₃)₈]^5? anion showing for the first time a lanthanide ion that is exclusively coordinated by eight triflate anions. The anion has been further investigated by DFT calculations, which also allowed clear assignment of the vibrational spectra. Moreover, magnetochemical and luminescence measurements gave additional insight into the properties of this complex. The luminescence spectra revealed that the Eu³⁺ ions are in a pseudo D_4d symmetric environment.     

Steric and Electronic Factors Associated with the Photoinduced Ligand Exchange of Bidentate Ligands Coordinated to Ru(II)

In an effort to create a molecule that can absorb low energy visible or near‐infrared light for photochemotherapy (PCT), the new complexes [Ru(biq)₂(dpb)](PF₆)₂ (1, biq = 2,2′‐biquinoline, dpb = 2,3‐bis(2‐pyridyl)benzoquinoxaline) and [(biq)₂Ru(dpb)Re(CO)₃Cl](PF₆)₂ (2) were synthesized and characterized. Complexes 1 and 2 were compared to [Ru(bpy)₂(dpb)](PF₆)₂ (3, bpy = 2,2′‐bipyridine) and [Ru(biq)₂(phen)](PF₆)₂ (4, phen = 1,10‐phenanthroline). Distortions around the metal and biq ligands were used to explain the exchange of one biq ligand in 4 upon irradiation. Complex 1, however, undergoes photoinduced dissociation of the dpb ligand rather than biq under analogous experimental conditions. Complex 3 is not photoactive, providing evidence that the biq ligands are crucial for ligand photodissociation in 1. The crystal structures of 1 and 4 are compared to explain the difference in photochemistry between the complexes. Complex 2 absorbs lower energy light than 1, but is photochemically inert although its crystal structure displays significant distortions. These results indicate that both the excited state electronic structure and steric bulk play key roles in bidentate photoinduced ligand dissociation. The present work also shows that it is possible to stabilize sterically hindered Ru(II) complexes by the addition of another metal, a property that may be useful for other applications.     

Functionalization of Liquid‐Exfoliated Two‐Dimensional 2H‐MoS2

Layered two‐dimensional (2D) inorganic transition‐metal dichalchogenides (TMDs) have attracted great interest as a result of their potential application in optoelectronics, catalysis, and medicine. However, methods to functionalize and process such 2D TMDs remain scarce. We have established a facile route towards functionalized layered MoS₂. We found that the reaction of liquid‐exfoliated 2D MoS₂, with M(OAc)₂ salts (M=Ni, Cu, Zn; OAc=acetate) yielded functionalized MoS₂–M(OAc)₂ materials. Importantly, this method furnished the 2H‐polytype of MoS₂ which is a semiconductor. X‐ray photoelectron spectroscopy (XPS), diffuse reflectance infrared Fourier transform spectroscopy (DRIFT–IR), and thermogravimetric analysis (TGA) provide strong evidence for the coordination of MoS₂ surface sulfur atoms to the M(OAc)₂ salt. Interestingly, functionalization of 2H‐MoS₂ allows for its dispersion/processing in more conventional laboratory solvents.     

Engineered L‐Serine Hydroxymethyltransferase from Streptococcus thermophilus for the Synthesis of α,α‐Dialkyl‐α‐Amino Acids

α,α‐Disubstituted α‐amino acids are central to biotechnological and biomedical chemical processes for their own sake and as substructures of biologically active molecules for diverse biomedical applications. Structurally, these compounds contain a quaternary stereocenter, which is particularly challenging for stereoselective synthesis. The pyridoxal‐5′‐phosphate (PLP)‐dependent L ‐serine hydroxymethyltransferase from Streptococcus thermophilus (SHMT_Sth; EC 2.1.2.1) was engineered to achieve the stereoselective synthesis of a broad structural variety of α,α‐dialkyl‐α‐amino acids. This was accomplished by the formation of quaternary stereocenters through aldol addition of the amino acids D ‐Ala and D ‐Ser to a wide acceptor scope catalyzed by the minimalist SHMT_Sth Y55T variant overcoming the limitation of the native enzyme for Gly. The SHMT_Sth Y55T variant tolerates aromatic and aliphatic aldehydes as well as hydroxy‐ and nitrogen‐containing aldehydes as acceptors.     

Na4IrO4: Square‐Planar Coordination of a Transition Metal in d5 Configuration due to Weak On‐Site Coulomb Interactions

Local environments and valence electron counts primarily determine the electronic states and physical properties of transition‐metal complexes. For example, square‐planar coordination geometries found in transition‐metal oxometalates such as cuprates are usually associated with the d⁸ or d⁹ electron configuration. In this work, we address an unusual square‐planar single oxoanionic [IrO₄]^4? species, as observed in Na₄IrO₄ in which Ir^IV has a d⁵ configuration, and characterize the chemical bonding through experiments and by ab initio calculations. We find that the Ir^IV center in ground‐state Na₄IrO₄ has square‐planar coordination geometry because of the weak Coulomb repulsion of the Ir‐5d electrons. In contrast, in its 3d counterpart Na₄CoO₄, the Co^IV center is tetrahedrally coordinated because of strong electron correlation. Na₄IrO₄ may thus serve as a simple yet important example to study the ramifications of Hubbard‐type Coulomb interactions on local geometries.     

Spectroscopic and Crystal Field Consequences of Fluoride Binding by [Yb⋅DTMA]3+ in Aqueous Solution

Yb?DTMA forms a ternary complex with fluoride in aqueous solution by displacement of a bound solvent molecule from the lanthanide ion. [Yb?DTMA?F]²⁺ and [Yb?DTMA?OH₂]³⁺ are in slow exchange on the relevant NMR timescale (<2000 s^?1), and profound differences are observed in their respective NMR and EPR spectra of these species. The observed differences can be explained by drastic modification of the ligand field states due to the fluoride binding. This changes the magnetic anisotropy of the Yb^III ground state from easy‐axis to easy‐plane type, and this change is easily detected in the observed magnetic anisotropy despite thermal population of more than just the ground state. The spectroscopic consequences of such drastic changes to the ligand field represent important new opportunities in developing fluoride‐responsive complexes and contrast agents.     

Reduction of Carbon Dioxide to Formate at Low Overpotential Using a Superbase Ionic Liquid

A new low‐energy pathway is reported for the electrochemical reduction of CO₂ to formate and syngas at low overpotentials, utilizing a reactive ionic liquid as the solvent. The superbasic tetraalkyl phosphonium ionic liquid [P₆₆₆₁₄][124Triz] is able to chemisorb CO₂ through equimolar binding of CO₂ with the 1,2,4‐triazole anion. This chemisorbed CO₂ can be reduced at silver electrodes at overpotentials as low as 0.17 V, forming formate. In contrast, physically absorbed CO₂ within the same ionic liquid or in ionic liquids where chemisorption is impossible (such as [P₆₆₆₁₄][NTf₂]) undergoes reduction at significantly increased overpotentials, producing only CO as the product.     

Magnetism and Afterglow United: Synthesis of Novel Double Core–Shell Eu2+-Doped Bifunctional Nanoparticles

Afterglow–magnetic nanoparticles (NPs) offer enormous potential for bioimaging applications, as they can be manipulated by a magnetic field, as well as emitting light after irradiation with an excitation source, thus distinguishing themselves from fluorescent living cells. In this work, a novel double core–shell strategy is presented, uniting co-precipitation with combustion synthesis routes to combine an Fe₃O₄ magnetic core (≈15 nm) with an afterglow SrAl₂O₄:Eu²⁺,Dy³⁺ outer coat (≈10 nm), and applying a SiO₂ protective middle layer (≈16 nm) to reduce the luminescence quenching caused by the Fe core ions. The resulting Fe₃O₄@SiO₂@SrAl₂O₄:Eu²⁺,Dy³⁺ NPs emit green light attributed to the 4f⁶5d¹→4f⁷(⁸S_7/2) transition of Eu²⁺ under UV radiation and for a few seconds afterwards. This bifunctional nanocomposite can potentially be applied for the detection and separation of cells or diagnostically relevant molecules.     

New Photosensitizers Based on Heteroleptic CuI Complexes and CO2 Photocatalytic Reduction with [NiII(cyclam)]Cl2

Earth-abundant metal complexes have been attracting increasing attention in the field of photo(redox)catalysis. In this work, the synthesis and full characterisation of four new heteroleptic Cu^I complexes are reported, which can work as photosensitizers. The complexes bear a bulky diphosphine (DPEPhos=bis[(2-diphenylphosphino)phenyl] ether) and a diimine chelating ligand based on 1-benzyl-4-(quinol-2′yl)-1,2,3-triazole. Their absorption has a relative maximum in the visible-light region, up to 450 nm. Thus, their use in photocatalytic systems for the reduction of CO₂ with blue light in combination with the known catalyst [Ni^II(cyclam)]Cl₂ was tested. This system produced CO as the main product through visible light (λ=420 nm) with a TON up to 8 after 4 hours. This value is in line with other photocatalytic systems using the same catalyst. Nevertheless, this system is entirely noble-metal free.     

Iodine(III)-catalyzed benzylic oxidation by using the (PhIO)n/Al(NO3)3 system

Abstract

The first iodine(III)-based procedure for the benzylic oxidation of different arenes is described by using the (PhIO)_n/Al(NO₃)₃ system under catalytic conditions leading to the formation of the corresponding carbonyl derivatives. The method proceeds under mild, operationally simple, room temperature, short reaction times, and open flask conditions. In light of the organocatalysis relevance and the novelty of our protocol, we wish to communicate our initial results of this novel oxidation.