Singlet oxygen generation as a major cause for parasitic reactions during cycling of aprotic lithium-oxygen batteries

Non-aqueous metal–oxygen batteries depend critically on the reversible formation/decomposition of metal oxides on cycling. Irreversible parasitic reactions cause poor rechargeability, efficiency, and cycle life, and have predominantly been ascribed to the reactivity of reduced oxygen species with cell components. These species, however, cannot fully explain the side reactions. Herewe showthat singlet oxygen forms at the cathode of a lithium–oxygen cell during discharge and from the onset of charge, and accounts for the majority of parasitic reaction products. The amount increases during discharge, early stages of charge, and charging at higher voltages, and is enhanced by the presence of tracewater. Superoxide and peroxide appear to be involved in singlet oxygen generation. Singlet oxygen traps and quenchers can reduce parasitic reactions effectively. Awareness of the highly reactive singlet oxygen in non-aqueous metal–oxygen batteries gives a rationale for future research towards achieving highly reversible cell operation

Synthesis of Fluorine-18 Functionalized Nanoparticles for use as in vivo Molecular Imaging Agents

Nanoparticles containing fluorine-18 were prepared from block copolymers made by ring opening metathesis polymerization (ROMP). Using the fast initiating ruthenium metathesis catalyst (H_2IMes)(pyr)_2(Cl)_2Ru=CHPh, low polydispersity amphiphilic block copolymers were prepared from a cinnamoyl-containing hydrophobic norbornene monomer and a mesyl-terminated PEG-containing hydrophilic norbornene monomer. Self-assembly into micelles and subsequent cross-linking of the micelle cores by light-activated dimerization of the cinnamoyl groups yielded stable nanoparticles. Incorporation of fluorine-18 was achieved by nucleophilic displacement of the mesylates by the radioactive fluoride ion with 31% incorporation of radioactivity. The resulting positron-emitting nanoparticles are to be used as in vivo molecular imaging agents for use in tumor imaging

cis-Dichlorido(1,3-dimesitylimidazolidin-2-yl­idene)(2-formyl­benzyl­idene-κ2 C,O)ruthenium diethyl ether solvate

The title compound, [RuCl2(C8H6O)(C21H26N2)]·C4H10O, contains a catalytically active ruthenium carbene complex of the ‘second-generation Grubbs/Hoveyda’ type with Ru in a square-pyramidal coordination, the apex of which is formed by the benzyl­idene carbene atom with Ru=C 1.827 (2) Å. The complex shows the uncommon cis, rather than the usual trans, arrangement of the two chloride ligands, with Ru—Cl bond lengths of 2.3548 (6) and 2.3600 (6) Å, and a Cl—Ru—Cl angle of 89.76 (2)°. This cis configuration is desirable for certain applications of ring-opening metathesis polymerization (ROMP) of strained cyclic olefins. The crystalline solid is a diethyl ether solvate, which is built up from a porous framework of Ru complexes held together by π–π stacking and C—H⋯Cl and C—H⋯O inter­actions. The disordered diethyl ether solvent mol­ecules are contained in two independent infinite channels, which extend parallel to the c axis at x,y = 0,0 and x,y = , and have solvent-accessible void volumes of 695 and 464 Å3 per unit cell

Combining Brillouin Light Scattering Spectroscopy and Machine-Learned Interatomic Potentials to Probe Mechanical Properties of Metal-Organic Frameworks.

The mechanical properties of metal-organic frameworks (MOFs) are of high fundamental and practical relevance. A particularly intriguing technique for determining anisotropic elastic tensors is Brillouin scattering, which so far has rarely been used for highly complex materials like MOFs. In the present contribution, we apply this technique to study a newly synthesized MOF-type material, referred to as GUT2. The experiments are combined with state-of-the-art simulations of elastic properties and phonon bands, which are based on machine-learning force fields and dispersion-corrected density functional theory. This provides a comprehensive understanding of the experimental signals, which can be correlated to the longitudinal and transverse sound velocities of the material. Notably, the combination of the insights from simulations and experiments allows the determination of approximate values for the components of the elastic tensor of the studied material even when dealing with comparably small single crystals, which limit the range of accessible experimental data

Role of Filler Content and Morphology in LLZO/PEO Membranes

publishedVersio

Reactions of (polypyrazolylborato)(benzonitrile)rutheniums with terminal alkynes: Reactivity changeover by triethylamine toward arylalkyne polymerization or formation of (arylmethyl)(carbonyl) complexes

Reactions of (κ 3-polypyrazolylborato)(benzonitrile) rutheniums [RuCl{B(4-Ypz) 4}(PhCN) 2] {4-Ypz; 4-bromo-1-pyrazolyl (Y = Br) and 1-pyrazolyl (Y = H) groups} with terminal alkynes were studied. For the reactions with arylalkynes HC≡C(aryl) in the presence of NEt 3, (arylmethyl)(carbonyl)rutheniums [Ru{CH 2(aryl)}{B(4-Ypz) 4}(CO)(PhCN)] were yielded, indicating alkyne C≡C bond cleavage, whereas in the absence of NEt 3, arylalkyne polymerization proceeded instead of the (arylmethyl)ruthenium formation. Reasonably attributed reaction mechanism shows significant role of the vinylidene intermediates "Ru=C=CH(aryl)"

(Benzonitrile-κN)chlorido[hydrido­tris(pyrazol-1-yl-κN 2)borato](triphenyl­phosphine-κP)ruthenium(II) ethanol solvate

The reaction of [Ru(C9H10BN6)Cl(C18H15P)2] with benzo­nitrile leads to crystals of the title compound, [Ru(C9H10BN6)Cl(C18H15P)(C7H5N)]·C2H5OH. In the crystal structure, the environment about the ruthenium metal center corresponds to a slightly distorted octa­hedron with an average N—Ru—N bite angle of the Tp ligand of 86.6 (2)°

(Benzophenone imine-κN)­chlorido(hydrido­tripyrazolyl­borato)­(triphenyl­phosphine)ruthenium(II) diethyl ether solvate

The reaction of RuCl(Tp)(Ph3P)2, where Tp is [(CH)3N2]3BH, with benzophenone imine leads to the formation of the title compound, [Ru(C9H10BN6)Cl(C13H11N)(C18H15P)]·C4H10O. The environment about the Ru atom corresponds to a slightly distorted octa­hedron and the bite angle of the Tp ligand produces an average N—Ru—N angle of 86.3 (9)°. The three Ru—N(Tp) bond lengths [2.117 (2), 2.079 (2) and 2.084 (2) Å] are slightly longer than the average distance (2.038 Å) in other ruthenium–Tp complexes

Chlorido[hydridotris(pyrazol-1-yl-κN 2)borato](1H-pyrazole-κN 2)(triphenyl­phosphine-κP)ruthenium(II)

In the title compound, [Ru(C9H10BN6)Cl(C3H4N2)(C18H15P)], the RuII atom is coordinated by an N,N′,N′′-tridentate hydrido­trispyrazolylborate (Tp) ligand, a pyrazole (HPz) mol­ecule, a chloride ion and a triphenyl­phosphine ligand, resulting in a distorted RuClPN4 octa­hedral coordination for the metal ion: the tridentate N atoms occupy one octa­hedral face and the Cl and P atoms are cis. One of the phenyl rings is disordered over two orientations in a 0.547 (10):0.453 (10) ratio, and a weak intra­molecular N—H⋯Cl hydrogen bond generates an S(5) ring

Singlet oxygen from cation driven superoxide disproportionation and consequences for aprotic metal-O2 batteries

Aprotic alkali metal-oxygen batteries require reversible formation of metal superoxide or peroxide on cycling. Severe parasitic reactions cause poor rechargeability, efficiency, and cycle life and have been shown to be caused by singlet oxygen (1O2) that forms at all stages of cycling. However, its formation mechanism remains unclear. We show that disproportionation of superoxide, the product or intermediate on discharge and charge, to peroxide and oxygen is responsible for 1O2 formation. While the overall reaction is driven by the stability of peroxide and thus favored by stronger Lewis acidic cations such as Li+, the 1O2 fraction is enhanced by weak Lewis acids such as organic cations. Concurrently, the metal peroxide yield drops with increasing 1O2. The results explain a major parasitic pathway during cell cycling and the growing severity in K-, Na-, and Li-O2 cells based on the growing propensity for disproportionation. High capacities and rates with peroxides are now realized to require solution processes, which form peroxide or release O2via disproportionation. The results therefore establish the central dilemma that disproportionation is required for high capacity but also responsible for irreversible reactions. Highly reversible cell operation requires hence finding reaction routes that avoid disproportionation