Hybrid Plasmonic–Aerogel Materials as Optical Superheaters with Engineered Resonances

Solar radiation is a versatile source of energy, convertible to different forms of power. A direct path to exploit it is the generation of heat, for applications including passive building heating, but it can also drive secondary energy-conversion steps. We present a novel concept for a hybrid material which is both strongly photo-absorbing and with superior characteristics for the insulation of heat. The combination of that two properties is rather unique, and make this material an optical superheater. To realize such a material, we are combining plasmonic nanoheaters with alumina aerogel. The aerogel has the double function of providing structural support for plasmonic nanocrystals, which serve as nanoheaters, and reducing the diffusion rate of the heat generated by them, resulting in large local temperature increases under a relatively low radiation intensity. This work includes theoretical discussion on the physical mechanisms impacting the system's balanced thermal equilibrium.     

Heterobimetallic Cuprates Consisting of a Redox‐Switchable,Silicon‐Based Metalloligand: Synthesis,Structures, and Electronic Properties

A series of bimetallic silyl halido cuprates consisting of the new tripodal silicon‐based metalloligand [κ³N‐Si(3,5‐Me₂pz)₃Mo(CO)₃]^? is presented (pz=pyrazolyl). This metalloligand is straightforwardly accessible by reacting the ambidentate ligand tris(3,5‐dimethylpyrazolyl)silanide ({Si(3,5‐Me₂pz)₃}^?) with [Mo(CO)₃(η⁶‐toluene)]. The compound features a fac‐coordinated tripodal chelating ligand and an outward pointing, “free” pyramidal silyl donor, which is easily accessible for a secondary coordination to other metal centers. Several bimetallic silyl halido cuprates of the general formula [CuX{μ‐κ¹Si:κ³N‐Si(3,5‐Me₂pz)₃Mo(CO)₃}]^? (X=Cl, Br, I) have been synthesized. The electronic and structural properties of these complexes were probed in detail by X‐ray diffraction analysis, electrospray mass spectrometry, infrared‐induced multiphoton dissociation studies, cyclic voltammetry, spectroelectrochemistry, gas‐phase photoelectron spectroscopy, as well as UV/Vis and fluorescence spectroscopy. The heterobimetallic complexes contain linear two‐coordinate copper(I) entities with the shortest silicon–copper distances reported so far. Oxidation of the anionic complexes in methylene chloride and acetonitrile solutions at ${E{{0\hfill \atop 1/2\hfill}}}$ =?0.60 and ?0.44 V (vs. ferrocene/ferrocenium (Fc/Fc⁺)), respectively, shows substantial reversibility. Based on various results obtained from different characterization methods, as well as density functional theory calculations, these oxidation events were attributed to the Mo⁰/Mo^I redox couple.     

Dibutylsilylene Derivatives of Tartaric Acid

Crystals of the bis(tert‐butyl)silylene (DTBS) derivatives of the tartaric acids were synthesized from D ‐, L ‐, rac‐, and meso‐tartaric acid and DTBS bis(trifluoromethanesulfonate): two polymorphs of Si₂tBu₄(L ‐Tart1,2;3,4H_–4) (L ‐ 1a and L ‐ 1b ), the mirror image of the denser modification (D ‐ 1b ) as well as the racemate ( 2 ), and the meso analogue Si₂tBu₄(meso‐Tart1,3;2,4H_–4) ( 3 ). The structures were determined by single‐crystal X‐ray diffraction. The threo‐configured D ‐ and L ‐ (and rac‐) tartrates were coordinated by two tBu₂Si units forming five‐membered chelate rings, whereas the erythro‐configured meso‐tartrate formed six‐membered chelate rings. The new compounds were analyzed by NMR techniques, including ²⁹Si NMR spectroscopy, and single‐crystal X‐ray crystallography.     

Chemo- and Site-Selective Electro-Oxidative Alkane Fluorination by C(sp3)−H Cleavage

Electrochemical fluorinations of C(sp³)−H bonds with a nucleophilic fluoride source have been accomplished in a chemo- and site-selective fashion, avoiding the use of electrophilic F⁺ sources and stoichiometric oxidants. The introduced metal-free strategy exhibits high functional group tolerance, setting the stage for late-stage fluorinations of biorelevant motifs. The synthetic utility of the C(sp³)−H fluorination was reflected by subsequent one-pot arylation of the generated benzylic fluorides.     

Bistriazoles Connected Through a B−B Bridge,Synthesized by Highly Selective Dipolar Cycloaddition Reactions of a Diazido-diborane(4)

In this work we report the first cycloaddition reactions between a diazido diborane(4) and terminal alkynes, providing unique access to bis-1,2,3-triazoles connected by a B−B bridge. The catalyst-free reactions are highly selective, yielding exclusively the thermodynamically disfavored bis-1,4-triazoles. The reactions are enabled by the high thermal stability of the diazido-diborane [B(hpp)(N₃)]₂ (hpp=1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-α]pyrimidinate). Due to the tetra-coordinate boron atoms in this reagent, the reactions are tolerant with respect to the introduction of Lewis-basic groups at the alkyne. The scope and limitations of the new reactions are discussed.     

Sodiation Of Hard Carbon: How Separating Enthalpy And Entropy Contributions Can Find Transitions Hidden In The Voltage Profile

Sodium-ion batteries (NIBs) utilize cheaper materials than lithium-ion batteries (LIBs) and can thus be used in larger scale applications. The preferred anode material is hard carbon, because sodium cannot be inserted into graphite. We apply experimental entropy profiling (EP), where the cell temperature is changed under open circuit conditions. EP has been used to characterize LIBs; here, we demonstrate the first application of EP to any NIB material. The voltage versus sodiation fraction curves (voltage profiles) of hard carbon lack clear features, consisting only of a slope and a plateau, making it difficult to clarify the structural features of hard carbon that could optimize cell performance. We find additional features through EP that are masked in the voltage profiles. We fit lattice gas models of hard carbon sodiation to experimental EP and system enthalpy, obtaining: 1. a theoretical maximum capacity, 2. interlayer versus pore filled sodium with state of charge.     

Ionothermal Synthesis of Sulfidobismuth spiro-Dicubane Cations

Bi₂S₃ was dissolved in the presence of NaCl in the ionic liquid [BMIm]Cl ⋅ 4AlCl₃ (BMIm=1-n-butyl-3-methylimidazolium) through annealing the mixture at 180 °C. Upon cooling to room temperature, orange, air-sensitive crystals of Na(Bi₇S₈)[S(AlCl₃)₃]₂[AlCl₄]₂ ( 1 ) precipitated. X-ray diffraction on single-crystals of 1 revealed a triclinic crystal structure that contains (Bi₇S₈)⁵⁺ spiro-dicubanes, [S(AlCl₃)₃]²⁻ tetrahedra triples, isolated [AlCl₄]⁻ tetrahedra, and sodium cations.     

Speciation of Copper(II)-Betaine Complexes as Starting Point for Electrochemical Copper Deposition from Ionic Liquids

The application of ionic liquids for the dissolution of metal oxides is a promising field for the development of more energy- and resource-efficient metallurgical processes. Using such solutions for the production of valuable chemicals or electrochemical metal deposition requires a detailed understanding of the chemical system and the factors influencing it. In the present work, several compounds are reported that crystallize after the dissolution of copper(II) oxide in the ionic liquid [Hbet][NTf₂]. Dependent on the initial amount of chloride, the reaction temperature and the purity of the reagent, copper crystallizes in complexes with varying coordination geometries and ligands. Subsequently, the influence of these different complex species on electrochemical properties is shown. For the first time, copper is deposited from the ionic liquid [Hbet][NTf₂], giving promising opportunities for more resource-efficient copper plating. The copper coatings were analyzed by SEM and EDX measurements. Furthermore, a mechanism for the decomposition of [Hbet][NTf₂] in the presence of chloride is suggested and supported by experimental evidence.