Early–Late Heterometallic Complexes of Gold and Zirconium: Photoluminescence and Reactivity

OH functionalized triarylphosphines were used to assemble zirconocene‐based metalloligands with phosphine donor sites in varying positions. These complexes were subsequently treated with different gold precursors to obtain early–late heterometallic compounds in which the metal atoms exhibit different intermetallic distances. All compounds were fully investigated by spectroscopic techniques, photoluminescence measurements and single crystal X‐ray diffraction. Quantum chemical calculations were also performed. Some compounds show bright emission even at room temperature with quantum yields of up to 19 % (excitation at 350 nm). Furthermore, the reactivity of dimethyl zirconocene derivatives towards gold complexes was investigated, revealing simultaneous ligand exchange and transmetallation reactions.     

Mechanical and shape‐memory properties of poly(mannitol sebacate)/cellulose nanocrystal nanocomposites

Polyesters based on polyols and sebacic acid, known as poly(polyol sebacate)s (PPS), are attracting considerable attention, as their properties are potentially useful in the context of soft‐tissue engineering applications. To overcome the drawback that PPSs generally display rather low strength and stiffness, we have pursued the preparation of nanocomposites based poly(mannitol sebacate) (PMS), a prominent example of this materials family, with cellulose nanocrystals (CNCs). Nanocomposites were achieved in a two‐step process. A soluble, low‐molecular‐weight PMS pre‐polymer was formed via the polycondensation reaction between sebacic acid and D‐mannitol. Nanocomposites with different CNC content were prepared by solution‐casting and curing under vacuum using two different profiles designed to prepare materials with low and high degree of crosslinking. The as‐prepared nanocomposites have higher stiffness and toughness than the neat PMS matrix while maintaining a high elongation at break. A highly crosslinked nanocomposite with a CNC content of 5 wt % displays a sixfold increase in Young's modulus and a fivefold improvement in toughness. Nanocomposites also exhibit a shape memory effect with a switch temperature in the range of 15 to 45 °C; in particular the materials with a thermal transition in the upper part of this range are potentially useful for biomedical applications. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3123–3133     

Thermodynamic Properties of Aqueous Glucose–Urea–Salt Systems

In this work, the thermodynamic behavior of aqueous solutions containing the solutes NaCl, glucose, and/or urea is investigated. These substances are vital components for living bodies and further they are main components of blood serum. Osmotic coefficients were determined by cryoscopic measurements in single-solute and multi-solute aqueous solutions containing salts (NaCl, KCl, CaCl₂), glucose, and/or urea. The results show that NaCl determines the osmotic coefficients in the urea/glucose/NaCl/water system. Investigation of the effect of different salts on osmotic coefficients revealed ion-specific effects. At physiologically important solute concentrations in typical blood serum solutions, the osmotic coefficients were found to be in the range of 0.90–0.93. In a second step, the state of water in different glucose/salt/water and urea/salt/water systems was investigated. Depending on the kind of salt, the chemical potential of water in urea/salt/water is either higher or lower than in glucose/salt/water systems at equal nonelectrolyte concentrations. This result was found to be independent of the salt molality. Finally, the investigated systems were modeled with the Pitzer model and the ePC-SAFT equation of state, which allowed predicting of the properties of these multi-solute aqueous solutions.     

Novel Addition of Diphosphanes to Carbonyl Compounds

During our attempts to synthesize chiral bidentate bis(trifluoromethyl)phosphane containing ligands, we found a bis(trifluoromethyl)phosphanide induced formal insertion of acetone into tetrakis(trifluoromethyl)diphosphane.     

Intramolecular Diastereoselective Cascade Cyclization Reaction of N,N′-Bis(Salicylidene)Cyclohexanediimine with Phosphoryltrichloride to a Bis(Chlorophosphorylated) Decahydro-2,4-DI (2-Hydroxyphenyl)Benzo[d][1,3,6]oxadiazepine

Abstract

A new type of cascade cyclization was observed in the phosphorylation reaction of (R,R)- or (S,S)-N,N′-bis(salicylidene)cyclohexanediimine with phosphoryltrichloride, which resulted in the formation of bis(chlorophosphorylated) decahydro-2,4-di(2-hydroxyphenyl)benzo[d][1,3,6]oxadiazepine with two new stereogenic phosphorus atoms and two new stereogenic carbon atoms in the oxadiazepine ring in the β-position to phosphorus. During the synthesis, the N atom attacks the phosphorodichloridate group with the formation of the P–N bond to give an asymmetric phosphorus atom and an iminium ion. This compound with six stereogenic centers crystallizes in the monoclinic centrosymmetric space group P2₁/c and the crystal structure together with solution and solid-state MAS ¹³C and ³¹P NMR studies reveals a preferential formation of stereoisomers.     

Enhancing the Variability of [Ge9] Cluster Chemistry through Phosphine Functionalization

The synthetic approach towards molecules that contain Ge atoms with oxidation state 0, and which are exclusively connected to other Ge atoms, is explored by using anionic clusters extracted from binary solids. Besides providing a novel variable method for the introduction of alkenyl moieties to [Ge₉] cluster compounds, this work expands the spectrum of mixed-functionalized [Ge₉] cluster anions, which are suitable for the straightforward synthesis of zwitterionic compounds upon coordination to metal cations. In detail, the synthesis of a series of mixed-functionalized [Ge₉] clusters is reported, including [Ge₉{Si(TMS)₃}₃PRR^I] (R=tBu, R^I=(CH₂)₃CH=CH₂; 2 ) and [Ge₉{Si(TMS)₃}₂PRR^I]⁻ (R and R^I: alkyl, alkenyl, aryl, aminoalkyl; 3 a to 11 a , TMS: (trimethyl)silyl). In 2 and 3 a , pentenyl functionalization of the [Ge₉] clusters was achieved by reaction of the novel chlorophosphine tBu{(CH₂)₃CH=CH₂}PCl ( 1 ) with silylated [Ge₉] clusters. Furthermore, the reactivity of the cluster anions 3 a to 11 a towards NHC^DippMCl (NHC^Dipp=1,3-di(2,6-diisopropylphenyl)imidazolylidine; M=Cu, Ag) showed a dependency on the steric demand of the phosphine either zwitterions ( 3 -MNHC^Dipp to 7 -MNHC^Dipp) featuring P–M interactions are formed, or Ge–M coordination ( 8 -MNHC^Dipp to 11 -MNHC^Dipp) occurs. For M=Ag, the formation of zwitterionic complexes was unequivocally proven by NMR investigations showing ¹J(³¹P-¹⁰⁷Ag/¹⁰⁹Ag) spin-spin coupling.     

Clarification of Decomposition Pathways in a State-of-the-Art Lithium Ion Battery Electrolyte through 13C-Labeling of Electrolyte Components

The decomposition of state-of-the-art lithium ion battery (LIB) electrolytes leads to a highly complex mixture during battery cell operation. Furthermore, thermal strain by e.g., fast charging can initiate the degradation and generate various compounds. The correlation of electrolyte decomposition products and LIB performance fading over life-time is mainly unknown. The thermal and electrochemical degradation in electrolytes comprising 1 m LiPF₆ dissolved in ¹³C₃-labeled ethylene carbonate (EC) and unlabeled diethyl carbonate is investigated and the corresponding reaction pathways are postulated. Furthermore, a fragmentation mechanism assumption for oligomeric compounds is depicted. Soluble decomposition products classes are examined and evaluated with liquid chromatography-high resolution mass spectrometry. This study proposes a formation scheme for oligo phosphates as well as contradictory findings regarding phosphate-carbonates, disproving monoglycolate methyl/ethyl carbonate as the central reactive species.     

Consequences of the One‐Electron Reduction and Photoexcitation of Unsymmetric Bis‐imidazolium Salts

Coupling of uronium salts with in situ generated N‐heterocyclic carbenes provides straightforward access to symmetrical [ 4 ]²⁺ and unsymmetrical bis‐imidazolium salts [ 6 ]²⁺ and [ 9 ]²⁺. As indicated by cyclic and square‐wave voltammetry, [ 6 ]²⁺ and [ 9 ]²⁺ can be (irreversibly) reduced by one electron. The initially formed radicals [ 6 ]^.+ and [ 9 ]^.+ undergo further reactions, which were probed by EPR spectroscopy and density functional calculations. The final products of the two‐electron reduction are the two carbenes. Upon irradiation with UV light both [ 6 ]²⁺ and [ 9 ]²⁺ emit at room temperature in solution but with dramatically different characteristics. The different fluorescence behavior is analyzed by emission spectroscopy and interpreted by using time‐dependent density functional calculations as largely due to different excited‐state dynamics of [ 6 ]²⁺ and [ 9 ]²⁺. The geometries of both radicals [ 6 ]^.+ and [ 9 ]^.+ and excited states {[ 6 ]²⁺} * and {[ 9 ]²⁺}* are substantially different from those of the parent ground‐state molecules.