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We characterize the double-faced nature of hydrogen bonding in hydroxy-functionalized ionic liquids by means of neutron diffraction with isotopic substitution (NDIS), molecular dynamics (MD) simulations, and quantum chemical calculations. NDIS data are fit using the empirical potential structure refinement technique (EPSR) to elucidate the nearest neighbor H⋅⋅⋅O and O⋅⋅⋅O pair distribution functions for hydrogen bonds between ions of opposite charge and the same charge. Despite the presence of repulsive Coulomb forces, the cation-cation interaction is stronger than the cation-anion interaction. We compare the hydrogen-bond geometries of both "doubly charged hydrogen bonds" with those reported for molecular liquids, such as water and alcohols. In combination, the NDIS measurements and MD simulations reveal the subtle balance between the two types of hydrogen bonds: The small transition enthalpy suggests that the elusive like-charge attraction is almost competitive with conventional ion-pair formation., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The existence of [μ-HSi 4 ] 3- in liquid ammonia solutions is confirmed by 1 H and 29 Si NMR experiments. Both NMR and quantum chemical calculations reveal that the H atom bridges two Si atoms of the [Si 4 ] 4- cluster, contrary to the expectation that it is located at one vertex Si of the tetrahedron. The calculations also indicate that in the formation of [μ-HSi 4 ] 3- , protonation is driven by a high charge density and an increase of electron delocalization compared to [Si 4 ] 4- . Additionally, [Si 5 ] 2- was detected for the first time and characterized by NMR. Calculations show that it is resistant to protonation, owing to a strong charge delocalization, which is significantly reduced upon protonation. Thus, our methods reveal three silicides in liquid ammonia: unprotonated [Si 5 ] 2- , terminally protonated [HSi 9 ] 3- , and bridge-protonated [μ-HSi 4 ] 3- . The protonation trend can be roughly predicted by the difference in charge delocalization between the parent compound and the product, which can be finely tuned by the presence of counter ions in solution., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

We report on the first unambiguous detection of the elusive [HSi 9 ] 3- anion in solutions of liquid ammonia by various 29 Si and 1 H NMR experiments including chemical exchange saturation transfer (CEST). The characteristic multiplicity patterns of both the 29 Si and 1 H resonances together with CEST and a partially reduced 1 H, 29 Si coupling constant indicate the presence of a highly dynamic Si 8 entity and a Si-H moiety with slow proton hopping. Theoretical calculations corroborate both reorganization of Si 8 on the picosecond timescale via low vibrational modes and proton hopping. In addition, in a single-crystal X-ray study of (K(DB[18]crown-6))(K([2.2.2]crypt)) 2 [HSi 9 ]⋅8.5 NH 3 , the H atom was unequivocally localized at one vertex of the basal square of the monocapped square-antiprismatic cluster. Thus experimental studies and theoretical considerations provide unprecedented insight into both the structure and the dynamic behavior of these cluster anions, which hitherto had been considered to be rigid., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Although the chemistry of transition metal polyphosphide anions has attracted significant attention, there are few reports of studies in which such species have been synthesized directly from white phosphorus. [K(OEt 2 ) 2 {Co(BIAN)(cod)}] (1, BIAN=1,2-bis(2,6-diisopropylphenylimino)acenaphthene, cod=1,5-cyclooctadiene), which is readily prepared by ligand exchange from [K(thf) x {Co(cod) 2 }], reacts with P 4 to afford [{K(thf)} 2 {(BIAN)Co} 2 (μ-η 4 :η 4 -P 4 )] (2 a) in 61 % yield (isolated product). [{K(OEt 2 )} 2 {(BIAN)Co} 2 (μ-η 4 :η 4 -P 4 )] (2 b) and [K([18]crown-6)(MeCN)] 2 [{(BIAN)Co} 2 (μ-η 4 :η 4 -P 4 )] (2 c) were obtained by recrystallizing 2 a from diethyl ether and acetonitrile (and using [18]crown-6 in case of 2 c). Oxidation of 2 a with [Cp 2 Fe]BAr F 4 (one equivalent) and subsequent recrystallization of the product from different solvents gave [K(OEt 2 ){(BIAN)Co} 2 (μ-η 4 :η 4 -P 4 )] (3 a) and [K(dme) 4 ][{(BIAN)Co} 2 (μ-η 4 :η 4 -P 4 )] (3 b; dme=1,2-dimethoxyethane). Neutral [{(BIAN)Co} 2 (μ-η 4 :η 4 -P 4 )] (4) was obtained in moderate yield by oxidizing 2 a with two equivalents of [Cp 2 Fe]BAr F 4 . The new complexes were characterized by NMR, EPR (in the case of 3 a), and UV/Vis spectroscopy, and elemental analysis. The molecular structures revealed by X-ray crystallography display planar cyclic or open-chain P 4 4- units sandwiched between {(BIAN)Co} fragments., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A fullerene was covalently attached to a (dA)20 template that serves as structural scaffold to self-assemble an ordered and mixed array of ethynyl-pyrene- and ethynyl-Nile-red-nucleoside conjugates. Fluorescence spectroscopy revealed evidence for energy transfer between the two different chromophores. Moreover, fluorescence quenching is significantly enhanced by the attached fullerene in mixed assemblies of different chromophore ratios. This indicates exciton dissociation by electron transfer from the photo-generated exciton on the chromophore stack to the fullerene. The fullerene-DNA-conjugate was integrated as a photo-active layer in solar cells that showed charge-carrier generation in the spectral regime of all three components of the conjugate. This work clearly demonstrates that DNA is suitable as structural element for chromophore assemblies in future organic optoelectronic devices, such as solar cells., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Homoatomic polyanions of post-transition main-group metals, namely, Zintl anions, are precast in analogous Zintl phases and can react in solution to form new materials. Despite comprehensible reaction approaches, the formed products cannot be planned in advance, as hitherto undetected and therefore disregarded side reactions take place. The outcomes and interpretations of the reactions of Zintl anions are so far based mainly on crystal structures, which only allow characterization of the product that has the lowest solubility. Here we present the results of our investigation of the stability of highly charged tin Zintl anions in liquid ammonia, which is not exclusively based on solution effects but also on the oxidative influence of the solvent. This allows for a deeper understanding of the ongoing processes in solution and opens doors to the directed synthesis of transition metal complexes of Sn4 (4-) , here shown by its reactivity towards MesCu., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Photo-active layers from non-stabilized P3HT:ICBA nanoparticles enable the fabrication of inverted organic solar cells from eco-friendly, alcoholic dispersions. Exhibiting power conversion efficiencies (PCEs) ≈4%, the devices are competitive to state-of-the-art P3HT:ICBA solar cells from chlorinated solvents. Upon thermal annealing, the short circuit current density and consequently the PCE of the inverted solar cells improve radically due to a more intimate contact of the nanoparticles and hence an enhanced charge carrier extraction., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The title of this article is the motto of the fourth meeting of the Intergovernmental Forum on Chemical Safety (Forum IV), which is to be held in Bangkok in November 2003. The IFCS has been in existence for 10 years. During this period politicians, scientists, and the general public have become increasingly aware of the risks associated with chemicals. International conventions providing for prohibitions and restrictions of dangerous chemicals, and for better control of trade have been set up. These conventions will soon be binding under international law. In developing countries many people who handle or use hazardous chemicals are illiterate or poorly educated; they may not fully understand what they are handling. The industrialized countries therefore have a special duty to incorporate chemical safety in development cooperation measures. Through their presence at this year's forum, prominent chemists such as Carl Djerassi will seek to underline the fact that a long term preventive approach to healthcare and the environment is only possible through international cooperation. This overview describes current developments in the field of chemical safety policy and presents a selection of the legislation currently in force for chemicals in the European Union. It also provides an insight into the interwoven structure of international cooperation that takes place at both the political and the technical level.

The biological effects of the potent inflammatory mediator C5a, a complement split product, on human neutrophils and monocytes are limited by the rapid internalization of its specific receptor (C5aR, CD88). The C terminus of the C5aR is phosphorylated after stimulation with C5a of phorbol ester, and this phosphorylation might lead to receptor internalization. In this context, we have studied the effects on C5aR internalization of C5a, phorbol 12-myristate 13-acetate (PMA), the protein kinase inhibitor staurosporine, and pertussis toxin on rat basophilic RBL.2H3 cells stably transfected with the human wild-type or mutant C5aR. C5aR mutants lacked either part of the cytosolic C terminus, including suggested major phosphorylation sites, or a putative phosphorylation motif for protein kinase C in the third cytosolic loop. Additionally, agonist-induced internalization was analyzed on HEK293 cells co-transfected with C5aR and the pertussis toxin-resistant G protein alpha subunit, G alpha 16. Staurosporine-sensitive agonist-dependent C5aR internalization could be detected, suggesting that C5aR phosphorylation, most likely of the C terminus, participates in this type of internalization. In contrast, PMA-induced C5aR internalization seems to be independent of putative phosphorylation sites in either the truncated section of the C terminus or the third cytosolic loop. The phorbol ester-induced C5aR internalization may, therefore, be caused by an indirect and less specific effect of protein kinase C on the internalization machinery. Manipulation of the pertussis toxin-sensitive or -resistant G protein-dependent signal transduction had no effect on ligand-induced internalization.