No abstract

Kryptopyrrole (2,4-dimethyl-3-ethylpyrrole) was acylated with, for example, benzoyl chloride to afford 2-benzoyl-3,5-dimethyl-4-ethylpyrrole (L(1)H). With SiCl4 this ligand reacts under liberation of HCl and formation of the complex L(1)2SiCl2. In related reactions with HSiCl3 or H2SiCl2, the same chlorosilicon complex is formed under liberation of HCl and H2 or liberation of H2, respectively. The chlorine atoms of L(1)2SiCl2 can be replaced by fluoride and triflate using ZnF2 and Me3Si-OTf, respectively. The use of a supporting base (triethylamine) is required for the complexation of phenyltrichlorosilane and diphenyldichlorosilane. The complexes L(1)2SiCl2, L(1)2SiF2, L(1)2Si(OTf)2, L(1)2SiPhCl, and L(1)2SiPh2 exhibit various configurations of the octahedral silicon coordination spheres (i.e. cis or trans configuration of the monodentate substituents, different orientations of the bidentate chelating ligands relative to each other). Furthermore, cationic silicon complexes L(1)3Si(+) and L(1) SiPh(+) were synthesized by chloride abstraction with GaCl3. In contrast, reaction of L(1)2SiCl2 with a third equivalent of L(1)H in the presence of excess triethylamine produced a charge-neutral hexacoordinate Si complex with a new tetradentate chelating ligand which formed by Si-templated C-C coupling of two ligands L(1).

The first examples of silicon compounds of 1,1-bis­(pyrrol-2-yl)­ethenes have been synthesized via salt metathesis from a 2-fold lithiated dipyrromethene and different diorganodichlorosilanes (i.e., dimethyldichlorosilane, diphenyldichlorosilane, and 1,1-dichlorosilacyclobutane). Herein we report on their molecular structures, their optical properties, and some reactivity patterns.

Due to their beneficial properties, the use of zinc oxide nanoparticles (ZnO NP) is constantly increasing, especially in consumer-related areas, such as food packaging and food additives, which is leading to an increased oral uptake of ZnO NP. Consequently, the aim of our study was to investigate the cellular uptake of two differently sized ZnO NP (<50 nm and <100 nm; 12–1229 µmol/L) using two human intestinal cell lines (Caco-2 and LT97) and to examine the possible resulting toxic effects. ZnO NP (<50 nm and <100 nm) were internalized by both cell lines and led to intracellular changes. Both ZnO NP caused time- and dose-dependent cytotoxic effects, especially at concentrations of 614 µmol/L and 1229 µmol/L, which was associated with an increased rate of apoptotic and dead cells. ZnO NP < 100 nm altered the cell cycle of LT97 cells but not that of Caco-2 cells. ZnO NP < 50 nm led to the formation of micronuclei in LT97 cells. The Ames test revealed no mutagenicity for both ZnO NP. Our results indicate the potential toxicity of ZnO NP after oral exposure, which should be considered before application.

Tridentate salphen‐type O,N,N′ chelators, upon acylation of the NH2 group, are capable of engaging an O,N,O′ coordination mode in addition to their inherent O,N,N′ donor character. In six‐coordinate silicon complexes of the type SiL2 [L = N‐(2‐carbamidophenyl)imine], these ligands were found to exclusively form SiN2O4 coordination spheres by engaging their tridentate O,N,O′ donor capability. Selected ligands L were also shown to preferably engage the O,N,O′ coordination mode when incorporated in five‐ and four‐coordinate silicon compounds of the type LSiPhX (X = Cl, F) and LSiPh2, respectively. The coordination modes of the herein presented six‐, five‐, and four‐coordinate silicon compounds represent the first examples of X‐ray structurally confirmed O‐silylated carbamides, which hence adopt structural features of C‐siloxyimines.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)