3-(2-Bromo­benz­yl)-1-methyl-1H-imidazol-3-ium bromide

In the title compound, C11H12BrN2 +·Br−, the imidazole and phenyl rings are nearly perpendicular, making a dihedral angle of 87.71 (7)°. The crystal structure is stabilized by non-classical inter­molecular C—H⋯Br hydrogen bonds and inversion-related mol­ecules are linked through π–π inter­actions between the imidazole ring systems [centroid–centroid distance = 3.472 (6) Å]

Differential regulation of interleukin-6 expression in human fibroblasts by tumor necrosis factor-α and lymphotoxin

AbstractThe treatment of human diploid fibroblasts with tumor necrosis factor (TNP)-α and with lymphotoxin (LT) is associated with induction of interleuk-in-6 (IL-6) transcripts with TNF-α being 10-fold more potent than LT. Here we report on the TNF-α/LT-induced signaling mechanisms responsible for the regulation of IL-6 gene expression in these cells. Run-on assays demonstrated that both TNF-α and LT increase IL-6 mRNA levels by transcriptional activation of this gene. Stability studies of IL-6 transcripts in fibroblasts showed that TNF-α delayed IL-6 mRNA decay but not LT. The induction of IL-6 transcripts by TNF-α and LT was not inhibited by the isoquinoline sulfonamide derivative H7. Similarly, depletion of protein kinase C (PKC) by 12-O-tetradecanoyl-phorbol 13-acetate (TPA) did not change the ability of TNF-α and LT to induce IL-6 transcripts, demonstrating that stimulation by these agents may not be mediated by activation of PKC. Stimulation of IL-6 transcripts in fibroblasts did also not require new protein synthesis as exposure to the protein synthesis inhibitor cycloheximide (CHX) enhanced accumulation of IL-6 mRNA in the presence or absence of TNF-α or LT

Two-step solid-state synthesis of PEPPSI-type compounds

peer-reviewedThe two-step mechanochemical preparation of carbene–pyridine complexes of palladium and platinum is reported. The organometallic products, which represent a class of commercially available catalysts, are rapidly formed in excellent yield proving solvent-free synthesis to be a viable synthetic alternative even in the case of NHC-containing compounds

Palladium complexes of o-xylyl-linked alkoxybenzimidazolin-2-ylidenes: interesting structural conformations and application as pre-catalysts

New PdBr2-bis(N-heterocyclic carbene) complexes derived from 4,7-dibutoxybenzimidazole and 5,6-dibutoxybenzimidazole have been synthesized and structurally and spectroscopically characterized.The complexes show much greater solubility compared to the parent complex derived from benzimidazole, and interesting structural characteristics dependent on the position of the butoxy substituents. The complexes display high activities in the coupling of aryl iodides in the Mizoroki-Heckreaction and moderate activities in the Suzuki-Miyaura coupling of inactivated aryl bromides at low catalyst loadings, although activity differences between pre-catalysts has been observed. Structuralstudies suggest electronic effects within the complexes to be strongly affected by steric interactions between the hydrogen atoms of the o-xylyl bridges and the benzimidazole components and their substituents

Estimating π binding energy of N-Heterocyclic carbenes: The role of polarization

International audienceIn this work, the tuneability of the π acceptor or donor properties of a set of N-heterocyclic carbenes (NHCs) with a wide spectrum of electronic characteristics is established by means of density functional theory and energy decomposition analysis (EDA) tools. Even though the main orbital interaction contribution to the NHC coordination is the σ donation, a significant contribution of the π interactions to the bond is observed. By means of carefully selected coordination sites, different contributions to the π interactions could be identified and isolated. It includes not only the well known back donation and donation interactions, but also the intrafragment polarization, which has not been considered in previous studies. This can be obtained through the use of the extended transition state method for EDA combined with the natural orbitals for chemical valence and the constrained space orbital variation analysis. The contributions vary with the position of the heteroatoms and the presence of exocyclic substituents; the donation/backdonation π interactions between NHC and the coordination site can range between 2 and 61% of the total π orbital interactions, while the rest is owed to intrafragment polarization. Our results do not only contribute to the understanding of the electronic structure of NHC-based complexes, giving ways to improve their catalytic properties, but also provide comprehension on the modelization methods used to study their donor–acceptor interactions