Aryl bromides of the type BrCeHz(CHzNMez)z-2,6-R-4 (R = NHz, MeO, H, C1, MeC(0)) have been synthesized and have been used to prepare the corresponding organonickel(I1) complexes [NitCsHz(CHzNMez)z-2,6-R-4)Brl by an oxidative addition reaction to Nio(COD)2 (COD = cycloocta-1,5-diene). The effect that the para substituent of the monoanionic, N,C,N' terdentate, aryl ligand has on the electronic properties of the nickel complexes has been investigated by 13C NMR and UV/vis spectroscopy as well as by electrochemistry. The results show that para substitution on the aryl ligand markedly influences the nickel(I1) center; electron-donating substituents increase the ease of oxidation to NiIII, and direct correlations exist between chemical shift data for the carbon atom bonded to nickel and appropriate Hammett parameters.

The reactivity of metal cluster compounds toward H2 and the structures and properties of hydride-containing cluster compounds are important because they should provide a better understanding of homogeneous and heterogeneous catalytic processes.1 Hydrido compounds of heterometallic clusters that contain gold have been described, and the presence of hydride bridges between gold and the helero metal is well documented.2-6 In [Ru(dppm)2(#t-H)2(AuPPh3)2]+

The lipopeptide tripalmitoyl-S-glycerylcysteine (Pam3Cys) is derived from the N-terminal part of bacterial lipopeptides and is a polyclonal B-lymphocyte and macrophage activator. Derivatives of Pam3Cys constitute highly potent, nontoxic immunoadjuvants, and lipopeptide−antigen conjugates have found important applications as novel fully synthetic low-molecular-weight vaccines. To establish a possible correlation between molecular structure, aggregation properties, and biological activities, we have studied the self-assembly and monolayer properties of a range of Pam3Cys derivatives using transmission electron microscopy (TEM) and a Langmuir-film balance combined with a Brewster angle microscopy (BAM). It was found that the chirality of the glyceryl moiety and the additional serine unit impacted on the mode of aggregation and the monolayer properties. Correlations are discussed between these physicochemical properties and biological activities.

A novel class of glycopeptidolipids is described, which potentially can be used as a novel antigen-delivery system. The compounds have been prepared by a combination of solid-supported and solution-based methods. The use of the orthogonally protected FmocLysDde derivative provided an opportunity to incorporate two different types lipids. It was found that the model compound 1 forms aggregates in aqueous media which can be described as rod or tubelike structures. The aggregates can be stabilized by topotactic photopolymerization. Studies on the structural analogues 2-5 revealed the effect of the carbohydrate, peptide, and lipid moiety on the aggregation properties. It is concluded that none of the structure elements can lay claim to be exclusively important for the formation of highly organized aggregates such as tubes, fibers, or helical ribbons from 1, but the presence of all of these structural elements afforded the most uniformly shaped extended structures.