Size-tunable micron-bubbles based on fluorous-fluorous interactions of perfluorinated dendritic polyglycerols.

This paper describes the behavior of various generations of polyglycerol dendrimers that contain a perfluorinated shell. The aggregation in organic solvents is based on supramolecular fluorous-fluorous interactions, which can be described by means of (19)F NMR spectroscopy. In order to study the interaction and aggregation phenomena of dendrimers with perfluorinated shell and perfluoro-tagged guest molecules we investigated [G3.

PhzA/B catalyzes the formation of the tricycle in phenazine biosynthesis.

Phenazines are redox-active bacterial secondary metabolites that participate in important biological processes such as the generation of toxic reactive oxygen species and the reduction of environmental iron. Their biosynthesis from chorismic acid depends on enzymes encoded by the phz operon, but many details of the pathway remain unclear. It previously was shown that phenazine biosynthesis involves the symmetrical head-to-tail double condensation of two identical amino-cyclohexenone molecules to a tricyclic phenazine precursor.

Mixed-metal (platinum, palladium), mixed-pyrimidine (uracil, cytosine) self-assembling metallacalix[n]arenes: dynamic combinatorial chemistry with nucleobases and metal species.

Reactions between the mononuclear mixed-nucleobase complex [Pt(en)(UH-N1)(CH2-N3)]+ (1; en: ethylenediamine; UH-N1: uracil monoanion bonded through the N1 atom; CH2-N3: neutral cytosine bonded through the N3 atom) and [Pd(II)(en)] or [Pd(II)(2,2'-bpy)] (2,2'-bpy: 2,2'-bipyridine) lead to libraries of compounds of different stoichiometries and different connectivities. In these compounds, the palladium entity binds to or cross-links either the N3 sites of uracil and/or the N1 sites of cytosine, following deprotonation of these positions to give uracil dianions (U) and cytosine monoanions (CH). Cyclic species, which can be considered as metallacalix[n]arenes, have been detected in several cases, with n being 4 and 8.

Pd2Ag triangle supported by two micro3-amidopyridine ligands.

[Pd(tmeda)(Hampy-N1)(H2O)]2+ (tmeda=N,N,N',N'-tetramethylethylenediamine; Hampy=2-aminopyridine) forms in the presence of Ag+ at pH 8-9 a triangular Pd2Ag complex containing two deprotonated ampy- ligands. It has been crystallized and structurally characterized with nitrate anions and a second co-crystallized AgNO3, [{Pd(ampy)(tmeda)}2Ag(micro-NO3)2Ag(NO3)2]. The two amidopyridine ligands are triply bridging, binding to Ag+ in a monodentate fashion viaN1, and to two PdII centres in a micro2-bridging fashion via the monodeprotonated N2 position.

Multiple metal binding to 6-oxopurine nucleobases as a source of deprotonation. The role of metal ions at N7 and N3.

Simultaneous metal coordination to N7 (Pt(II)) and N3 (Pd(II)) of N9-blocked guanine leads to a 10(4) fold acidification of the guanine-N(1)H position and hence to a virtual complete deprotonation of the N(1)H position at neutral pH. The chelate-tethered nucleobase ethylenediamine-N9-ethylguanine was employed and relevant acid-base equilibria were studied by pD dependent 1H NMR spectroscopy. CH2 resonances of the tether were assigned on the basis of NOESY and COSY experiments.