A Modular Approach to Inorganic Phosphazane Macrocycles

Inorganic macrocycles, based on non‐carbon backbones, present exciting synthetic challenges in the systematic assembly of inorganic molecules, as well as new avenues in host–guest and supramolecular chemistry. Here we demonstrate a new high‐yielding modular approach to a broad range of trimeric and hexameric S‐ and Se‐bridged inorganic macrocycles based on cyclophosphazane frameworks, using the building blocks [S=(H)P(μ‐NR)]₂. The method involves the in situ generation of the key intermediate [E (S )P(μ‐NR)]₂²⁻(E=S, Se) dianion, which can be reacted with electrophilic [ClP(μ‐NR)]₂ to give P^III/P^V hexameric rings or reacted with I₂ to give trimeric P^V variants. Important issues which are highlighted in this work are the competitive bridging ability of S versus Se in these systems and the synthesis of the first air‐stable and chiral inorganic macrocycles.     

Measurement of carnosine, homocarnosine and anserine by FASI capillary electrophoresis UV detection: applications on biological samples

A field amplified sample injection (FASI) capillary electrophoresis method with UV detection was developed for the separation and detection of carnosine-related peptides carnosine (Car), anserine (Ans) and homocarnosine (Hcar). The imidazole dipeptides were baseline-separated within 10 min by using 50 mmol/L Tris phosphate pH 2.2 as running buffer. The samples were diluted in water and directly injected on the capillary without complex cleanup and/or sample derivatization procedures. Using the electrokinetic injection, a sensitivity improvement of about 500-fold was achieved without any loss of separation efficiency if compared to the conventional sample injection. The detection limits for carnosine, anserine, and homocarnosine were between 0.4 and 0.5 nmol/L, thus improving of 10-100-fold the LOD of previous described methods based on laser induced fluorescence or chemiluminescence detection. This method has been applied to the analysis of homogenized rat tissue (heart, muscle and brain) and human cerebrospinal fluid (CSF).     

Constructing High‐Generation Sierpiński Triangles by Molecular Puzzling

Three generations of metalated trigonal supramolecular architectures, so‐called metallo‐triangles, were assembled from terpyridine (tpy) complexes. The first generation (G1) metallo‐triangles were directly obtained by reacting a bis(terpyridinyl) ligand with a 60° bite angle and Zn^II ions. The direct self‐assembly of G2 and G3 triangles by mixing organic ligands and Zn^II, however, only generated a mixture of G1 and G2, as well as a trace amount of insoluble polymer‐like precipitate. Therefore, a modular strategy based on the connectivity of ⟨tpy−Ru²⁺−tpy⟩ was employed to construct two metallo‐organic ligands for the assembly of G2 and G3 Sierpiński triangles. The metallo‐organic ligands L^A and L^B with multiple free terpyridines were obtained through Suzuki cross‐coupling of the Ru^II complexes, and then assembled with Zn^II or Cd^II to obtain high‐generation metallo‐triangular architectures in nearly quantitative yield. The G1–G3 architectures were characterized by NOESY and DOSY NMR spectroscopy, ESI‐MS, TWIM‐MS, and transmission electron microscopy.