Fr Francium

The use of microwave heating for the synthesis of (N-heterocyclic carbene)-bearing complexes of Cu, Ag and Au allows for a drastic reduction of the reaction times required by conventional heating, while affording comparable or better yields of the desired complexes.

The use of microwave heating for the direct synthesis of (NHC)MCl complexes (NHC = N-heterocyclic carbene; M = Cu, Ag, Au) in very short reaction times is presented. Comparable or better yields than those reported by using conventional heating can be obtained with this protocol.

To identify the chemical species involved in a unique, vanadium-based chemical oscillator reaction, products derived from indole in the oscillation solution were isolated and characterized. NMR and mass spectra showed that 3,3-dichloro-2-oxoindole and isatin were formed during the oscillation process. The formation of these two compounds suggests that peroxo species such as CHCl₂OO^· and CHCl₂OOH play a key role in the construction of the oscillation system. A skeletal model for the system is proposed based on these findings.

Products derived from indole in a vanadium-based oscillation solution were identified to be 3,3-dichloro-2-oxoindole and isatin. Peroxo species such as CHCl₂OO^· and CHCl₂OOH were found to play a key role in the construction of the chemical oscillation system. A skeletal model for the oscillation reaction is proposed.

A novel method to prepare TiO₂-coated Ag nanowire arrays for use as multifunctional surface enhanced Raman scattering (SERS) active substrates is introduced. Such an array is made by the synthesis of an Ag nanowire array utilizing an anodic aluminum oxide (AAO) template, followed by coating of the Ag wires with a layer of titania that is several nanometers thick. Employing these TiO₂-coated Ag nanowire substrates in the detection of organic contaminants allows high SERS enhancement to be achieved. Moreover, owing to the high photocatalytic activity of titania, the substrate can degrade target molecules into small inorganic molecules under UV irradiation, and in this manner the arrays are able to self-clean. The unique properties of this integrated substrate enable it to exhibit its feasibility as an analytical tool for the assessment of environmental pollution and thus to assist in the detection and disposal of contaminants.

A novel method to prepare TiO₂-coated Ag nanowire arrays for use as multifunctional surface-enhanced Raman scattering (SERS) active substrates is introduced. Employing this substrate for the detection of organic contaminants can lead to high SERS enhancement. Owing to the high photocatalytic activity of TiO₂, the substrate can degrade target molecules into small inorganic molecules, and in this way the arrays are able to self-clean.

Redox and coordination processes are coupled in the course of reactions of the organic electron donors 1,2,4,5-tetrakis(tetramethylguanidino)benzene (1) and 1,2,4,5-tetrakis(N,N′-dimethyl-N,N′-ethyleneguanidino)benzene (2) with silver salts. Experiments with several different silver salts show that the product structure is significantly affected by the properties of the anion in these salts. Chain polymers are the products of reactions with AgPF₆ or AgBF₄, in which dicationic organic building blocks are connected by silver ions. Experiments with AgNO₃ yielded either dinuclear complexes (with 1) or 2D networks (with 2). If the salt Ag[Al{OC(CF₃)₃}₄], featuring a weakly coordinating anion, was used, simple silver-free salts of the guanidine dication were obtained. The thermal stability, optical properties, and electrical conductivity were studied in detail for the product polymer {[(1)Ag](PF₆)₃}_n. From the temperature dependence of the electric conductivity, this compound was found to be a semiconductor with a band gap of approximately 3 eV. The experiments were complemented by quantum chemical calculations at density-functional-theory level on the band structure of this and a related polymer. The electronic situation was further analyzed with the aid of molecular model complexes, which were either synthesized or calculated.

1D coordination polymers of oxidized guanidino-functionalized aromatic ligands were prepared by coupled oxidation and coordination with silver salts. The structures and electronic properties of these semiconducting materials were analyzed.

Two new hybrid ligands that exhibit organic as well as siloxane chains between four phosphorus atoms in bridge-head positions were synthesized. These species show a very different ability with regard to the formation of coordination compounds. Whereas compound 1 with the short (C₂H₄)₂O ether units shows no ability to act as a ligand, the compound with the longer (C₂H₄O)₂C₂H₄ chains between the siloxane fragments could be obtained as the free ligand and with incorporated Li₂I₂ and Ag₂I₂ units. The observed coordination modi of the lithium and silver ions in these complexes corresponds to the HSAB- or Pearson concept. The silver ions prefer the soft phosphorus atoms as a bonding partner, while, for lithium, coordination by the hard oxygen atoms is favoured.

Empty and filled hybrid cage compounds with siloxane as well as ether units between four phosphorus bridge-head atoms were obtained from the deprotonation of the cyclic siloxadiphosphane [O(SiiPr₂)₂PH]₂ and subsequent reaction with diiodo ethers. These compounds show very different coordination behaviour depending on the length of the ether chain and the metal cation used.

The cover picture shows a ball-and-stick model of the larger cage of the vanadium-based metal–organic framework (MOF) having the MIL-101 topology (MIL: Materials of the Institute Lavoisier; V: yellowish green octahedra, C: yellow, O: red). Similar to its chromium analogue, the structure is built up of trimeric [Va ball-and-stick model of the larger cage of the vanadium-based metal?organic framework (MOF) having the MIL-101 topology (MIL: Materials of the Institute Lavoisier; V: yellowish green octahedra, C: yellow, O: red). Similar to its chromium analogue, the structure is built up of trimeric [V₃(μ₃-O)Cl(DMF)₂]⁶⁺ (DMF: N,N′-dimethylformamide) units that are interconnected by 1,4-benzenedicarboxylate (BDC^2–) linkers to form supertetrahedra (ST). The ST are further connected to each other to obtain the augmented zeolite Mobil Thirty-Nine (MTN) type of framework, which consists of smaller and larger mesoporous cages having diameters of 29 and 34 Å, respectively. The redox-active MOF material exhibits a high uptake of nitrogen and of carbon dioxide. Details are discussed in the article by P. Van Der Voort et al. on p. 2481 ff.

The FK506 binding protein 51 (FKBP51) is best known as an Hsp90-associated co-chaperone that regulates the responsiveness of steroid hormone receptors. In human genetic association studies, FKBP51 has repeatedly been associated with emotion processing and numerous stress-related affective disorders. It has also been implicated in contributing to the glucocorticoid hyposensitivity observed in New World primates. More recently, several research groups have consistently shown a protective effect of FKBP51 knockout or knockdown on stress endocrinology and stress-coping behavior in animal models of depression and anxiety. The principal druggability of FKBP51 is exemplified by the prototypic FKBP ligands FK506 and rapamycin. Moreover, FKBP51 is highly suited for X-ray co-crystallography, which should facilitate the rational drug design of improved FKBP51 ligands. In summary, FKBP51 has emerged as a promising new drug target for stress-related disorders that should be amenable to drug discovery.

Low-stress target: The FK506 binding protein 51 regulates responsiveness to stress hormones in animals and humans. Herein we summarize the status of FKBP51 as a newly emerged drug target for psychiatric disorders and possibly for endocrine cancers.

To identify novel c-Met inhibitors, sequences and crystal structures of the human kinome were analyzed to find interesting hinge binders that have been underexplored within the tyrosine kinase subfamily. Through this study, the imidazolopyridine ring was selected as a novel c-Met hinge-binding inhibitor scaffold. A series of derivatives was prepared, and the structure–activity relationships were studied. Among these, one compound in particular showed excellent activities in enzymatic and cellular assays, good in vitro metabolic stability, and favorable pharmacokinetic parameters. When administered orally, the compound inhibited tumor growth in an NIH-3T3/TPR-Met xenograft model and did not show adverse effects on body weight. The present work not only conceptually demonstrates a new route for designing novel kinase inhibitors by using known structural information of ligand–hinge interactions but also provides a series of imidazolopyridine derivatives as potent c-Met inhibitors.

Amazing imidazolopyridines: By screening crystal structures of members of the human kinome and analyzing hinge binders, we designed a novel scaffold for inhibitors of c-Met. A series of derivatives were prepared and their SARs were studied; among them, compound 41 showed good in vitro and in vivo activities and proved to be a promising lead compound for further investigation.