Alkaloids ofDelphinium grandiflorum

Chemistry of Natural Compounds -     

Solvent effects on the redox properties of Cu complexes used as mediators in atom transfer radical polymerization

Solvent effects on the redox properties of six Cu(I) complexes used as mediators in atom transfer radical polymerization (ATRP) have been studied using cyclic voltammetry. The six ligands used were tris[2-(dimethylamino)ethyl]amine, N-(n-propyl)-2-pyridylmethanimine, N,N,N',N',N'-pentamethyldiethylenetriamine, 1,1,4,7,10,10-hexamethyl-triethylenetetramine, 2,2'-bipyridine, and 1,4,8,11-tetraaza-1,4,8,11-tetramethylcyclotetradecan. The solvents used were DMSO, DMF, MeCN, MeOH, IP, and BuOH. Significant solvent effects were observed and quantitatively analyzed in terms of Kamlet-Taft relationships. The resulting Kamlet-Taft equations were found to successfully describe the solvent effects and could thus be used as tools for the design of ATRP in new solvents. The solvent sensitivity of the different ligands and the nature of the solvent effects are also discussed to some extent.     

Reversible bond formation in a gold-atom-organic-molecule complex as a molecular switch

We report on the formation of a metal-molecule complex that can be used as a molecular switch. Using a cryogenic scanning tunneling microscope, a covalent bond was formed reversibly between a gold atom and a perylene-3,4,9,10-tetracarboxylic dianhydride molecule supported by a thin insulating film. The bonded and the nonbonded state of the complex were found to be associated with different charge states, and the switching between the two states was accompanied by a considerable change in the tunneling current. Atomic force microscopy molecular imaging was employed to determine precisely the atomic structure of the complex, and the experimental results were corroborated by density functional theory calculations.     

ChemInform Abstract: Nickel Vanadium Tellurium Oxide,NiV2Te2O10.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.     

A thermally stable Pt/Y-based metal-organic framework: Exploring the accessibility of the metal centers with spectroscopic methods using H2O, CH3OH, and CH3CN as probes

A metal-organic framework (MOF) based on Pt, Y, and 2,2'-bipyridine-5,5'-dicarboxylate (BPDC), stable up to 400 degrees C, has been synthesized and characterized. In this MOF, the Pt centers are coordinated to Cl and the N atoms of the BPDC unit, giving a local environment similar to that found in a series of Pt-organic complexes with catalytic activity toward C-H bond cleavage of alkanes. This new material is a heterogeneous counterpart to the corresponding metal-organic complex. The structure, determined by single-crystal XRD data, is the repetition of three covalently bonded layers. These layers form a block, which is stacking as an (a)(b)(c) sequence along the crystallographic b-axis. Each layer contains the Pt-organic unit, while Y atoms represent the connection between adjacent layers. No covalent connection is present between layer (a) of a block and layer (c) of an adjacent block. EXAFS (BM29 at the ESRF) analysis supports the XRD data. As this MOF crystallizes under hydrothermal conditions, water acts both as solvent and as a direct ligand of Y. Accessibility to the metal centers is demonstrated by reversible water desorption/readsorption, as determined by TPA/TPD, FTIR, UV-vis, EXAFS, and XANES. Importantly, the results show that the as-synthesized material will not suffer a permanent loss in porosity upon solvent removal. In addition to water, methanol, ethanol, and acetonitrile can also access the internal void of the dehydrated phase.     

Megavariate Analysis of Environmental QSAR Data. Part II – Investigating Very Complex Problem Formulations Using Hierarchical, Non-Linear and Batch-Wise Extensions of PCA and PLS

Summary Three extensions of the basic PCA and PLS methodologies are described. These extensions are hierarchical, non-linear and batch-based in nature. The objectives of these methods are to assist in problem understanding and problem solving in very complex (QSAR) problem formulations. The method extensions are illustrated using two example QSAR data sets containing many X- and Y-variables.