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522 research data, page 1 of 53

An Adamantane-Based Coordination Framework with the First Observation of Discrete Metal Sulfonate Clusters

By employing a rigid adamantane-based unit as a spacer, a coordination solid with an open channel layered structure results showing the first observation of metal sulfonate clusters. The design approach employed enforces a structural mismatch of metal and ligand coordinative preferences.

Comparative Kinetic Studies of the Copolymerization of Cyclohexene Oxide and Propylene Oxide with Carbon Dioxide in the Presence of Chromium Salen Derivatives. In Situ FTIR Measurements of Copolymer vs Cyclic Carbonate Production

The catalysis of the reaction of carbon dioxide with epoxides (cyclohexene oxide or propylene oxide) using the (salen)CrIIICl complex as catalyst, where H2salen = N,N‘-bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexenediimine (1), to provide copolymer and cyclic carbonate has been investigated by in situ infrared spectroscopy. As previously demonstrated for the cyclohexene oxide/CO2 reaction in the presence of complex 1, coupling of propylene oxide and carbon dioxide was found to occ...

Melt Morphology of Polystyrene−Poly(ethylene oxide) Metallo-Supramolecular Diblock Copolymer

Melt Morphology of Polystyrene−Poly(ethylene oxide) Metallo-Supramolecular Diblock Copolymer

Conversion of Homocysteine to Methionine by Methionine Synthase: A Density Functional Study

Jensen, Kasper P.; Ryde, Ulf (2003)
Publisher: Figshare
This communication reports a theoretical study of the conversion of homocysteine to methionine by methionine synthase. The reaction pathway is based on density functional calculations with large basis sets, including thermodynamic, relativistic, and solvent effects. We find that the suggested SN2 mechanism explains well the experimentally observed reaction rate. The results show that the reaction is highly polar, as reflected in the change of charge density along the reaction coordinate. It i...

Dependence of Optical Transition Energies on Structure for Single-Walled Carbon Nanotubes in Aqueous Suspension:  An Empirical Kataura Plot

Weisman, R. Bruce; Bachilo, Sergei M. (2003)
Publisher: Figshare
Spectrofluorimetric data for identified single-walled carbon nanotubes in aqueous SDS suspension have been accurately fit to empirical expressions. These are used to obtain the first model-independent prediction of first and second van Hove optical transitions as a function of structure for a wide range of semiconducting nanotubes. To allow for convenient use in support of spectral studies, the results are presented in equation, graphical, and tabular forms. These empirical findings ...

Potent Small-Molecule Binding to a Dynamic Hot Spot on IL-2

The complexes between IL-2 and two similar small molecules, one a lead compound and the other a potent, affinity-optimized compound, were determined by X-ray crystallography. The lead compound (IC50 = 6 μM) bound to a hot spot on IL-2 in a groove that is not apparent in either the unliganded protein or a complex between IL-2 and a weakly bound drug fragment. The affinity-optimized compound (IC50 = 0.06 μM), which has an added aromatic acid fragment, bound in the same groove as the lead compou...

NN Bond Cleavage by a Low-Coordinate Iron(II) Hydride Complex

Reaction of the three-coordinate complex LFeCl (L = bulky β-diketiminate) with KBEt3H gives a dark red iron(II) hydride complex. The complex is a dimer in the solid state, but spectroscopy and kinetics suggest that an orange three-coordinate monomer is in equilibrium with the dimer in solution. The double bond of azobenzene is completely cleaved by heating with the hydride complex, and a hydrazido intermediate can be isolated.

Highly Diastereoselective Synthesis of C(6)-Functionalized Dihydroimidazotriazines

The first examples of C(6)-substituted 7-hydroxy-6,7-dihydro-5H-imidazo[1,2-b][1,2,4]triazines have been prepared by ring closure of different 5(2H)-1,2,4-triazin-3-ones 1a−c with 40% aqueous glyoxal and various nucleophiles (alcohols, thiols, or amines). The structure and exact stereochemistry of 2a was established by a single X-ray diffraction study and 1H and 13C NMR spectra analysis. The process was shown to be totally regio- and diastereoselective. A mechanism involving an imine...

Self-Assembled Nanotubes that Reversibly Bind Acetic Acid Guests

A large bis-urea macrocycle was synthesized and assembled into columnar nanotubes containing a sizable cavity. This purely organic nanotube is held together primarily by hydrogen bonding and yet shows remarkable thermal stability up to 180 °C in the presence and absence of acetic acid guest. This enables the nanotube to be used as reusable organic zeolite.