Structure of a novel nitrido technetium complex with the peptide chelate ligand KYCAR

A novel nitrido technetium complex was synthesized by the reaction of the KYCAR (lysyl-tyrosyl-cystyl-alanyl-arginine) ligand with [(n-C₄H₉)₄N][⁹⁹TcNCl₄]. The structure of the complex was analyzed by ¹H- and ¹³C-NMR and IR spectroscopy as well as by elemental analysis. The nitrido technetium complex with KYCAR has a square pyramidal structure in which two KYCARs coordinate to the Tc atom through both an N and a deprotonated S atom of cysteine. The complex possesses a trans configuration.     

Studies directed toward the total synthesis of pinnatoxin A: synthesis of the 6,5,6-dispiroketal (BCD ring) system by double hemiketal formation/hetero-Michael addition strategy

An efficient, highly stereoselective synthesis of the C10–C26 portion of pinnatoxin A has been achieved, wherein the key step is a highly stereoselective construction of the 6,5,6-dispiroketal (BCD ring) system by an intramolecular hetero-Michael addition of a hemiketal alkoxide reversibly formed under the influence of lithium methoxide.     

Determination of oxygen in gallium arsenide by3He activation analysis using substoichiometric precipitation

Distillation of fluoride as fluorosilicic acid and substoichiometric precipitation as lanthanum fluoride was studied for the determination of oxygen in gallium arsenide by³He activation analysis. Fluoride could be separated substoichiometrically with a good reproducibility by two distillations and successive precipitation with lanthanum. The oxygen concentration in gallium arsenide prepared by the horizontal Bridgman technique was 10 to 36 ppb and increased a little along the front, middle and tail portions in the crystal.     

Formation of nitridotechnetium (VI) μ-oxo dimer complexes with EDTA and EDDA

Reactions of [⁹⁹TcNCl₄]^– with ethylenediaminetetraacetic acid (EDTA) and ethylenediamine-N, N-diacetic acid (EDDA) in a mixture of water and acetone gave Tc^VIN-EDTA and Tc^VIN-EDDA complexes. The infrared spectra of both reaction products showed the existence of the TcN and C=O groups. The elemental analysis indicated the 11 TcN-ligand ratio in the EDTA and EDDA complexes. Electrophoresis showed that the Tc^VI-EDTA complex was an anionic species in a perchlorate solution. For the Tc^VIN-EDDA complex, neutral and anionic species were formed, depending on the pH of the solution. Formation of the -oxo dimer complexes was suggested from the UV-Vis absorption spectra.     

Automatic log P estimation based on combined additive modeling methods

Summary A program for the automatic estimation of the logarithm of the partition coefficient between 1-octanol and water phases (log P) has been developed as a component of a system entitled CHEMICALC (Combined Handling of Estimation Methods Intended for Completely Automated Log P Calculation). Log P values are calculated based on additive group contributions to log P. Three sets of groups are defined, and their contributions have been derived from the experimental log P values of 1465 molecules. The system divides a structural formula of a compound of interest into the groups whose increments are provided and then calculates its log P value. All processing after structure input is fully automated. This system has been tested for predicting the log P values of 1686 compounds. The accuracy is sufficient for many practical purposes.     

Calculation of nuclear magnetic shieldings using an analytically differentiated relativistic shielding formula

Two expressions for nuclear-magnetic-shielding tensor components based on analytically differentiating the electronic energy of a system are presented. The first is based on a second-order Douglas-Kroll-Hess approach, in which the off-diagonal block terms of the transformed Dirac Hamiltonian are diminished to second order with respect to both the electrostatic nuclear attraction potential V and the magnetic vector potential A. The second expression is based on the method of Barysz-Sadlej-Snijders, in which the off-diagonal block terms in the transformed Dirac Hamiltonian are completely eliminated with respect to purely V terms, while they are diminished to second order with respect to terms including A. The two approaches are applied to the calculation of nuclear magnetic shieldings of HX (X=F, Cl, Br, I), H2X (X=O, S, Se, Te), and noble gas X (X =He,Ne,Ar,Kr,Xe) systems with common gauge origins. The results show that relativistic corrections of higher than second order are negligibly small, except for the paramagnetic parts of I, Te, and Xe shieldings. The present calculations yield very large positive values for the anisotropy of proton shielding, deltasigma(H) = sigmaparallel(H)-sigmaperpendicular(H), of HI compared to previous reports. Unfortunately, no experimental values for the anisotropy of proton shielding in HI are available for verification.     

Carrier doping effect into quasi-one-dimensional bromo-bridged Ni(III) complexes with strong electron-correlation by Cu(II) ions, [Ni1-xCux(chxn)2Br]Br2-x

This communication will describe the electron doping effect into Ni(III) complexes by Cu(II) ions, [Ni(1-x)Cu(x)(chxn)(2)Br]Br(2-x) (x = 0.038 and 0.101) by using an electrochemical oxidation method. A drastic increase of electrical conductivity as well as a new absorption band around 0.5 eV in single crystal reflectance spectra was observed by doping Cu(II) ions, indicating the electron doping was successfully made. An ESR result shows unpaired electrons locate in the d(x2-y2) orbitals of Cu(II) and have almost no interaction with those of other ions.     

Facile deoxygenation of dicarbonyl compounds using a samarium diiodide-additive system

The reduction of alpha- and beta-dicarbonyl compounds was investigated with samarium diiodide in the presence of additive. Diketones and ketocarboxylic acids were easily reduced at room temperature to give the mono-alcohols in good to excellent yield, and ketoester afforded the saturated ester as the major product in moderate yield. These reductions containing the reductive deoxygenation can be rapidly performed under the facile and mild conditions by this method.     

Photocatalytic H2 evolution under visible-light irradiation over band-structure-controlled (CuIn)xZn2(1-x)S2 solid solutions

(CuIn)(x)Zn2(1-x)S2 solid solutions between a ZnS photocatalyst with a wide band gap and CuInS(2) with a narrow band gap showed photocatalytic activities for H(2) evolution from aqueous solutions containing sacrificial reagents SO(3)(2-) and S(2-) under visible-light irradiation (lambda >/= 420 nm). Pt (0.5 wt %)-loaded (CuIn)(0.09)Zn(1.82)S(2) with a 2.3-eV band gap showed the highest activity for H(2) evolution, and the apparent quantum yield at 420 nm amounted to 12.5%. H(2) evolved at a rate of 1.5 L h(-1) m(-2) under irradiation with a solar simulator (AM 1.5). Diffuse reflection and photoluminescence spectra of the solid solutions shifted monotonically to a long wavelength side, as the ratio of CuInS(2) to ZnS increased in the solid solutions. The photocatalytic H(2) evolution depended on the composition as well as the photophysical properties. DFT calculations suggested that the visible-light response should be derived from the contribution of Cu 3d and S 3p orbitals to the valence band and that of In 5s5p and Zn 4s4p orbitals to the conduction band, respectively. The contribution of these orbitals to the energy bands affected the photophysical and photocatalytic properties.