A method for the calculation of maximum and minimum band boundaries of feasible solutions corresponding to the species profiles estimated by multivariate curve resolution is presented. The method is based on a non-linear constrained optimization of an objective function defined by the ratio of the signal contribution of a particular species to the whole measured signal. Implementation of constraints such as normalization, closure, non-negativity, unimodality and local rank/selectivity during the non-linear optimization and their effect on the calculation of the feasible solutions are studied in detail. Calculation of the band boundaries is shown for different simulated and real two-way data examples of increasing complexity. Copyright © 2001 John Wiley & Sons, Ltd.

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Calculation of maximum and minimum band boundaries of feasible solutions for species profiles obtained by multivariate curve resolution

Ion-exchange fractionation of copper and zinc isotopes

The introduction of a trifluoromethyl (CF3) group can dramatically improve a compound’s biological properties. Despite the well-established importance of trifluoromethylated compounds, general methods for the trifluoromethylation of alkyl C–H bonds remain elusive. Here we report the development of a dual-catalytic C(sp3)–H trifluoromethylation through the merger of light-driven, decatungstate-catalysed hydrogen atom transfer and copper catalysis. This metallaphotoredox methodology enables the direct conversion of both strong aliphatic and benzylic C–H bonds into the corresponding C(sp3)–CF3 products in a single step using a bench-stable, commercially available trifluoromethylation reagent. The reaction requires only a single equivalent of substrate and proceeds with excellent selectivity for positions distal to unprotected amines. To demonstrate the utility of this new methodology for late-stage functionalization, we have directly derivatized a broad range of approved drugs and natural products to generate valuable trifluoromethylated analogues. Preliminary mechanistic experiments reveal that a ‘Cu–CF3’ species is formed during this process and the critical C(sp3)–CF3 bond-forming step involves the copper catalyst. Despite the importance of trifluoromethylated compounds, direct catalytic methods for the conversion of C(sp3)–H bonds into the corresponding C(sp3)–CF3 analogues have remained elusive. This transformation has now been achieved by the merger of copper catalysis with decatungstate photocatalysis, enabling the C(sp3)–H trifluoromethylation of abundant feedstocks, natural products and pharmaceuticals.

The merger of decatungstate and copper catalysis to enable aliphatic C(sp 3)–H trifluoromethylation

Squaramide-Based Reagent for Selective Chromogenic Sensing of Cu(II) through a Zwitterion Radical

The local environment of the Cu2+ ion in copper chloride solutions has been investigated by x-ray absorption spectroscopy. Three aqueous solutions of CuCl2 with increasing Cl−/Cu2+ ratio have been examined. An advanced data analysis including multiple-scattering effects produced quantitative information on the chlorocuprate complexes present in solution and provided evidence for an increasing degree of complex formation between Cu2+and Cl− ions with increasing chloride concentration. The presence of Cu–Cl interactions at the axial site has been detected in a 0.1 M CuCl2 solution for the first time. At higher chloride concentrations (Cl−/Cu2+ratios equal 10 and 30) the equatorial positions in the distorted octahedral copper coordination are occupied by 3.2 and 3.0 oxygens and 0.8 and 1.0 chloride ions, respectively, while the axial positions are occupied by 1.2 and 1.0 oxygens and 0.8 and 1.0 chloride ions, respectively. The results are found to be consistent with previous x-ray and neutron diffraction stu...

Structural investigation of copper(II) chloride solutions using x-ray absorption spectroscopy

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M. J. Schwing-Weill

Papers

Stability and electronic spectra of the copper(II) chloro complexes in aqueous solutions