Stereoselective sulfoxidation catalyzed by achiral Schiff base complexes in the presence of serum albumin in aqueous media
摘要:
Four coordination complexes ML derived from an achiral Schiff base ligand (H2L = 2,2'-[(1,2-ethanediyl) bis(nitrilopropylidyne)]bisphenol) have been synthesized and characterized. A method is described for the enantioselective oxidation of a series of aryl alkyl sulfides using the coordination complexes in the presence of serum albumins (SAs) in an aqueous medium at ambient temperature. The mixture of metal complexes with serum albumins is useful for inducing asymmetric catalysis. The complex, albumin source and substrate influence stereoselective sulfoxidation. At optimal pH with the appropriate oxidant, some of ML/SA systems are identified as very efficient catalysts, giving the corresponding sulfoxides in excellent chemical yield (up to 100%) and good enantioselectivity (up to 94% ee) in certain cases. UV-visible spectroscopic data provide evidence that stronger binding between the complex and serum albumin lead to higher enantioselectivity. (C) 2017 Elsevier Ltd. All rights reserved.
Synthesis and structural and magnetic characterization of discrete phenolato and imidazolate bridged Gd(III)–M(II) [M=Cu, Ni] dinuclear complexes
作者:Cynthia Brewer、Greg Brewer、W.Robert Scheidt、Maoyu Shang、Everett E. Carpenter
DOI:10.1016/s0020-1693(00)00354-6
日期:2001.2
Three dinuclear complexes formed by the reaction of Gd(hfa)(3) (hfa is hexafluoroacetylacetonate) with Schiff base complexes of Cu(II) and Ni(II) have been synthesized and characterized. The crystal structures of the complexes [Gd(hfa)(3)M(prpen)] M = Cu(II (1)), Ni(II) (2)} are reported. (H(2)prpen is the Schiff base derived from the condensation of 2 equiv. of 2-hydroxypropiophenone and 1 equiv. of ethylenediamine.) Both 1 and 2 are discrete dinuclear complexes consisting of an eight coordinate Cd atom which is bridged to four coordinate M(II) via both phenolate oxygen atoms of the prpen ligand. The crystal structure shows there is no tendency toward dimerization between adjacent Cu(II) Schiff base units in 1. Cryomagnetic measurements show a ferromagnetic interaction between Gd(III) and Cu(II) in 1 as predicted by theory with J = 1.91 cm (- 1). The reaction of Gd(hfa), with Ni(L) (H2L is the Schiff base derived from the condensation of 1 equiv. each of 5-chlorobenzophenone, 1,2-diaminobenzene, and 5-methyl-4-imidazolecarboxaldehyde) produced Gd(hfa),Ni(L) (3) in which imidazolate is available to bridge Gd(III) and Ni(II). (C) 2001 Elsevier Science B.V. All rights reserved.
Synthesis, Characterization and Electrochemical Behaviour of Some Manganese and Copper Complexes with Tetradentate Schiff Base Ligands