New dinuclear cobalt(II) and zinc(II) complexes of a carboxylate-rich dinucleating ligand: Synthesis, structure, spectroscopic characterization, and their interactions with sugars

摘要

Sugar-metal ion interactions in aqueous medium are involved in many biochemical processes such as the transport and storage of metals, the function and regulation of sugar-metabolizing metalloenzymes, the mechanism of action of metal-containing pharmaceuticals, and toxic metal metabolism. To understand such interactions we synthesized and fully characterized two new dinuclear cobalt(II) and zinc(II) complexes as carbohydrate binding models for xylose/glucose isomerases (XGI). Synthesis of the dicobalt complex, Na _3[Co _2(ccdp)(μ-HCO _2)]BF _4· 9H _2O·2CH _3OH (1), was performed in methanol with stoichiometric amounts of Co(BF _4) _2·6H _2O and the dinucleating ligand, H _5ccdp (H _5ccdp = N,N'-bis[2-carboxybenzomethyl]-N,N'-bis[carboxymethyl]-1,3-diaminopropan-2-ol), in the presence of NaOH at ambient temperature in an argon glovebox. Similarly, the dizinc complex, [NMe _4] _2[Zn _2(ccdp)(μ-OAc) ]·CH _3OH (2), was synthesized from Zn(OAc) _2· 2H _2O and H _5ccdp in the presence of NMe _4OH at ambient temperature in methanol. Binding of the complexes with carbohydrates was investigated under different reaction conditions. In aqueous alkaline media, complexes 1 and 2 showed chelating ability towards the biologically important sugars, d-glucose and d-xylose, and a polyalcohol enzyme inhibitor (xylitol). In solution, each complex forms a 1:1 complex-substrate bound product with specific binding constant values. Synthesis, characterization details, and substrate binding using spectroscopic techniques and single-crystal X-ray diffraction are reported.