Study of potential binding of biologically important sugars with a dinuclear cobalt(II) complex

The investigation of the sugar-metal ion interactions remains one of the main objectives of carbohydrate coordination chemistry because the interactions between metal ions and carbohydrates are involved in many biochemical processes. The potential binding interaction between a five-coordinate dinuclear cobalt(II) complex, Na2[Co2(tcdc)(μ-OAc)] (1) [Na5tcdc = Sodium-N,N,N′,N′-tetrakis(sodium carboxylate methyl)-2,6-diaminocresolate] and biologically important sugar substrates (d-glucose, d-xylose, and d-mannose) has been studied. In alkaline media, the complex 1 shows an excellent chelating ability toward these sugar substrates. A combined approach of FTIR and UV-vis spectroscopic investigations shows that the complex forms a 1:1 complex/substrate-bound product. UV-vis spectra indicate a significant blue-shift of the absorption maximum of metal complex during carbohydrate coordination highlighting the sugar binding ability of complex 1. The apparent binding constants of the substrate-bound cobalt(II) complexes have been determined from the UV-vis titration experiments.