A combined experimental and DFT study on the complexation of Mg2+ with beauvericin

From extraction experiments and γ-activity measurements, the extraction constant corresponding to the equilibrium Mg2+(aq) + 1·Sr2+(nb) ⇆ 1·Mg2+(nb) + Sr2+(aq) taking place in the two-phase water–nitrobenzene system (1 = beauvericin; aq = aqueous phase, nb = nitrobenzene phase) was evaluated as log Kex (Mg2+, 1·Sr2+) = 0.0 ± 0.1. Further, the stability constant of the 1·Mg2+ complex in nitrobenzene saturated with water was calculated for a temperature of 25 °C as log βnb (1·Mg2+) = 9.1 ± 0.2. By using quantum mechanical DFT calculations, the most probable structures of the non-hydrated 1·Mg2+ and hydrated 1·Mg2+·3H2O complex species were predicted.