An insight into interaction of Fe2+ with glycylglycine: A DFT study

This study performed at B3PW91/6-311++G(d,p)(LANL2DZ+f for Fe) level shows that the glycylglycine-Fe2+(3d6) complexes in 1I, 3H and 5D states behave rather similarly. The ground states are all predicted to be quintet complexes. In the ground state, the most stable complex adopts a structure in which the metal is tridentate and coordinated by two oxygen atoms and the N terminus nitrogen atom. Interestingly, the most stable conformation of triplet states is in zwitterionic form. The charge transfer of Fe2+ to glycylglycine in quintet states is less than that of single states and triplet states. The charge transfer plays an important role in the binding process of Fe2+ with glycylglycine. The main effect of the electrostatic interaction with a continuum having the dielectric constant of water is a variation of the energy differences between these conformations.