Predicted structure and selectivity of 3d transition metal complexes with glutamic N , N -bis(carboxymethyl) acid

The complexation of transition metals with a rather new aminopolycarboxilic ligand, the glutamic N, N-bis(carboxymethyl) acid (GLDA) is investigated using the density functional at the PBE/TPZ level of theory. In order to predict the selectivity of metals and to gain insight into factors influencing the calculated log K values, the GLDA ligand is studied in the gas phase and in solvent with the electrostatic COSMO model. In the absence of crystallographic data, most complexes prefer a pentacoordinated structure in gas phase. On the contrary, in presence of solvent the two structures can coexist, copper excepted, which does not adopt the octahedral form. Good correlations are found between the experimental thermodynamic values and several calculated parameters such as charge transfer, bond descriptors, or bonding free energy energies. The obtained calculations show that, copper excepted, the complexes are octahedral and for a selective separation of cations, the copper cation will be the first to be efficiently complexed.