The ground states and binding energies of Eu3+-L (L = H2O, H2S, NH2CH3, S(CH3)(2), imidazole) complexes has been determined using ab initio techniques. The binding is mostly electrostatic as expected. The empty f orbital is different for the S compounds, being a pi-like orbital, while for the O and N containing ligands it is a sigma-like orbital. However, the range in the binding energies for the different f holes is small. (C) 2002 Elsevier Science B.V. All rights reserved.