The geometries of the Ln complexes analyzed have been fixed to their experimental X-ray structures taken from the literature . We indicate the ligands with acac = acetylacetonate, dppz = dipyridophenazine, dpq = dipyridoquinoxaline, phen = 1,10-phenanthroline, hfac = hexafluoroacetylacetonate, glyme = dimethoxyethane, see Figure for the mark and colour code used in the paper.