Lanthanide complexes article 6 chemical structure 6 gadolinium 6 2,2' bipyridine 4 2,2'-Dipyridyl 4 Acids 4 Aqua ligands 4 Asymmetric units 4 Atoms 4 Binding energy 4 Binding modes 4 Bipyridine 4 Butane 4 Chemical units 4 Crystal structures 4 Dihydrate 4 Dioic acids 4 Donor atoms 4 Gadolinium 4 Holmium 4 Hydrates 4 Itaconic acids 4 Ligands 4 Liquefied petroleum gas 4 Molecular Structure 4 Negative ions 4 Polymeric structures 4 Rotation 4 Rotation axis 4