Towards materials with planned properties: Dinuclear f-f helicates and d-f non-covalent podates based on benzimidazole-pyridine binding units

We have taken advantage of self-assembly processes associated with the induced fit concept to design multidentate segmental ligands based on substituted benzimidazole-pyridine moieties which lead to the selective formation of stable luminescent mononuclear lanthanide complexes, dinuclear f-f helicates and non-covalent d-f lanthanide podates. The influence of the various substituents on the stability and quantum yield of the non-covalent edifices is discussed. It is demonstrated that replacement of one benzimidazole moiety by a carboxamide group enhances considerably the luminescent properties of the supramolecular light-converting devices. Moreover, the introduction of a non-covalent d-block tripod (Zn-II, Fe-II) into the organic ligand increases the thermodynamic stability and the selectivity of the complexation process. The lanthanide podates containing a non-covalent Fe-II tripod display a spin crossover behavior in the temperature range 300-360 K leading to new materials with tunable magnetic properties. Finally, the multi-component self-assembly leading to the heterodinuclear noncovalent d-f podates is discussed together with the H-1 NMR characterization of intricate lanthanide complexes.