The use of predisposed segmental ligands in multi-component self-assembly processes allows the preparation of triple-helical heterodimetallic d–f complexes in which each pair of metal ions is isolated and protected from external interactions. The selection of the programmed heterodimetallic edifice within the dynamic virtual library arising from the mixture of the reacting components relies on a judicious matching between the stereochemical preferences of the metal ions and the binding abilities of the receptors combined with a reliable characterisation of the thermodynamic equilibria controlling the assembly process. Minor modifications of the receptors (donor groups, peripheral substituents) have considerable effects on formation of heterodimetallic d–f complexes (HHH)-[LnM(L)3] {L = bis[1-methyl-2-(2-pyridyl)benzimidazol-5-yl]methane derivative} thus leading to successive improvements of the stability in aqueous solvent and to the fine tuning of structural and electronic properties. The implementation of specific light-converting properties, thermochromism, switchable magnetism and tunable dynamic behaviour are discussed together with the development of new paramagnetic NMR techniques for characterising lanthanide-containing dimetallic architectures in solution.