Subcomponent self-assembly of circular helical Dy$_{6}$(L)$_{6}$ and bipyramid Dy$_{12}$(L)$_{8}$ architectures directed via second-order template effects

In situ metal-templated (hydrazone) condensation also called subcomponent self-assembly of 4,6-dihydrazino-pyrimidine, o-vanillin and dysprosium ions resulted in the formation of discrete hexa- or dodecanuclear metallosupramolecular Dy$_{6}$(L)$_{6}$ or Dy$_{12}$(L)$_{8}$ aggregates resulting from second-order template effects of the base and the lanthanide counterions used in these processes. XRD analysis revealed unique circular helical or tetragonal bipyramid architectures in which the bis(hydrazone) ligand L adopts different conformations and shows remarkable differences in its mode of metal coordination. While a molecule of trimethylamine acts as a secondary template that fills the void of the Dy$_{6}$(L)$_{6}$ assembly, sodium ions take on this role for the formation of heterobimetallic Dy$_{12}$(L)$_{8}$ by occupying vacant coordination sites, thus demonstrating that these processes can be steered in different directions upon subtle changes of reaction conditions. Furthermore, Dy$_{6}$(L)$_{6}$ shows an interesting spin-relaxation energy barrier of 435 K, which is amongst the largest values within multinuclear lanthanide single-molecular magnets.