Functional (Supra)Molecular Nanostructures - ruben-group

Habilitation Dr. Mario Ruben
ULP Strasbourg
Transition metal coordination complexes of a [2x2] grid-type architecture comprise two-
dimensional arrays of metal ions connecting a set of organic ligands to generate a multiple
wiring network. [2] Structurally, this type of coordination requires strict perpendicular
arrangements of the ligand planes at each metal centre (Figure 3). Given such a coordination
environment around the metal centres, the linear and rigid extension of the ligand system from
mono- to multitopicity will automatically lead to a grid-like two-dimensional coordination
network with regularly arrayed metal ions. According to this general “leitmotif”, grid-like
metal ion arrays can in principle be prepared by careful prearrangement of the subunits using
any set of metal ions and organic ligands possessing compatible coordination features. This
requires ligands containing either bidentate or tridentate binding subunits in combination with
metal ions possessing tetrahedral or octahedral (and in some cases bipyramidal) coordination
geometry, respectively. General design principles for these structures involve
thermodynamically driven synthesis of complex discrete objects from numerous molecular
components in a single overall operation.
The construction of higher-order molecular architectures concerns the processes
underlying the progressive complexification of matter through self-organization. The
generation of organization levels of increasing complexity, diversity and functionality relies
on a set of basic building blocks and subunits, interconnected through a multitude of
relatively weak, non-covalent interactions (e.g. herein coordinative bonding, etc.) and rests on
the progressive build-up of more and more complex entities by multiple, sequential and
hierarchical self-organization steps that follow a conditional pathway, each step setting the
base for the next one.
In recent years, more and more powerful self-assembly strategies have been developed
for the controlled access to a variety of nano-sized objects of increasing complexity. Guided
by the structural theme of the [2x2] metal ion array, we report herein on the hierarchical self-
assembly of supramolecular architectures, which generate in a first self-assembly step new
properties based on the spin-transition phenomenon and modulate this newly gained
“collective” property during a second, higher ordered, self-assembly step (see chapter 6.1.).
The structural organisation follows a component-module-architecture-hierarchy of increasing
complexity (Figure 4).
11