Self-Assembly Principles of Helicates - Metallofoldamers: Supramolecular Architectures from Helicates to Biomimetics - page 118

Figure 3.20 Effect of secondary interactions on self-assembly processes. (a) Formation of the
pentanuclear helicate templated with Cl anion. Reprinted with permission from [ref 53]
Copyright 1996 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. (b) Effect of stabilizing
Ag þ interaction on the formation of triple-stranded helicates. Reprinted with permission from
[ref 56] Copyright 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
are introduced for mononuclear coordination compounds and subsequently extended to
metallo-organic supramolecular compounds, where intramolecular reactions addition-
ally take place. The phenomenological understanding of self-assembly processes was
oftenhinderedbysupramolecularterminologyandseveralcommonlyusedconcepts
have been adequately rationalized only recently. This is the case of cooperativity and
intramolecular macrocyclization processes, for instance. A deeper understanding of
these chemical tools was stimulated by the development of predictive strategies for
designing functional edifices. The fastidious effort resulted in the elaboration of power-
ful thermodynamic models that quantitatively identified key energetic factors governing
the self-assembly processes.
Helicate assemblies play a crucial role in the above evolution. These compounds were
often used as model assemblies for structural, thermodynamic and kinetic investigations.
A relative abundance of previously collected data permitted more sophisticated analyses
to be carried out in order to develop thermodynamic modelling. Future initiatives in this
field should be focused on acquiring physico-chemical data that are still relatively scarce
for three-dimensional nanostructures. This will allow an improvement of the present ther-
modynamic description and its adaptation for predicting advanced supramolecular archi-
tectures. In spite of this considerable effort, some supramolecular assemblies may still
escape the predictive design due to some unexpected conformational and coordination
preferences, or the chemist's choice of inappropriate structural elements.