Chemistry Reference
In-Depth Information
Figure 4.1
Historical evolution of the metal-nucleobase structures deposited on the CSD
database. Each colour represents a year of that decade
The aim of this chapter is to provide an overview of supramolecular aspects of
transition metal-nucleobase chemistry. This is not an exhaustive review, but rather
summarizes the structural possibilities that have been described through the com-
bination of these two types of components: metal ions and nucleobases. As well as
this, a brief overview of the biological, chemical and physical properties of these
compounds is given.
The formation of a particular supramolecular architecture requires the selec-
tion of suitable building blocks. Supramolecular systems require their components
to have appropriate spacing and confi guration relative to each other, and ideally a
library of related structural units is required. The structural subunits for the con-
struction of coordination supramolecules are the metal ions, or complexes, and
organic ligands. Architectures based on these systems have been the subject of
numerous investigations due to their potential for applications based on their useful
properties, such as molecule and ion hosts, optical properties, porous materials and
catalytic activity.
3
Geometrical aspects have a critical role in determining the fi nal architecture of
the supramolecular entity. Specifi cally, in the case of metal ions (or complex frag-
ments) and nucleobases two different types of building blocks are used for con-
structing fi nite or infi nite molecular assemblies; the most typical syntheses proceed
in a single step by self-assembly, however, in a few cases multistep synthetic
approaches have been shown more convenient, i.e. nonlabile metal fragments.
4.1.1 Nucleobases as Building Blocks
Nucleobases are ideally suited as building blocks for supramolecular coordination
chemistry due to their versatility as ligands. The most relevant factors in this respect
are: (i) the large number of donor sites available for metal binding, (ii) the H-
bonding donor/acceptor sites and (iii) the potential for p
-
p stacking, analogous to
