Rational Design of Polynuclear Organometallic Assemblies from a Simple Heteromultifunctional Ligand

In
modern coordination chemistry, supramolecular coordination complexes
take advantage of ligand design to control the shapes and sizes of
such architectures. Here we describe how to utilize starting building
blocks and a multifunctional ligand to rationally design and synthesize
different types of discrete assemblies. Using a hydroxamate ligand
featuring two pair of chelating sites together with half-sandwich
iridium and rhodium fragments, we were able to construct a series
multinuclear organometallic macrocycles and cages through stepwise
coordination-driven self-assembly. Experimental observations, supported
by computational work, show that selective coordination modes were
ascribed to the significant electronic density differences of the
two chelating sites, (O,O′)
and (N,N′). The results underline
the advantages of the discrimination between soft and hard binding
sites, and suggest that hydroxamic acids can be used as a versatile
class of facile multifunctional scaffold for the construction of novel
two-dimensional and three-dimensional architectures.