Self-assembled Transition Metal Coordination Frameworks of ...

__ Introduction
1.2. Coordination frameworks - A brief introduction
ln the intervening period of coordination chemistry, which marked from
Alfred Werner’s seminal article ‘Beitrag zur Konstitution anorganischer
Verbindungen’ ['7], this discipline has metamorphized from the province of inorganic
chemists to the domain of a broad constituency of researchers, ranging from
biochemists to materials scientists [8]. The chemistry of multinuclear coordination
metal complexes, especially coupled systems is of special interest in various fields of
science including physics, material science, biotechnology, etc. The main reason
probably due to the phenomenon of interaction between metal centers lies at the
crossover point of two widely separated areas, namely the physics of the magnetic
materials and the role of polynuclear reaction sites in biological processes [9]. The
growth of coordination chemistry has been three dimensional, encompassing breadth,
depth, and applications. The spawning of, or key roles in, new fields is an inevitable
consequence of the foundational position of coordination chemistry in the chemical
sciences. Complexes containing two or more metal ions are of increasing interest
because of their relevance to biological systems also, as evidenced by the many
multinuclear complexes in biology [10]. Conversely, in the last two decades, reports
of various self-assembled supramolecular transition metal architectures have made a
great stimulus in the modern inorganic chemistry in general, and supramolecular
coordination chemistry in particular. The past decade has seen a proliferation in the
reports of complexes displaying distinct, nonsimple architectures. For example,
coordination compounds exhibiting motifs reminiscent of grids, racks, ladders,
triangles, squares, hexagons and other polygons, various polyhedra/boxes, cylinders,
rods, metallodendrimers, coordination oligomers, rotaxanes, catenanes, knots, circular
helicates, etc are known today [ll]. The definition of coordinate bonds as
supramolecular interactions tends to be limited to those cases where they result in
particularly unusual or elaborate molecular architectures [12]. The self-assembly
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