Macrocyclic systems; Otherwise known as cyclophanes are the most regarded chemical compounds and substances in biochemical and medicinal chemistry of the last decades. Their role in understanding molecular processes in biochemical system, material science, encapsulation, catalysis, hydrometallurgy, activation, separation transportation phenomenon among many other important roles had made them attract greater attention in both science and medical fields of research and studies [1-8]. Paraquat type of macrocyclic compounds have also been studied in view of their host-guest chemistry , redox behaviour , catalytic activity , and incorporation into supramolecular architectures.
Macrocyclic compounds have also been designed as special ligands to mimic the function of natural carrier molecules in recognizing and transporting specific metal cations, anions or neutral molecules and in understanding and reproducing the catalytic activity of metallo-enzymes and proteins [1–8].
A large number of macrocyclic compounds have been synthesized to specifically identify the role played by the different donor atoms, their relative position, the number and size of the chelating rings formed, the flexibility and the shape of the coordinating moiety on the selective binding of charged or neutral species and on the properties arising from these aggregations [12-13]
The study of hetero macrocyclic systems is of great interest both from the theoretical and practical point of view. Hetero macrocyclic compounds also play an important role in the design and discovery of new physiological pharmacologically active compounds. These compounds constitute the structural frameworks of several naturally occurring alkanoids that show a wide range of pharmaceutical and industrial importance .
Metal complexes of macrocyclic systems; Emphasis was given to the coordination of various macrocyclic phane systems with certain metal ions in both the lanthanide and the transition series to produce complex compounds of desired medical and pherceutical importance.
Heterocyclic compounds incorporated in a macrocyclic ring provide rigidity and are able to participate in complexation through their soft donor atoms; for example macrocyclic ethers with pyridine and other nitrogen containing heterocyclic subunits were reported to form strong and selective interactions with various charged and neutral guest molecules [15-19]
Many of such macrocyclic ligand-metal complexes otherwise called organometalics had achieved positive application in medical diagnosis and treatments. For example, Gadolinium complexes of certain macrocyclic ligands are used in hospitals to improve the contrast of magnetic resonance images (MRI) . Manganese macrocyclic complexes have achieved significant progress owing to the increase recognition of Mn (II) functions in biological system [20-21].
The stability of macrocyclic metal complexes depends upon a number of factors,...