Self-assembled Transition Metal Coordination Frameworks of ...

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The work presented in this thesis comprises synthesis and characterization of
suitably substituted thiocarbohydrazone and carbohydrazone ligand building blocks,
self-assembled metallosupramolecular square grid complexes of Ni(H), Mn(H), Zn(H)
and Cd(H) as well as some di/multinuclear Cu(Il), Mn(H) and Zn(II) complexes. The
primary aim was the deliberate syntheses of some novel transition metal framework
complexes, mainly metallosupramolecular coordination square grids by self-assembly
and their physico-chemical characterization. The work presented, however, also
include synthesis and characterization of four mononuclear Ni(II) complexes of two
thiosemicarbazones, which we carried out as a preliminary and supporting study.
In addition, the study of the coordinating preferences of thiocarbohydrazones
and carbohydrazones towards selected first row transition metals, including
magnetically important nickel, manganese and copper, provides an idea of the control
over the topology of complexes can be achieved by the these ligand building blocks
and probable similar kinds of ligands. Since the properties of any material are largely
due to its structure, control over the topology sometimes allows to manipulate these
properties. This allows the deliberate design of materials with a range of useful
properties, including electronic properties, magnetic properties, non-linear optical
effects luminescent properties, etc.
A variety of factors can influence the self-assembly process. Basically, the
design of proper ligands as building blocks, together with the coordination preferences
of the metal centers as nodes, is undoubtedly the most rational synthetic strategy in
manipulating the framework topologies. The key step thus includes syntheses and
characterization of useful ligands. We have designed three thiocarbohydrazone and
three carbohydrazone ligands for this purpose. Additionally, two lower homologue
thiosemicarbazone ligands were also prepared. The ligands synthesized were:
1. 1,5-Bis(di-2-pyridyl ketone) thiocarbohydrazone (H2L')
2. 1,5-Bis(2-benzoylpyridine) thiocarbohydrazone (HZLZ)
3. l,5-Bis(quinoline-2-carbaldehyde) thiocarbohydrazone (HZL3)