Crystal Structures and Spectral Investigation of Aroylhydrazones and their Mixed Ligand Metal Chelates

Supra molecular architectures of coordination complexes of liydrazones through non covalent interactions have been explored. Molecular self—assernbly driven by weak interactions such as hydrogen— bonding, K '”T[, C-1-I‘ "TE, van der Waals interactions, and so forth are currently of tremendous research interest in the fields of molecule based materials. The directional properties of the hydrogembonding interaction associate discrete molecules into aggregate structures that are sufficiently stable to be considered as independent chemical species. Chemistry can borrow nature’s strategy to utilize hydrogen-bonding as Well as other noncovalent interactions as found in secondary and tertiary structures of proteins such as the double helix folding of DNA, hydrophobic selflorganization of phospholipids in cell membrane etc. In supramolecular chemistry hydrogen bonding plays an important role in forming a variety of architectures. Thus, the wise modulation and tuning of the complementary sites responsible for hydrogen—bond formation have led to its application in supramolecular electronics, host-guest chemistry, self-assembly of molecular capsules, nanotubes etc. The work presented in this thesis describes the synthesis and characterization of metal complexes derived from some substituted aroylhydrazones. The thesis is divided into seven chapters.

Studies on Transition Metal Chelates of some Tridentate Aroylhydrazones

The ability of aroylhydrazones to bind with transition metals is a developing area of research interest and the coordinating properties of hydrazones can be tuned by the appropriate choice of parent aldehyde or ketone and the hydrazide. So in the present work we selected four different aroylhydrazones as principal ligands. Introduction of heterocyclic bases like 1,10-phenanthroline, 2,2′-bipyridine, 3-picoline and pyridine leads to the syntheses of mixed ligand metal chelates which can cause different bonding modes, spectral properties and geometries in coordination compounds. The importance of aroylhydrazones and their complexes in various fields and their interesting coordinating properties stimulate our interest in the investigation of transition metal chelates with four different aroylhydrazones. The aroylhydrazones selected are 4-benzyloxy-2-hydroxybenzaldehyde-4-nitrobenzoylhydrazone dimethylformamide monosolvate, 5-bromo-2-hydroxy-3-methoxybenzaldehyde nicotinoylhydrazone dihydrate methanol monosolvate, 4-diethylamino-2- hydroxybenzaldehyde nicotinoylhydrazone monohydrate and 2-benzoylpyridine- 4-nitrobenzoylhydrazone. The selection of 4-benzyloxy-2-hydroxybenzaldehyde- 4-nitrobenzoylhydrazone was based on the idea of developing ligands having D-π-A general structure, so that the proligand and metal complexes exhibit NLO activity. Hence it is interesting to explore the coordinating capabilities of the synthesized hydrazones and to study the NLO activity of hydrazones and some of the metal complexes.