Syntheses and structural characterization of Cu-TPY ternary complexes with nucleotides and its constituents

Abstract

Syntheses and Structural Investigations of Cu(II) Ternary Complexes of Nucleotide and its Constituents with Terpyridine. The major interest in the field of metal-nucleic acid chemistry arises due to the crucial role of metals in DNA stabilization [Zn(II),Mg(II)],destabilization[Cu(II),Co(II),Cd(II)],mutagenisis and also in a variety of enzymatic processes. Nucleotides, the constituent of nucleic acids contain a variety of sites for interaction with metal ions, from electrostatic interactions with the anionic phosphate backbone to soft nucleophilic interactions with purine heterocycles. Since there are different nucleotides, they furthermore offer a range of steric factors to explore. Our investigation involves synthesizing several ternary Metal- Nucleotide coordination complexes to explore its specificity in metal binding involving tridentate auxiliary ligand. This thesis offers the syntheses and structural insights of metal ternary complexes with nucleotides and their constituents. In the first chapter, a series of ternary complexes of Cu (II)-TPY-5'-Nucleotide Monophosphate have been synthesized and characterized with single crystal XRD. Structural investigations reveal the formation of homo base pairs (A-motif) in ternary complex of 5’AMP and the presence of TPY ligand provides stacking interactions leading to the formation of few interesting supramolecular assemblies. In the second chapter, the specificity of metal binding in 2’ and 3’ nucleotides are explored by using 2'-GMP, 2'-AMP, 2'-CMP, 2'-UMP, and 3'-GMP. These molecules due to the change in phosphate group position provide different binding sites compared to their 5’ counterparts as expected. In the third chapter, there are two parts dedicated for deoxy nucleotides and nucleosides. In the first part, due to the absence of 2’ oxygen atom in the sugar ring for deoxy nucleotides the specificity of metal binding in these complexes are considered and in part B, the nucleoside complexes are examined where the phosphate groups are absent. A comparative structural discussion has been made in the subsequent chapter to get an idea about the sugar ring conformation, nucleobase conformation and interaction of guest of water molecules in the structural stability of these complexes. Conformation of most of the nucleobase conformations about the glycosyl bond are anti, although in a few cases, preferred conformations are syn. The sugar moieties are found to exhibit C2'/C3', endo/exo conformation. The last chapter presents the ternary coordination complexes of Cu (II) with nucleobases. Here six different nucleobase complexes are synthesized in different reaction conditions and unusual coordination modes of these complexes are discussed in detail. In all the above complexes, the role of water molecules and counterions like perchlorate, nitrate, sulphate is discussed in depth. The effect of π-π stacking interactions between the molecules in these systems are presented in a descriptive manner which leads to formation of different supramolecular assemblies.