Foldameric Aspects of Triazine-Hydrazone Ligands and their Complexes

Abstract

Foldameric ligands containing alternating triazine and pyridine (trz-py) sequences linked by hydrazone (hyz) groups and terminated by hydroxymethyl groups have been synthesized. The major focus of this thesis comprises of the synthesis of such ligands and their metal ion complexes using Pb(II), Zn(II), and Ag(I) metal ions. The foldameric behaviour of the native ligands and their complexes in solid state and solution phase has been studied using primarily NMR and X-ray diffraction analyses. The thesis also describes the presence of Pb-π interactions observed in Pb(II) complexes of subcomponents of these ligand strands. Chapter one describes the self-assembly processes pertaining to supramolecular chemistry. Foldons based on py-py interactions and their evolution to include the interactions between other heterocyclic ring units (containing N-donor atoms) and hyz groups have been described. A literature overview of the shape/volume change based on such foldons in their complexed and decomplexed states has been described. Duality codons based on trz-hyz sequences have been described and their potential uses for incorporation into co-polymer gels for the purpose of actuation have been proposed. Chapter two mainly describes the design, and synthesis of the hydroxymethyl terminated trz-hyz strands (Lp3, Lp5, Lp7, Lb3, Lb5, and Lm5), where the number indicates the heterocyclic units in each strands and the letter p, b, m stands for the trz-substituents such as phenyl, t-butyl, and methyl groups, respectively. The foldameric studies of these ligands using primarily NMR and X-ray diffraction techniques have been reported. Chapter three describes the study of various metal ion complexes of the ligands of Chapter two. The Pb(II) ion has been mainly employed for obtaining complexes followed by Zn(II), Ag(I) and only two of the complexes were based on Co(II) ions. The foldameric aspects of such complexes and the detailed structures based on NMR and X-Ray diffraction analyses have been investigated. Chapter four describes the Pb(II)-π(aryl) interactions that were observed in the complexes of the sub-component ligands Lp and L2. Synthesis and characterization of such Pb(II)-π interaction exhibiting complexes and an investigation of the forces influencing such interactions have been reported. Moreover, a relatively uncommon bifurcated type of Pb(II)-π interaction was surveyed. Complexes exhibiting such interactions from present work have been reported. Chapter five describes the conclusive highlights of the thesis. Additionally, future directions for the major and minor projects have been envisaged.