Abstract: The present thesis deals with the synthesis of new Co(II), Ni(II), Cu(II) and Zn(II) transition metal complexes and the azo group-containing Schiff base ligands via the condensation reaction of 3-amino-1-propanol and substituted 2-aminopyridine with the azo-coupled salicylaldehyde. Elemental analyses, mass spectrometry, magnetic studies, 1H-NMR, 13C-NMR, electronic and infrared data suggest mono-nuclear structure for the metal complexes. The chromogenic behavior of the receptors (L1 and L2) toward various anions and cations were investigated by UV-Vis titration and 1HNMR spectroscopy. The L1 chemosensor showed visual color changes towards Al3+ , Cu2+ , Fe3+ and Cr3+ cations, in DMSO/water (9:1) solution. This receptor also reveals visual changes toward CN¯ anion in aqueous media. No significant color changes were observed upon the addition of any other anions such as F¯, Cl¯, Br¯, AcO¯, H2PO4¯, HSO4¯, ClO4¯, N3¯, NO2¯, SCN¯. UV-Vis, FT-IR, 1H-NMR experiments and computational studies were conducted to investigate the nature of interaction between receptor with CN¯ anions through nucleophilic addition and hydrogen bonding interaction. The L2 chemosensor displays visual changes towards anions like F¯, H2PO4¯ and AcO¯ and also towards cation such as Zn2+ in DMSO. The H2L1–H2L3 receptores were used for the detection of Hg2+, Cd2+ and F¯. The binding constant (Ka) and stoichiometry of the host–guest complex formed were determined by the Benesi–Hildebrand (B–H) plot and Job's plot method, respectively. In the computational section, quantum chemical calculations were performed to analyze the effect of cooperativity in lithium bonding on the strength of hydrogen bonding in (LiCN)n…HX clusters, (n=1–5, X= F, Cl) at the MP2/ 6-311++G(d,p) computational level of theory. The results reveal that strength of hydrogen bonding is enhanced due to cooperativity between lithium bonded clusters. These effects are studied in terms of structural, energetic, and dipole moment pr
