The work presented in this Thesis consist of two parts. In the first part, new carboxamide ligands N-(thizazol-2-yl) picolinamide (Htp) and 1-hydroxy-N-(quinolin-8-yl) naphthalene-2-carboxamide (H 2 hqn) were synthesized by bengin method using ionic liquid as the reaction medium. Four new Zn(II), Cd(II), Mn(II) and Mg(II) complexes of Htp ligand were synthesized. The purity and spectral properties of the ligand and its Zinc, Cadmium, Manganese and Magnesium complexes have also been investigated by UV-Vis, FT-IR and elemental analysis. The structure of complexes were determined by X-ray crystallography. The coordination geometry around the central metal ion in these complexes is a distorted octahedral. The unit cell of these crystals contains disordered molecules of ethanol. The Thermal behavior of zinc complex was studied by TG-DTG-DSC. The ZnO nanoparticles were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray (EDX), Fourier transform infrared (FT-IR) and ultraviolet–visible (UV–vis) spectroscopy. In the second part, the optical properties of the ligand,N?-bis(pyridine-2-carboxamido)-4,5-dimethylbenzene (H 2 Me 2 ), N,N?-bis(pyridine-2-carboxamido)-4-methylbenzene (H 2 Me) and H 2 hqn have been investigated by UV–vis spectroscopy and molecular fluorescence spectroscopy. The optical behavior of H 2 Me 2 and H 2 Me ligands in the presence of different metal ions shows that both ligands can be used as colorimetric sensors for detection of Cu 2+ with high selectivity and sensitivity compared to other metal ions. The absorption and emission behavior of ligand H 2 hqn in the presence of different metal ions were studied. The results show that this ligand can be used as a turn-off fluorescent sensor for detection of Cu 2+ ions with high selectivity and sensitivity compared to other metal.