The work presented in this Thesis consist of two parts. In the first part, a new bidentate ligand, N -(5-methyl-thiazole-2-yl) quinolone carboxylic acid (HMetzq) was synthesized by a green ionic liquid-based method using tetrabutyl ammuniom bromide (TBAB) in order to develop a new approach for removing the dangerous pyridine and for improving the reaction time and yield. The following complexes were then synthesized using this ligand and cobalt (II) and copper(II) salts. 1) [Co 2 (Metzq) 2 (OAc) 2 ].2H 2 O 2) [Cu 2 (Metzq) 2 (OAc) 2 ].H 2 O The structure and spectral properties of the ligand and the synthesized complexes have been investigated by UV-Vis, FT-IR, X-ray, 1 H NMR and elemental analysis. The structure of the cobalt and copper complexes was determined by X-ray crystallography. The coordination geometry around the central metal ion in these complexes is a distorted octahedral. In the second part, a new tetradentate ligand, N,N' -bis (1-hydroxy-2-naphtocarboxamide)-2-aminobenzylamine (H 4 Hynabza) and the novel bidentate ligand, N,N' -bis (2-naphtocarboxamide)-2-aminobenzylamine (H 2 nabza) were synthesized by a green ionic liquid-based method using tetrabutyl ammuniom bromide (TBAB). To investigate the possibility of the application of these new ligands as sensors for detection of biologically important ions, the absorption and florescence spectra of these ligands were obtained. The spectral properties of these ligands, i.e. H 2 nabza and H 4 Hynabza were investigated in the absence and presence of different metal ions. The results show that these ligands can be used as a turn-off fluorescent sensor for detection of Fe 3+ ions with high selectivity and sensitivity compared to other metal.