This thesis has been prepared in three sections: The first section of this thesis, includes the results of our efforts on the synthesis and characterization of Cu(I) complexes using tetradentate Schiff base ligands, exhibiting different flexibilities. First, thio2dapte (2) was synthesized using the very flexible starting bis amine (dapte), and its conformational habit and coordination mode in the resulting complexes, 3-7, was investigated. [Cu((thio)2dapte)]ClO4 (3) [Cu2(µ-CN)2(µ-(thio)2dapte)]n (4) [Cu2(µ-SCN)2(µ-(thio)2dapte)]n (5)[CuCl(thio)2dapte] (6) [CuBr(thio)2dapte] (7) In continuation of this work, the Cu(I) complexes of two Schiff base ligands (with disulfide bond), phca2phds (9) and ca2phds (13), were synthesized: [Cu2(?-phca2phds)2](ClO4)2 (11)[Cu2(?-phca2phds) (?-I)2] (12) [Cu2(?-ca2phds) (?-I)2] (15) These complexes were characterized by elemental analyses, FT-IR, UV-Vis, 1H NMR spectroscopy and further investigated by cyclic voltammetry. The crystal structures of (3), (4), (5), (11) and (13) were determined by single crystal X-ray diffraction. The coordination geometry around the Cu(I) center in all complexes is a distorted tetrahedral. Interestingly, the ligands show versatile conformational and coordination characteristics under different conditions due to their flexibility. The flexible N2S2 Schiff-base ligand (thio)2dapte acts as a tetradentate ligand in (3) while it acts as a bis-bidentate bridging ligand via one S atom and one N atom in (4) and (5). In these complexes the pseudohalide ligand act as a bridge between two metal centers. In complex (11), the Schiff base ligand, phca2phds, acts as a N2S2 bis-bidentate chelating ligand coordinating to two Cu(I) centers. The effect of halide and pseudohalide ligands on redox potential of complexes 3-7 has been investigated by cyclic voltammetry. In the second part of the thesis, described are the syntheses of Zn(II) complexes using potentially tetradentate, N2S2 ligands, containing a disulfide bond: phca2phds (9), ca2phds(13), (4-NO2bz)2phds (16) and thriam [1]. Surprisingly, these ligands undergo reductive disulfide bond scission upon reaction with Zn2+ in alcoholic media to give the respective Zn(NS)2 complexes, (10), (14), (17), (18), where these ligands are the corresponding bidentate thiolate anions: [Zn(phca2pht)2] (10)[Zn(ca2pht)2] (14) [Zn((4-NO2bz)2pht)2] (17)[Zn2(dmdtc)2(?-dmdtc)2] (18) These complexes were characterized by elemental analyses, FT-IR, UV-Vis, 1H NMR spectroscopy and further investigated by cyclic voltammetry. The crystal structure of (10), (14), and (18) have been determined by single crystal X-ray diffraction. These structures clearly show that the potentially tetradentate ligands have undergone scission of the disulfide bond to give two NS bidentatethiolate ligands coordinated to the Zn(II). The coordination geometry around Zn(II) centers in these complexes is a distorted tetrahedron. In addition, DFT calculations (B3LYP/LANL2DZ/6-311++G(d,p)) support the structure of 10 and 14. Cyclic voltammetric studies demonstrate that Zn(II) shifts the reduction potential of the disulfide ligands to less negative values thus making them more susceptible to reductive cleavage of the disulfide bond. The results of semi-empirical PM6 calculations offer key insight into the nature of the transition state for this reaction. In the third part, the synthesis of new azido-bridged complexes with two unsymmetrical Schiff base ligands, H2salabza (20), and H2Me-salabza (24), is reported: [MnIII(salabza)(µ-1,3-N3)]n (21) [CuII4(salabza)2(µ-1,1-N3)2(N3)2(HOCH3)2],(22) [Fe(salabza)(?-N3)]n (23) [Mn(Me-salabza)(?-N3)] (25) These complexes have been fully characterized by X-ray structural analyses, and spectroscopic and electrochemical methods, In complex (21) each manganese(III) atom is coordinated to N2O2 donor atoms from salabza and two adjacent Mn(III) centers are linked by end-to-end (EE) azide bridge to form a helical polymeric chain with octahedral geometry around the Mn(III) centers. Complex (22) is a centrosymmetric tetranuclear compound containing two types of Cu(II) centers with square pyramidal geometry. Each terminal copper atom is surrounded by N2O2 atoms of the salabza, and the oxygen atom of methanol. Each central copper(II) ion is coordinated to two phenoxo oxygen atoms from one salabza, one terminal azido, and two end-on (EO) bridging azido ligands. The central copper(II) ions are linked to each other with two end-on (EO) azido groups.