The preparation of Bis[2-(6-methoxynaphthalen-2-yl)propanoate] chelate complexes with nickel(II), copper(II), zinc(II), cadmium(II) and tin(II) were described in this thesis. Infrared, ultraviolet–visible, spectrophotometric techniques, magnetic susceptibility, atomic absorption, conductivity measurements and melting point were used to characterize the free ligand and the above chelate complexes. All these complexes were found to act as stabilizer in PVC films. The light of wavelength (313 nm) with intensity of (1.052×10-8 ein.dm-3.S-1) was used for irradiation of polymer films at room temperature. The rate of photodegradation and photostabilization of PVC film (thickness 30 m) were monitored by measuring the carbonyl, polyene, hydroxyl and chlorine indices (Ico, Ipo, IoH and Icl) values as a function of irradiation time and ultraviolet–visible spectrophotometry using 0.5% wt/wt concentration of stabilizer. It was found that the carbonyl index (Ico), polyene index (Ipo) and hydroxyl index (IoH) values increased with irradiation time, while the chlorine index (ICl) values decreased with irradiation time, and this increase depend on the type of additives (free ligand and complexes). The following trend was obtained for the photostabilization effect of PVC film in presence of these additives: Cd(L)2 > Zn(L)2 > Sn(L)2 > Ni(L)2 > Cu(L)2. According to the experimental results obtained several mechanisms were suggested depending on the structure of the additives. Among these mechanisms, HCl scavenging, UV absorption, peroxide decomposer and radical scavenger for photostabilizer additives. The mode of chain scission was also investigated by measuring the variation of average viscosity molecular weight with irradiation time for PVC films with and without additives. It was found that the values of the variation of average viscosity molecular weight decreased with increasing irradiation time