A novel series of Cu(II) complexes of azo rhodanine derivatives (HL_n) have been prepared and characterized by thermal analysis, spectral studies (IR, mass, UV-Vis, ESR) and magnetic measurements. IR spectra suggest that the HL_n acts as a bidentate ligands coordinating via (NN) and deprotonated enolized carbonyl oxygen (-C-O-). ESR spectra of the Cu(II) complexes show d_{x 2- y 2} as a ground state, suggesting tetrahedral distorted or square planar geometries around Cu(II) center. The X-ray diffraction (XRD) patterns powder forms of Cu(II) complexes shows many diffraction peaks which indicates the polycrystalline phase. Thermal properties and decomposition kinetics of compounds are investigated. The thermodynamic parameters and evaluation of kinetic parameters (E_a, ΔS^∗, ΔH^∗ and ΔG^∗) of thermal decomposition stages have been evaluated using Coats-Redfern and Horowitz-Metzger methods. Cu(II) complexes are screened for their biological activity against bacterial and fungal species. The Cu(II) complexes showed antimicrobial activities against Staphylococcus aureus and Penicillium italicum.