The book entitled "Supramolecular structures and applications of azo rhodanine complexes" comprises five main Chapters. The objectives of the present book are: (1) The synthesis of the ligand 5-(2,3-dimethyl-1-phenylpyrazol-5-one azo)-2-thioxo-4-thiazolidinone (HL). (2) The molecular structures of the ligand tautomers were discussed. (3) The synthesis of M(II) complexes derived from this ligand and characterization by elemental analysis, spectral studies, molar conductance and magnetic measurements as well as thermal analysis studies. (4) Study the antimicrobial activity of (HL) and it's Cu(II) complexes. (5) Study the effect of the ligand (HL) as inhibitor for the corrosion of carbon steel in 2 M HCl solution. (6) Study the thermal, dielectric properties and ac conductivity of the ligand (HL) and its metal complexes with copper(II), cobalt(II) and nickel(II). (7) The effect of metal ion variation on the thermal activation energies of decomposition, thermal activation energies ofelectrical conductivity and conduction mechanism were discussed.