Magneto structural characterization of polynuclear complexes with supramolecular architectures The thesis describes the supramolecular organization of homo and heteropolynuclear complexes containing different paramagnetic centers going from d block metal ions to combination of d f spin carriers topologies. These polynuclear complexes have been structurally and spectroscopically characterized and partly magnetostructural correlations have been performed. The synthesis of polynuclear complexes has been based on self assembly and rational strategies. Iron(iii) aza crown complexes have been isolated through self assembly reaction between N imidazol 2 yl salicyloyl hydrazide and FeX3·xH2O salts in presence of pseudo halide coligands. These complexes are characterized by antiferromagnetic coupling between the Fe(iii) centers. In addition self assembly of easy accessible Schiff base ligands and d block metal salts led to homo polynuclear d complexes with the magnetic interaction varying from strong antiferromagnetic coupling between the paramagnetic centers to ferromagnetic interaction induced by accidental orthogonality of the magnetic orbitals associated to d metal ions in partial cubane structural core. The rational strategy approach is divided in two subcategories namely the dendritic approach and ʺcomplex as ligandʺ strategy. The dendritic approach is based upon C3 symmetric triaminoguanidine Schiff base ligand derivatives which present three fold tridentate coordination pockets.