Shaping distinct magnetic interactions in molecular compounds

► Nine new oxalates, with 3d elements, showing interesting characteristics were synthesized. ►The oxalate units and the positive or negative groups have induced various magnetic properties. ► The Mössbauer data revealed two different positions for each valence state of iron in molecule. ► There is a competition of anti-ferromagnetic couplings inside the magnetic units and between them. ► An overall ferri-magnetic long range ordering was demonstrated unambiguously.