Abstract: The invention relates to polyazacycloalkanes having 3, 4 or 5 nitrogen atoms, tri-, tetra- or penta-azamacrocyclic transition metal complexes and processes for the production of said polyazacycloalkanes. The object of the invention is to form polyazacycloalkanes able to trap metal cations and in particular U, Pu, Am, Ce, Eu, Al, Gd, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ag, Cd, Sn, Au, Mg or Pb or complexes able to trap in particular oxygen in a gaseous mixture. The invention more particularly applies to the treatment of liquid effluents from nuclear power stations.