INTRAZEOLITIC REACTION BETWEEN TRANSITION-METAL IONS AND OPEN OR CLOSED POLYAMINE LIGANDS

Intrazeolitic transition metals, such as Ni2+ and Co2+, were chelated by open or closed, tetra- or pentadentate polyamine ligands. Their coo rdination and redox chemistry was studied by IR-Raman, EPR, diffuse re flectance. and magnetic techniques. For pseudo-octahedral complexes wi th tetradentate ligands, the presence of the zeolite favors cis coordi nation over the trans form. This is explained by the very low tendency of the zeolite surface to bind as a monodentate ligand to a planar me tal complex. However, if trans complexes are formed (as with Ni2+), th e axial positions on the complex are available for ligand exchange. Su ch intracrystalline complex syntheses result in the formation of new r edox solids. For example, [Co-II(cyclam)](2+)-NaY (cyclam = 1,4,8,11-t etraazacyclotetradecane) is a reversible, high-affinity (p(1/2) <1 mba r) and high-capacity (> 90 mu mol g(-1)) dioxygen-sorbing material.