Chemistry - a European Journal vol:1 issue:2 pages:144-149
Intrazeolitic transition metals, such as Ni2+ and Co2+, were chelated by open or closed, tetra- or pentadentate polyamine ligands. Their coordination and redox chemistry was studied by IR-Raman, EPR, diffuse reflectance. and magnetic techniques. For pseudo-octahedral complexes with tetradentate ligands, the presence of the zeolite favors cis coordination 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 metal complex. However, if trans complexes are formed (as with Ni2+), the axial positions on the complex are available for ligand exchange. Such intracrystalline complex syntheses result in the formation of new redox solids. For example, [Co-II(cyclam)](2+)-NaY (cyclam = 1,4,8,11-tetraazacyclotetradecane) is a reversible, high-affinity (p(1/2) <1 mbar) and high-capacity (> 90 mu mol g(-1)) dioxygen-sorbing material.