Intrazeolite Complexation of Transition Metal Ions by Triazacyclononane-Type Ligands:  Control of Cluster Nuclearity and Oxygen Binding in Confined Reaction Spaces

1,4,7-Triazacyclononane (L) and its methylated analog (L‘) form complexes with zeolite-exchanged Mn 2+, Co 2+, or Cu 2+ . Through comparison with diluted solutions of the complexes, the effect of the zeolite environment on the complex formation was evaluated. In the case of Mn 2+, the complexation was monitored by observing the zero-field splitting in the X- and Q-band ESR spectra of the Mn 2+ ion. Adsorption of L into metal Y zeolites yields bis L complexes; the L‘ mono complexes are formed. The latter complexes are not coordinated by the zeolite surface, as deduced from the spectral parameters of the [Mn(L‘)] 2+ and [Cu(L‘)] 2+ complexes. Mono [Co(L‘)] 2+ in the zeolite is a reversible dioxygen binder, a property not previously documented for these complexes in solution. Exposure of [Mn(L) 2 ] 2+ or [Mn(L‘)] 2+ containing Y zeolites to H 2 O 2 results in intraporous formation of oxidized Mn dimers. The constrained zeolite environment seems to stabilize the oxidized dimers of Mn and L by preventing further cluster expansion.