Interaction of tetrameric silver with ammonia in AgCs-rho zeolite

Cationic silver clusters formed in gamma -irradiated AgCs-rho zeolite have been studied by EPR spectroscopy. Tetrameric silver is formed efficiently i n the dehydrated form of zeolite as well as in samples exposed to ammonia. However, the hyperfine splitting of the Ag-4(3+) pentet in AgCs-rho/NH3 zeo lite is distinctly smaller due to the shift of spin density from silver to nitrogen nuclei, suggesting the formation of an Ag-4(3+)-ammonia complex. T he observed N-14 and N-15 superhyperfine splitting from interacting (NH3)-N -14 and (NH3)-N-15 molecules unequivocally proved the presence of a multico re Ag-4(3+)(NH3)(n) complex. Based on the simulation of N-14 and N-15 super hyperfine interactions a structure of the complex was proposed in which two ammonia molecules are located close to the octagonal windows of two neighb oring alpha -cages and four further molecules are placed in next-neighborin g alpha -cages interacting with the Ag tetramer through square windows. Whe n dehydrated AgCs-rho zeolite containing radiation-induced Ag-4(3+) cluster s is exposed to ammonia the Ag hyperfine splitting of silver tetramer decre ases from 13.9 to 10.7 mT proving that Ag-4(3+) clusters are located in the sites accessible to adsorbates.