Class B Sodalites: Nonstoichiometric Silver,Sodium Halosodalites

Nonstoichiometric silver,sodium bromosodalites of the compositions M_8-2nN_2nX_2-pOH_p-SOD and M_8-2nN_2nX_2-p[]_p-SOD have been synthesized, where. N = Ag⁺, Na⁺, X = Cl^-, Br^-, I^-, 2n = 0-8, p = 0-2, [] refers to anion-free cages ana SOD = (SiAlO₄)₆^6-. These materials allow one to control the filling of both Ag⁺ and X^- ions in a sodalite host lattice in a systematic manner to fabricate Na_4-nAg_nX semiconductor-component clusters. Combined results from powder XRD, Rietveld refinement, ²³Na MAS and DOR NMR, and far-IR and mid-IR spectroscopy indicate that these sodalites form a solid solution of Na_3-mAg_m clusters in anion-free β-cages interspersed with Na_4-nAg_nX clusters. The clusters are statistically distributed throughout the lattice. However, silver ions are associated preferentially with cavities containing halide anions. The data also demonstrate that these materials offer the opportunity to manipulate the extent of collective electronic and vibrational interactions between monodispersed Na_4-nAg_nBr clusters in a perfectly crystalline host. The anion strongly mediates the vibrational coupling. The electronic coupling between clusters increases with Ag⁺ and X^- loading levels. Support for this idea comes from extended Hückel molecular orbital calculations. At low Ag⁺/X^- loadings, intrasodalite AgX resembles the gas-phase molecule (bond length, optical spectra). Optical absorption bands broaden and the absorption edge moves toward that of the bulk semiconductor at higher Ag⁺/X^- loadings.