Synthesis and Structure of Large Optically Clear Crystals of Gallogermanate Sodalite

Large transparent crystals (up to 800 μm) of a hydroxy-sodium gallogermanate sodalite have been prepared at between 100 and 150 °C in aqueous sodium tetramethylammonium hydroxide solutions. Single-crystal structure analysis gave the expected space group (P4̄3n) but an unexpectedly small unit cell (8.951 Å) in which the longer (Ga,Ge)−O bond lengths are compensated by T−O−T bond angles of ∼110°. The crystals provide a readily made framework for structure studies of encapsulated chemical species.