SrTi(IO 3 ) 6 ·2H 2 O and SrSn(IO 3 ) 6 : distinct arrangements of lone pair electrons leading to large birefringences.

Three new iodates SrTi(IO 3 ) 6 ·2H 2 O, (H 3 O) 2 Ti(IO 3 ) 6 , and SrSn(IO 3 ) 6 have been synthesized via a facile hydrothermal method. The three compounds have zero-dimensional crystal structures composed of one [MO 6 ] 8- (M = Ti, Sn) octahedron connected with six [IO 3 ] - trigonal pyramids. However, the particular coordination of Sr 2+ cations results in distinct arrangements of lone pair electrons in an [IO 3 ] - trigonal pyramid, which leads to large birefringences. More importantly, this work enriches the species crystal chemistry for [M(IO 3 ) 6 ] 2- (M = Ti, Sn) clusters-containing iodates.