SrTi(IO3)6·2H2O and SrSn(IO3)6: distinct arrangements of lone pair electrons leading to large birefringences

Three new iodates SrTi(IO3)6·2H2O, (H3O)2Ti(IO3)6, and SrSn(IO3)6 have been synthesized via a facile hydrothermal method. The three compounds have zero-dimensional crystal structures composed of one [MO6]8− (M = Ti, Sn) octahedron connected with six [IO3]− trigonal pyramids. However, the particular coordination of Sr2+ cations results in distinct arrangements of lone pair electrons in an [IO3]− trigonal pyramid, which leads to large birefringences. More importantly, this work enriches the species crystal chemistry for [M(IO3)6]2− (M = Ti, Sn) clusters-containing iodates.