Crystal structure of M(IO3)2 metal iodates, twinned bypseudo-merohedry, with MII: MgII, MnII, CoII, NiII and ZnII

Abstract The non-centrosymmetric materials Zn(IO 3 ) 2 , Mn(IO 3 ) 2 , Co(IO 3 ) 2 , Mg(IO 3 ) 2 and β-Ni(IO 3 ) 2 have been synthesised by evaporation of nitric acid solutions of metal salts and lithium iodate. All these compounds are isostructural and their structures were characterised both by X-ray diffraction on powder and single crystals. They crystallise in the monoclinic crystal system, space-group type P 2 1 (no. 4) with a pseudo-hexagonal lattice, as shown by the lattice parameters of Mn(IO 3 ) 2 for example: a = 11.247(1) Å, b = 5.045(1) Å, c = 11.246(1) Å, β = 120.02(1)°, V = 552.5(1) Å 3 , Z = 4. This monoclinic symmetry with a ∼ c and β ∼ 120° leads to a three-individual pseudo-hexagonal twin by pseudo-merohedry. The structure reveals a three-dimensional network in which each octahedrally coordinated cation is linked to ten others via iodate bridges. All these metal iodates generate second harmonics.