The three metal iodates Ba(MoO2)(2)(IO3)(4)O (1), Ba-3 [(MoO2)(2)(IO3)(4)O(OH)(4)]center dot 2H(2)O (2), and Sr-[(MoO2)(6)(IO4)(2)O-4]center dot H2O (3) have been successfully synthesized by introducing second-order Jahn-Teller distorted Mo6+ cations by a mild hydrothermal method. Single-crystal X-ray diffraction (XRD) was used to determine the structures of the three title compounds. In compound 1, the [Mo2O11 ](10-) dimers connect with the [IO3](-) units by sharing oxygen atoms to form two-dimensional (2D) layers that are separated by the Ba2+ cations. For comparison, the [Mo2O11](10-) dimers and the [IO3](-) units are isolated in compound 2, and they are connected by the [BaO11](20-) polyhedra forming a 3D network. For compound 3, the [MoO6](6-) polyhedra link with each other by corner and edge sharing to build 2D corrugated layers with tunnels containing isolated [IO4](3-) units. The [SrO9](16-) polyhedra link the 2D corrugated layers to form a 3D network. The infrared (IR) spectra, the ultraviolet-visible- near-infrared (UV-vis-NIR) diffuse reflectance spectra, and thermal stabilities of compounds 1 and 2 are presented. In addition, the theoretical calculations are also carried out to evaluate their band gaps and density of states.