A series of new phases containing three different asymmetric building units

Systematic explorations of the new phases in the Pb(II)/Bi(III)-TM(d(0)/d(1))-Se(IV)-O systems by hydrothermal syntheses led to five new quaternary phases whose structures are composed of three different asymmetric building units, namely, Pb(2)V(V)(2)Se(2)O(11) (1), Pb(2)V(IV)(3)Se(5)O(18) (2), Pb(2)Nb(V)(2)Se(4)O(15) (3), Bi(2)V(V)(2)Se(4)O(16) (4), and Bi(2)Mo(VI)(2)Se(2)O(13) (5). The structure of 1 features a 3D network built by 1D anionic chains of [V(2)O(5)(SeO(3))(2)](4-) interconnected by Pb(2+) ions with six-membered-ring (MR) tunnels along the b axis. The structure of 2 features a 3D anionic framework composed of V(IV)O(6) octahedra corner-sharing with SeO(3) anions, with the Pb(2+) ions located at the resultant 8-MR tunnels. The oxidation state of the vanadium cation is 4+ due to the partial oxidation of V(2)O(3) by SeO(2) at high temperature. The structure of 3 features novel 1D double chains of [Nb(2)O(3)(SeO(3))(4)](4-) that are interconnected by Pb(2+) ions, forming a 3D network with 12-MR tunnels along the c axis. 4 features a 3D framework composed of 2D layers of [Bi(2)(SeO(3))(2)](2+) and 1D [(VO(2))(2)(SeO(3))(2)](2-) double chains. The structure of 5 features a 3D network composed of bismuth(III) selenite with large 10-MR tunnels along the a axis that are occupied by Mo(2)O(10) dimers. The results of optical diffuse-reflectance spectrum measurements and electronic structure calculations based on density functional theory methods indicate that all five compounds are wide-band-gap semiconductors. Luminescent property measurements for compounds 1-5 and magnetic measurements for compound 2 were also made.