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, (Pb2V2Se2O11)-Se-v (1), (Pb2V3Se5O18)-Se-IV (2), (Pb2Nb2Se4O15)-Se-V (3), (Bi2V2Se4O16)-Se-V (4), and (Bi2Mo2Se2O13)-Se-VI (5). The structure of 1 features a 3D network built by 10 anionic chains of [V2O5(SeO3)(2)](4-) interconnected by Pb2+ ions with six-membered-ring (MR) tunnels along the b axis. The structure of 2 features a 3D anionic framework composed of (VO6)-O-IV octahedra corner-sharing with SeO3 anions, with the Pb2+ ions located at the resultant 8-MR tunnels. The oxidation state of the vanadium cation is 4+ due to the partial oxidation of V2O3 by SeO2 at high temperature. The structure of 3 features novel 1D double chains of [Nb2O3(SeO3)(4)](4-) that are interconnected by Pb2+ 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(SeO3)(2)](2+) and 1D [(VO2)(2)(SeO3)(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 Mo2O10 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.