Sr3Bi2(SeO3)6·H2O: A novel anionic layer consisting of second-order Jahn–Teller (SOJT) distortive cations

Exploration of New Birefringent Crystals in Bismuth d0 Transition Metal Selenites

“…The peaks in 400-570 cm À1 can be assigned to the BiÀO/F vibrations and the bonds associated with the SeÀOv ibrations appeared at 500-800 cm À1 .T hese assignments are in good agreement with the literature. [19] UV/Vis-NIR absorption spectra analyses of the compounds 1-5 have been obtainedi nt he wavelength range of 2500-200 nm at room temperature. Optical diffuse reflectance studies show that all compounds are almost transparent in the range of 2500-500 nm, with an optical band gap of approximately 3.58, 3.76, 3.24,3.30, and 4.09 eV respectively (FigureS9), which is comparable to reported works.…”

Diverse Lanthanide Coordination and Selective Ion Exchange in the Microporous Selenites Na4Ln4(SeO3)7O·nH2O (Ln = Gd, Tb, Dy, Ho, Er, Tm, and Yb)

“…First, the Ln 3+ cations tend to have high coordination numbers of eight or nine, and the subsequent geometric environments seldom allow for a center of symmetry. Second, oxoanions containing selenium in the +4 oxidation state are most typically found as the selenite anion, SeO 3 2– , and a second-order Jahn–Teller (SOJT) distortion leads to stereochemical-activity of the lone pair of electrons and formation of a trigonal pyramidal geometry that is also prohibitive for inversion symmetry. − Thus, when these two building units are coupled together noncentrosymmetric structures can result. Examples of compounds that realize these structural features and corresponding symmetry-dependent properties include Nd 2 (V 2 O 4 )­(SeO 3 ) 4 ·H 2 O, Ln­(VO 2 )­(SeO 3 ) 2 (Ln = Eu, Gd, Tb), H 3 Ln 4 Mo 9.5 O 32 (SeO 3 ) 4 (H 2 O) 2 (Ln = La, Nd), and Ln 2 Mo 3 O 10 (SeO 3 ) 2 (H 2 O) (Ln = Eu, Dy, Er). − …”