Tatiana A. Shestimerova

From Isolated Anions to Polymer Structures through Linking with I2: Synthesis, Structure, and Properties of Two Complex Bismuth(III) Iodine Iodides

We report the synthesis, crystal structures, and optical properties of two new compounds, K18Bi8I42(I2)0.5·14H2O (1) and (NH4)7Bi3I16(I2)0.5·4.5H2O (2), as well as the electronic structure of the latter. They crystallize in tetragonal space group P4/ mmm with the unit cell parameters a = 12.974(1) and c = 20.821(3) Å for 1 and a = 13.061(3) and c = 15.162(7) Å for 2. Though 1 and 2 are not isomorphous, their crystal structures display the same structural organization; namely, the BiI6 octahedra are linked by I2 units to form disordered layers in 1 and perfectly ordered chains in 2. The I-I bond distances in the thus formed I-I-I-I linear links are not uniform; the central bond is only slightly longer than in a standalone I2 molecule, whereas the peripheral bonds are significantly shorter than longer bonds typical for various polyiodides, which is confirmed by Raman spectroscopy. The analysis of the electronic structure shows that the atoms forming the I-I-I-I subunits transfer electron density from their occupied 5p orbitals onto their vacant states as well as onto 6s orbitals of bismuth atoms that center the BiI6 octahedra. This leads to low direct band gaps that were found to be 1.57 and 1.27 eV for 1 and 2, respectively, by optical absorption spectroscopy. Luminescent radiative relaxation was observed in the near-IR region with emission maxima of 1.39 and 1.24 eV for 1 and 2, respectively, in good agreement with the band structure, despite the strong quenching propensity of I2 moieties.

Synthesis and crystal structure of new double mercury silver phosphide iodide Hg12Ag41P88I41

New double mercury silver phosphide iodide Hg12Ag41P88I41 (1) was synthesized and its crystal structure was established. Compound 1 crystallizes in the cubic system. The characteristic feature of the crystal structure 1 is the presence of the anionic cage clusters P113−, which have been previously found in alkali metal compounds only. The well-ordered P113− clusters form a system of polyhedra, which encapsulate various disordered α-AgI-type fragments.

Synthesis, structure, and properties of LnBiI 6 •13H 2 O (Ln = La, Nd)

Two new iodobismuthates with the composition LnBiI6•13H2O (Ln = La, Nd) were synthesized and their crystal structures were determined. The compound LaBiI6•13H2O crystalizes in the orthorhombic space group Pna21, a = 24.206(5), b = 8.405(1), c = 26.360(5) Å; the compound NdBiI6•13H2O crystalizes in the monoclinic space group P21/n, a = 14.553(3), b = 13.386(3), c = 27.541(6) Å, β = 92.80(3)°. In both crystal structures, the cations Ln(H2O)93+ and the anions BiI63– alternate, forming a NaCl-type structure, and the structures themselves differ in the arrangement of water of crystallization that leads to the formation of dissimilar systems of hydrogen bonds. Both compounds undergo decomposition when heated, which is accompanied first by a partial liberation of water molecule, followed by pyrohydrolysis to form oxoiodides LnOI as final solid products. According to optical measurements, the band gap of the obtained compounds was equal to 1.78 (La) and 1.71 (Nd) eV.