In my master's thesis, I determined the crystal structure of eight hybrid organic-inorganic morpholinium compounds using X-ray diffraction on a single crystal. These include two iodidoplumbates labeled Pb(1) and Pb(2) with the formulas (C$_4$H$_{10}$NO)$_2$PbI$_4$ and (C$_4$H$_{10}$NO)PbI$_3$, three iodidobismuthates labeled Bi(1), Bi(2), and Bi(3) with the formulas (C$_4$H$_{10}$NO)$_2$(H$_3$O)BiI$_6$·H$_2$O, (C$_4$H$_{10}$NO)$_4$Bi$_4$I$_{16}$·6H$_2$O and (C$_4$H$_{10}$NO)$_4$(BiI$_6$)(I$_3$), as well as three iodidoantimonates labeled Sb(1), Sb(2), and Sb(3) with the formulas (C$_4$H$_{10}$NO)$_2$SbI$_5$, (C$_4$H$_{10}$NO)$_4$Sb$_4$I$_{16}$·2(CH$_3$CN) and (C$_4$H$_{10}$NO)$_4$(I$_3$)SbI$_6$. No structure or compound of any morpholinium iodidobismuthate or iodidoantimonate has been described in the literature to date.
The discussed compounds have in common that the morpholinium cation occurs in a chair conformation and is connected to the inorganic part of the structure via hydrogen N–H···I bonds, van der Waals interactions, and also ionic bonds, thus classifying the compounds as structural hybrids or hybrid materials of type II. Common to the inorganic part of the structures is that the central ion (Pb$^{2+}$, Bi$^{3+}$ or Sb$^{3+}$) is surrounded by six iodido ligands in the form of a distorted octahedron. Bi(3) and Sb(3) are isostructural, and both of them include an additional triiodide anion besides the mononuclear coordination anion (BiI$_6^{3−}$ or SbI$_6^{3−}$). The Bi(1) structure also contains the same mononuclear anion besides oxonium ions and water molecules. Bi(2) and Sb(2) contain centrosymmetric tetranuclear Bi$_4$I$_{16}^{4–}$ or Sb$_4$I$_{16}^{4–}$, in which the octahedra are connected via shared edges, and solvent molecules, which are water in the case of Bi(2) and acetonitrile in the case of Sb(2). The anions in Sb(1) and Pb(2) are 1D infinite chains. In Sb(1), the octahedra are linked into chains via shared vertices and in Pb(2) via shared faces. In Pb(1), the octahedra are connected via vertices into 2D infinite layers. Despite the diversity of the structures I have determined, there is none among them where the octahedra are connected via all vertices into a 3D infinite anion, so they are not hybrid perovskites in the basic sense of the term perovskite.
The compounds were also characterized by X-ray powder diffraction, elemental CHN analysis, and thermal analysis. In all compounds, the organic part of the hybrid structure decomposes in the interval between 190 to 270 °C. During the thermal decomposition, a significant amount of lead, bismuth, and antimony is released from the compounds.
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