Fig. 2: Organic interactions, and their influence on the inorganic backbone.

a Protonation of an amine to form ammonium, mechanical deformation to create a dimer-ready ligand, and dimer formation. Numbers indicate atomic Bader charges. The electron-density difference (EDD) plot show changes in electron density upon dimer formation from two monomers. The rendered yellow and cyan regions correspond to electron accumulation and depletion. Color code: nitrogen (blue), carbon (black), hydrogen (white), lead (gray), and iodine (purple); b electron accumulation (bond) between two ligands, associated with a cyclic dipole formation around the ring, shifting electrons to electrophilic regions close to the proton-like hydrogens. EDD isosurfaces correspond to smaller charge transfers, relative to (a, c), to better portray dipole formation. Bader volumes indicate charge sharing (covalency) and a small charge transfer from the nitrogen on one ligand to the hydrogen on the other; c formation of strong hydrogen bonds between the dimer and the axial iodides of the inorganic backbone. We observe no strong interactions between the ammonium group and an equatorial iodide.