Crystal structures and thermal behavior of complexes of group 13 metal halides with pyridine-type ligands

The Field of Main Group Lewis Acids and Lewis Superacids: Important Basics and Recent Developments

New developments in the field of Lewis acidity are highlighted, with the focus of novel Lewis acids and Lewis superacids of group 2, 13, 14, and 15 elements. Several important basics, illustrated by modern examples (classification of Donor-Acceptor (DA) complexes, amphoteric nature of any compound in terms of DA interactions, reorganization energies of main group Lewis acids and the role of the energies of frontier orbitals) are presented and discussed. It is emphasized that the Lewis acidity phenomena are general and play vital role in different areas of chemistry: from weak "atomophilic" interactions to the complexes of Lewis superacids.

Iodine-Chemisorption, Interpenetration and Polycatenation: Cationic MOFs and CPs from Group 13 Metal Halides and Di-Pyridyl-Linkers

Eight cationic, two-dimensional metal-organic frameworks (MOFs) were synthesized in reactions of the group 13 metal halides AlBr3 , AlI3 , GaBr3 , InBr3 and InI3 with the dipyridyl ligands 1,2-di(4-pyridyl)ethylene (bpe), 1,2-di(4-pyridyl)ethane (bpa) and 4,4'-bipyridine (bipy). Seven of them follow the general formula 2 ∞ [MX2 (L)2 ]A, M=Al, In, X=Br, I, A- =[MX4 ]- , I- , I3 - , L=bipy, bpa, bpe. Thereby, the porosity of the cationic frameworks can be utilized to take up the heavy molecule iodine in gas-phase chemisorption vital for the capture of iodine radioisotopes. This is achieved by switching between I- and the polyiodide I3 - in the cavities at room temperature, including single-crystal-to-single-crystal transformation. The MOFs are 2D networks that exhibit (4,4)-topology in general or (6,3)-topology for 2 ∞ [(GaBr2 )2 (bpa)5 ][GaBr4 ]2 ⋅bpa. The two-dimensional networks can either be arranged to an inclined interpenetration of the cationic two-dimensional networks, or to stacked networks without interpenetration. Interpenetration is accompanied by polycatenation. Due to the cationic character, the MOFs require the counter ions [MX4 ]- , I- or I3 - counter ions in their pores. Whereas the [MX4 ]- , ions are immobile, iodide allows for chemisorption. Furthermore, eight additional coordination polymers and complexes were identified and isolated that elaborate the reaction space of the herein reported syntheses.

Red emitting Sm(II) phosphors: thermally switchable luminescence in Sm(AlX4)2 (X = Cl, Br) by 5d-4f and intra-4f transitions

Divalent samarium compounds of the constitution Sm(AlX₄)₂, X = Cl, Br, show remarkable luminescence of Sm²⁺. At room temperature, the luminescence is dominated by parity-allowed broad-band 4f⁵5d¹ → 4f⁶ emission with additional ⁵D₀ → ⁷F_J narrow-line emission. At 79 K, only the intra-4f-emission is observed, rendering the mechanism thermally switchable. The luminescence processes and their temperature dependence were determined including lifetime investigations for both, room temperature and 79 K, as well as quantum efficiency determinations. In addition, a new pathway for the synthesis of Sm(AlCl₄)₂ and the previously unknown Sm(AlBr₄)₂ is reported.

Structures and Chemical Bonding in Antimony(III) Bromide Complexes with Pyridine

Weakly or "partially" bonded molecules are an important link between the chemical and van der Waals interactions. Molecular structures of six new SbBr₃ -Py complexes in the solid state have been determined by single-crystal X-ray diffraction analysis. In all complexes all Sb atoms adopt a pseudo-octahedral coordination geometry which is completed by additional Sb⋅⋅⋅Br contacts shorter than the sum of the van der Waals radii, with Br-Sb⋅⋅⋅Br angles close to 180°. To reveal the nature of Sb-Br and Sb-N interactions, the DFT calculations were performed followed by the analysis of the electrostatic potentials, the orbital interactions and the topological analysis. Based on Natural Bond Orbital (NBO) analysis, the Sb-Br interactions range from the covalent bonds to the pnictogen bonds. A simple structural parameter, non-covalence criterion (NCC) is defined as a ratio of the atom-atom distance to the linear combination of sums of covalent and van der Waals radii. NCC correlates with E(2) values for Sb-N, Sb-Cl and Sb-Br bonds, and appears to be useful criterion for a preliminary evaluation of the bonding situation.

Structural variety of aluminium and gallium coordination polymers based on bis-pyridylethylene: from molecular complexes to ionic networks

Diverse molecular (0D and 1D) as well as ionic (0D, 1D, 2D, mixed 1D–2D) crystal structures of complexes of aluminium and gallium trihalides with bis(4-pyridylethylene) were obtained by solvent-free melt reactions.