Influence of Aromatic Cations on the Structural Arrangement of Hg(II) Halides

Understanding
the structure and arrangement of hybrid metal halides
and their contribution to the optoelectronic properties is, thus far,
a challenging topic. In particular, new materials composed of d10 metal halides and pyridinium cations are still largely unexplored.
Therefore, we report the synthesis and characterization of six Hg­(II)
salts built up from (Hg2Cl6)2– or (HgX4)2– anions (X = Cl, Br, I)
and 2,2′-bipyridium (2,2′-Hbipy)+, 2,2′-bipyridine-1,1′-diium
(2,2′-H2bipy)2+, or 1,10-phenantrolinium
(1,10-Hphen)+ cations, using the same experimental conditions.
All of them have been characterized by PXRD, EA, FTIR-ATR, and 1H NMR spectroscopies; single-crystal X-ray diffraction; and
TG/DTA determinations. The study of their packing via Hirshfeld surface
analysis and 3D deformation density mapping revealed the contributions
of the intermolecular interactions to the structural arrangement,
notably, the effect of the cation planarity on them. Successively,
periodic DFT calculations showed that (i) the valence and conducting
bands are mainly composed of the p orbitals of the halide and the
organic cation, respectively, and (ii) the corresponding band gap
depends mainly on the halide.