From monomers to polymers: steric and supramolecular effects on dimensionality of coordination architectures of heteroleptic mercury( ii ) halogenide–tetradentate Schiff base complexes

In this study, neutral mercury( ii ) complexes of the composition [Hg( L1 )(μ-Cl) 2 Hg 3 Cl 6 ] n ( 1 ), [Hg( L1 )(μ-Br) 2 HgBr 2 ] ( 2 ), [Hg( L3 )Br 2 ] ( 2a ), [Hg( L1 )I 2 ] ( 3 ), [Hg( L2 )Cl 2 ]·CH 3 OH ( 4 ) and [Hg( L2 )(μ-Br)HgBr 3 ] 2 ( 5 ) ( L1 = benzilbis((pyridin-2-yl)methylidenehydrazone); L2 = benzilbis((acetylpyridin-2-yl)methylidenehydrazone)) are described. Single-crystal X-ray crystallography showed that the molecular complexes can aggregate into larger entities depending upon the anion coordinated to the metal centre. Iodide gives discrete monomeric complexes, bromide generates a 1D coordination polymer formed through Hg–Br–Hg bridges and chloride gives rise to an inorganic–organic hybrid material. The significant differences in the reaction conditions indicate that the anions exert a substantial influence on the formation of the compounds – smaller anions show a larger potential for bridging metal ions and forming coordination polymers. A minute increase in the bulkiness of the ligand (two extra methyl substituents in L2 ) dramatically changes the coordination architectures, and leads to the formation of monomeric (chloride and iodide) and oligomeric (bromide) structures, rather than polymeric structures. The noncovalent C–H/π and π-hole interactions observed in the solid state architecture of some complexes have been rationalized by means of theoretical DFT calculations.