Polybromides of pyridinium and quinolinium-type cations: Cation-induced structural diversity and theoretical analysis of Br⋯Br interactions

Abstract

Four novel polybromide salts containing pyridinium-type and quinolinium-type cations – {(2-Br-5-MePy)2H}Br3 (1), (1,3,5-MePy){(Br3) (Br2)} (2), (1-Et-2,6-MePy){(Br3) (Br2)0.5} (3) and (N-MeIsoquin){(Br3) (Br2)0.5} (4) were isolated from HBr/Br2 solutions. Hirshfeld surface analysis for the organic parts of X-ray structures of 1–4 and a set of related compounds reported earlier reveals that in all cases crystal packing is determined primarily by intermolecular contacts BrH, HH, С–H, BrBr, and BrC. DFT calculations allowed estimation of Br⋯Br halogen bonding energies (0.9–7.5 kcal/mol).