Crystal structure of bis-(3-carb-oxy-1-methyl-pyrid-inium) octa-bromide.

The crystal structure of the title salt, bis-(3-carb-oxy-1-methyl-pyridinium) octa-bromide, 2C 7 H 8 NO 2 + ·Br 8 2- , consists of 3-carb-oxy-1-methyl-pyridinium ( N -methyl-nicotinic acid) cations, which are stacked between relatively rare [Br 8 ] 2- anions. The polybromide [Br 8 ] 2- anion has point group symmetry and can be described as being composed of two [Br 3 ] - anions connected with a Br 2 mol-ecule in a Z -shaped manner. Contacts between neighboring octa-bromide anions ensure the creation of pseudo-polymeric chains propagating along [111]. The organic cations are located between anionic chains and are connected to each other through O-H⋯O hydrogen bonds and to the [Br 8 ] 2- anions through π⋯Br inter-actions that induce the creation of a supra-molecular tri-periodic network. In addition, the presence of weak C-H⋯Br contacts leads to the creation of layers, which align parallel to (11).