A long symmetric N•••H•••N hydrogen bond in bis(4-aminopyridinium)(1+) azide(1-): redetermination from the original data

The structure of the title molecular salt, C10H13N4+center dot N-3(-), has been redetermined from the data published by Qian & Huang [Acta Cryst. (2010), E66, o3086; refcode WACMIY (Groom et al., 2016)]. The improvement of the present redetermination consists in a correction of the site-occupancy parameter of the bridging H atom between the pyridine rings, as well as of its position. The present study has shown that the bridging H atom (site symmetry 2) is involved in a symmetric N center dot center dot center dot H center dot center dot center dot N hydrogen bond, which is one of the longest ever observed [N center dot center dot center dot N = 2.678 (3) angstrom]. In addition, there are also present weaker N-am-H center dot center dot center dot N-az hydrogen bonds (am = amine and az = azide) of moderate strength and pi-electron pyridine center dot center dot center dot pi-electron interactions in the structure. All the azide N atoms also lie on a twofold axis.