Experimental

R factor = 0.036; wR factor = 0.092; data-to-parameter ratio = 13.4. In the title salt, C16H21N4 +ClO40.5C4H4O4, fumaric acid molecules, situated across crystallographic inversion centres, are O—H N hydrogen bonded to two protonated 1,4-bis(4-pyridylmethyl)piperazine cations, forming trimolecular units. These construct one-dimensional supramolecular ribbons by N—H N hydrogen bonding, and further aggregate via – interactions [shortest C C contact = 3.640 (1) Å] and perchlorate-mediated C—H O interactions. Related literature For the preparation of bis(4-pyridylmethyl)piperazine, see: Pocic et al. (2005). For a cadmium fumarate coordination polymer containing bis(4-pyridylmethyl)piperazine, see: Martin et al. (2009).