Supramolecular Loop-Chain Network of Pillared Layers via 4,4‘-Bipyridine

A new structural motif occurs in the organic salt of formula {[H3bta]2[H2-4,4‘-bpy]} 1 where stacks of
infinite pillared rhombically distorted square grid networks are interpenetrated by the same pillared networks in
a loop−chain modus. Interestingly, the X-ray structure of 1 reveals two [H3bta]- monoanions of piromellitic acid
(benzene-1,2,4,5-tetracarboxylic acid, H4bta) and one [H2-4,4‘-bpy]2+ cation in the asymmetric unit. Each H3bta-
unit builds up two different hydrogen-bonded sheets (A and B) which are parallel to the ab-plane. The [H2-4,4‘-bpy]2+ cation acts as a pillar along the c-axis linking nonadjacent A and B sheets to afford an extended three-dimensional network.