Supramolecular organization of organoammonium squarates

Abstract

Syntheses, thermal behavior, and IR data of three hydrogen squarates, Hsq(-), with 2-(acetylamino)-4-methylpyridinium, [(C8H11N2O)(HC4O4)] (1), 2-carboxamido-pyridinium, [(C6H7N2O)-(HC4O4)] (2), and 2-methylpyridinium cations, [(C6H8N)(HC4O4)(H2O)] (3), and one squarate, sq(2-), with 2-amino-4-methyl-pyrimidinium cations, [(C6H9N2)(2)(C4O4)] (4) are reported. The crystal structures of 1 and 4 have been studied. The compounds decompose in two thermal stages: (i) release of organic base, (ii) decomposition of squarate. Crystallographic analyses show that I and 4 have S6, R-2(2)(10) R-2(2)(9) R-2(2)(7) rings. The hydrogen bonding motifs formed by the hydrogensquarate anions interact with the ammonium cations through N-H center dot center dot center dot O hydrogen bonds and give rise to predominantly layered structures, which also exhibit three-dimensional connectivity.