Picolinamidium Squarate and Di-P Squarate Dihydrate

Abstract

The crystal structure determinations of picolinamidium squarate, C <inf>6</inf>H<inf>7</inf>N<inf>2</inf>O+.C<inf>4</inf>O <inf>4</inf>-, (I), and di-p-toluidinium squarate dihydrate, 2C <inf>7</inf>H<inf>10</inf>N+.C<inf>4</inf>O<inf>4</inf> 2-.2H<inf>2</inf>O, (II), are reported. While salt formation occurs by donation of one H atom from squaric acid to the picolinamide molecule in (I), in compound (II), each squaric acid molecule donates one H atom to the p-toluidine N atom of two trans p-toluidine molecules. In (I), the pyridine ring is coplanar with the squarate monoanion through imposed crystallographic mirror symmetry; in (II), the dihedral angle between the p-toluidine moiety and the squarate dianion is 70.71 (1)°. In (I), a three-dimensional structure is formed via van der Waals interactions between parallel planes of molecules, with hydrogen-bond interactions (N-H· · ·O and O-H· · ·O) acting within the planes; hydrogen bonds form a three-dimensional network in (II).