Picolinamidium squarate and di-p-toluidinium squarate dihydrate

Abstract

The crystal structure determinations of picolinamidium squarate, C6H7N2O+.C4O4-, (I), and di-p-toluidinium squarate dihydrate, 2C(7)H(10)N(+).C4O4 (2-).2H(2)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)degrees. 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).