Two intricate hydrogen-bonded networks formed by m-sulfophenylphosphonic acid, melamine, and water molecules

Cocrystallizations of melamine (ma) with m-sulfophenylphosphonic acid (sppH3) from water in different molar ratios (2:1 and 4:1) offer [(maH)2(sppH)]·3H2O (1) and [(maH)3(spp)(ma)]·12H2O (2), respectively. Structure analysis reveals that two very intricate hydrogen-bonded networks are formed in them, with two or three protons of the m-sulfophenylphosphonic acid being transferred to melamine. The resultant (sppH)2− or (sppH)3− anion can form as many as 12 or 14 hydrogen bonds with melamine and water molecules, showing a very high hydrogen-bonding capability.