Supramolecular hydrogen-bonded structure of a 1:2 adduct of melamine with boric acid

Boric acid (B) forms a 2:1 hydrogen-bond adduct, M·2B, with melamine (M), wherein, a finite tetrameric ribbon of boric acid forms hydrogen bonds with the nitrogen donor sites of M. Hydrogen-bonded layers of B and M in the bc-plane are connected by boric acid units along the a-axis to give a three dimensional structure. Interestingly, one of the amino groups of M does not participate in hydrogen bonding unlike all the hydroxyl groups of B.