4,4'-Methylenediphenol-4,4'-bipyridine (2/3): decarboxylation of 5,5'-methylenedisalicylic acid under hydrothermal conditions.

Reaction of 5,5'-methylenedisalicylic acid (5,5'-H(4)mdsa) with 4,4'-bipyridine (4,4'-bipy) and manganese(II) acetate under hydrothermal conditions led to the unexpected 2:3 binary cocrystal 4,4'-methylenediphenol-4,4'-bipyridine (2/3), C(13)H(12)O(2).1.5C(10)H(8)N(2) or (4,4'-H(2)dhdp)(4,4'-bipy)(1.5), which is formed with a concomitant decarboxylation. The asymmetric unit contains one and a half 4,4'-bipy molecules, one of which straddles a centre of inversion, and one 4,4'-H(2)dhdp molecule. O-H...N interactions between the hydroxy and pyridyl groups lead to a discrete ribbon motif with an unusual 2:3 stoichiometric ratio of strong hydrogen-bonding donors and acceptors. One of the pyridyl N-atom donors is not involved in hydrogen-bond formation. Additional weak C-H...O interactions between 4,4'-bipy and 4,4'-H(2)dhdp molecules complete a two-dimensional bilayer supramolecular structure.