Supramolecular hydrogen-bonded structures between melamine and N-heterocycles

Melamine (M) forms hydrogen bonded adducts with the N-heterocycles tris(2-pyridyl)-triazine (TPTZ) and tetrakis(4-N-methylpyridinumyl)porphyrin tetratosylate (TMPyP-Tos). The 4:3 adduct 4M center dot 3TPTZ was obtained under solvent-free conditions and the 3:1 adduct 3M center dot TMPyP-Tos center dot 9H(2)O in aqueous solution. In both adduct phases N-heterocycles are arranged in pi-pi stacks and melamine molecules are arranged perpendicular to these stacks. Whereas cohesion between the extended pi-systems of N-heterocycles is mainly achieved by dispersive interactions no stacking interactions between melamine molecules occur. Melamine units are orientated in such a way to be located most suitable as donors and acceptors, respectively. for a dense hydrogen bonding network. In 4M center dot 3TPTZ all molecules are involved in hydrogen bonding, whereas in 3M center dot TMPyP-Tos center dot 9H(2)O hydrogen bridges are primarily formed between melamine, tosylate and water units and the macrocycle TMPyP is mainly bound by electrostatic interactions. (C) 2012 Elsevier B.V. All rights reserved.