Gradual evolution of hydrogen-bonding patterns with the carbamoylcyanonitrosomethanide anion in a series of aliphatic diammonium salts

Developing the structures of organic materials that rely on the hydrogen bonding of multifunctional substrates is often complicated due to a competition between various possible motifs. In this context, the illustrative case of the carbamoylcyanonitrosomethanide anion, ONC(CN)–C(O)NH₂]^?, suggests sufficient control over the crystal lattice with a set of supramolecular synthons, which are specific to all the present nitroso, carbamoyl and cyano groups. The structures of the carbamoylcyanonitrosomethanide salts of ethane-1,2-diammonium, C₂H₁₀N₂²⁺·2C₃H₂N₃O₂^?, (1), piperazine-1,4-diium, C₄H₁₂N₂²⁺·2C₃H₂N₃O₂^?, (2), butane-1,4-diammonium, C₄H₁₄N₂²⁺·2C₃H₂N₃O₂^?, (3), and hexane-1,6-diammonium, C₆H₁₈N₂²⁺·2C₃H₂N₃O₂^?, (4), reveal two- and three-dimensional hydrogen-bonded frameworks governed by a set of site-selective interactions. The strongest N—H…O hydrogen bonds N…O = 2.6842 (17)–2.8718 (17) Å, mean 2.776 (2) Å] are associated with the polarized ammonium N—H donors and nitroso O-atom acceptors, which sustain invariant motifs in the form of nitroso/ammonium dimers. Subtle structural changes within this series of compounds concern the rupture of some weaker interactions, i.e. mutual hydrogen bonds of the carbamoyl groups in (1)–(3) N…O = 2.910 (2)–2.9909 (18) Å; mean 2.950 (2) Å] and carbamoyl/nitrile hydrogen bonds in (1), (2) and (4) N…N = 2.936 (2)–3.003 (3) Å, mean 2.977 (2) Å], providing a gradual evolution of the hydrogen-bonding pattern. A hierarchy of the synthons involving three different groups could be applicable to supramolecular synthesis with polyfunctional methanide species, suggesting also a degree of control over layered and interpenetrated hydrogen-bonded networks.