When solvent becomes reactant: a study of 6-aminothiocytosine derivatives

The dissolution of 6-aminothiocytosine in common solvents (such as methanol, dimethyl sulfoxide and dichloromethane) under alkaline conditions is shown to afford new compounds with a 6-aminothiocytosine skeleton: 2,2'-disulfanediylbis(pyrimidine-4,6-diamine) (1), C₈H₁₀N₈S₂, 2,2'-[methanediylbis(sulfanediyl)]bis(pyrimidine-4,6-diamine) (2), C₉H₁₂N₈S₂, 2-[(methoxymethyl)sulfanyl]pyrimidine-4,6-diamine (3), C₆H₁₀N₄OS, and poly[(μ-4,6-diaminopyrimidine-2-sulfinato)potassium(I)] (4), [K(C₄H₅N₄O₂S)]_n. The crystal architectures of these compounds are found to be strongly influenced by extensive hydrogen-bond networks, although some individual features are also observed. Specifically, 1 is characterized by very short C-H...N hydrogen bonds, 2 features apparently weak and long C-H...π, C-H...S and π-π contacts as the greatest contributors to stabilization energy, while 3 contains ribbons of molecules formed by centrosymmetric dimers of two types, and 4 is characterized by layers with principal structural units comprising distorted six-molecule rings. The intermolecular interactions in 1-4 are characterized in terms of their geometry, topology and energy, and the corresponding results are confirmed and visualized using Hirshfeld surface analysis.