Hydrogen bond patterns in aromatic and aliphatic dioximes

Abstract

Despite their established hydrogen bonding capability, oxime functional groups (–C(R′)NOH) have received far less attention in supramolecular chemistry than their carboxyl and amide counterparts. Here we report a series of dioximes (R′H, CH₃, NH₂) for which hydrogen bonding patterns have been examined in the solid state to establish the reliability of hydrogen-bonded synthons available for use in supramolecular syntheses using oximes. In all cases, network structures were formed, most frequently propagated through oxime–oxime O–H⋯N hydrogen-bonded dimer formation [R²₂(6) graph set] and less often using C(3) chain or R⁴₄(12) ring arrangements. Even in the systems where R′ = NH₂, robust and dominant oxime–oxime hydrogen bonding prevails, with amino groups playing a supporting role in network construction primarily via weaker N–H⋯O hydrogen bonds. The compounds studied are aromatic dioximes 1,3-C₆H₄(C(R′)NOH)₂1–3 and 1,4-C₆H₄(C(R′)NOH)₂4–6 (R′ = H, CH₃, NH₂), and aliphatic dioximes fumaramide dioxime 7 (R′ = NH₂) and succinamide dioxime 8 (R′ = NH₂).