Crystal structures and Hirshfeld surface analyses of N, N-di-methyl-acetamide-1-(dimethyl-λ4-aza-nyl-idene)ethan-1-ol tribromide (1/1), N, N-di-methyl-acetamide-1-(dimethyl-λ4-aza-nyl-idene)ethan-1-ol di-bromido-iodate (1/1) and N, N-di-methyl-acetamide-1-(dimethyl-λ4-aza-nyl-idene)ethan-1-ol di-chlorido-iodate (1/1)

Abstract

In the title compounds, N,N-di-methyl-acetamide-1-(dimethyl-λ⁴-aza-nyl-idene)ethan-1-ol tribromide (1/1), C₄H₉NO·C₄H₁₀NO⁺·Br₃ ^- or [(C₄H₉NO)·(C₄H₁₀NO)](Br₃), (I), N,N-di-methyl-acetamide-1-(dimethyl-λ⁴-aza-nyl-idene)ethan-1-ol di-bromido-iodate (1/1), C₄H₉NO·C₄H₁₀NO⁺·Br₂I^- or [(C₄H₉NO)·(C₄H₁₀NO)](Br₂I), (II), and N,N-di-methyl-acetamide-1-(dimethyl-λ⁴-aza-nyl-idene)ethan-1-ol di-chlorido-iodate (1/1), C₄H₉NO·C₄H₁₀NO⁺·Cl₂I^- or [(C₄H₉NO)·(C₄H₁₀NO)]·(Cl₂I), (III), all the anions are almost linear in geometry and all the cations, except for the methyl H atoms, are essentially planar. In the crystal structure of (I), the cations are linked by pairs of C-H⋯O hydrogen bonds, forming inversion dimers with an R ₂ ²(8) ring motif. These dimers also exhibit O-H⋯O hydrogen bonding. Dimerized cation pairs and anions are arranged in columns along the a axis. In the crystal of (II), the cations are linked by pairs of O-H⋯O and C-H⋯O hydrogen bonds, forming an R ₄ ⁴(14) ring motif. These groups of cations and the anions form individual columns along the a axis and jointly reside in planes roughly parallel to (011). In the crystal of (III), cations and anions also form columns parallel to the a axis, resulting in layers parallel to the (020) plane. Furthermore, the crystal structures of (I), (II) and (III) are consolidated by strong halogen (Br and/or I and/or Cl)⋯H and weak van der Waals inter-actions. In addition to the structural evaluation, a Hirshfeld surface analysis was carried out.

Keywords: Hirshfeld surface analysis; crystal structure; di­methyl­acetamide; hydrogen bond; trihalide.