Twisted Imide Bond in Noncyclic Imides. Synthesis and Structural and Vibrational Properties of <i>N</i>,<i>N</i>-Bis(furan-2-carbonyl)-4-chloroaniline

Abstract

A novel imide compound (C₁₆H₁₀ClNO₄) was synthesized in a single step by the reaction of 2-furoic acid with 4-chloroaniline in a 2:1 molar ratio using carbonyldiimidazole (CDI) in dry THF. The structure was supported by spectroscopic and elemental analyses and the single-crystal X-ray diffraction data. Crystallographic studies revealed that the compound crystallized in a monoclinic system with space group <i>P</i>2₁/<i>c</i> and unit cell dimensions <i>a</i> = 12.2575(5) Å, <i>b</i> = 7.7596(2) Å, <i>c</i> = 15.0234(7) Å, α = γ = 90°, β = 92.771(4)°, <i>V</i> = 1427.25(10) ų, <i>Z</i> = 4. The imide bond is twisted, and the OC–N–C­(O) units deviate significantly from planarity with dihedral angles around the imide group reaching ca. −150.3° (C1–N1–C2–O21 = −148.8° and C2–N1–C1–O11 = −151.9°). The nonplanarity of the imide moiety and the related conformational properties are discussed in a combined approach that includes the analysis of the vibrational spectra together with theoretical calculation methods, especially in terms of natural bond orbital (NBO) calculations