Structural comparisons between methylated and unmethylated nitrophenyl lophines

The lophine derivative 2‐(2‐nitrophenyl)‐4,5‐diphenyl‐1H‐imidazole, C₂₁H₁₅N₃O₂, (I), crystallized from ethanol as a solvent‐free crystal and from acetonitrile as the monosolvate, C₂₁H₁₅N₃O₂·C₂H₃N, (II). Crystallization of 2‐(4‐nitrophenyl)‐4,5‐diphenyl‐1H‐imidazole from methanol yielded the methanol monosolvate, C₂₁H₁₅N₃O₂·CH₄O, (III). Three lophine derivatives of methylated imidazole, namely, 1‐methyl‐2‐(2‐nitrophenyl)‐4,5‐diphenyl‐1H‐imidazole methanol solvate, C₂₂H₁₇N₃O₂·CH₄O, (IV), 1‐methyl‐2‐(3‐nitrophenyl)‐4,5‐diphenyl‐1H‐imidazole, C₂₂H₁₇N₃O₂, (V), and 1‐methyl‐2‐(4‐nitrophenyl)‐4,5‐diphenyl‐1H‐imidazole, C₂₂H₁₇N₃O₂, (VI), were recrystallized from methanol, acetonitrile and ethanol, respectively, but only (IV) produced a solvate. Compounds (III) and (IV) each crystallize with two independent molecules in the asymmetric unit. Five imidazole molecules in the six crystals differ in their molecular conformations by rotation of the aromatic rings with respect to the central imidazole ring. In the absence of a methyl group on the imidazole compounds (I)–(III)], the rotation angles are not strongly affected by the position of the nitro group 44.8 (2) and 45.5 (1)° in (I) and (II), respectively, and 15.7 (2) and 31.5 (1)° in the two molecules of (III)]. However, the rotation angle is strongly affected by the presence of a methyl group on the imidazole compounds (IV)–(VI)], and the position of the nitro group (ortho, meta or para) on a neighbouring benzene ring; values of the rotation angle range from 26.0 (1) in (VI)] to 85.2 (1)° in (IV)]. This group repulsion also affects the outer N—C—N bond angle. The packing of the molecules in (I), (II) and (III) is determined by hydrogen bonding. In (I) and (II), molecules form extended chains through N—H...N hydrogen bonds with an N...N distance of 2.944 (5) Å in (I) and 2.920 (3) Å in (II)], while in (III) the chain is formed with a methanol solvent molecule as the mediator between two imidazole rings, with O...N distances of 2.788 (4)–2.819 (4) Å. In the absence of the imidazole N—H H‐atom donor, the packing of molecules (IV)–(VI) is determined by weaker intermolecular interactions. The methanol solvent molecule in (IV) is hydrogen bonded to imidazole O...N = 2.823 (4) Å] but has no effect on the packing of molecules in the unit cell.