No abstract

The structure of the title compound, C8H9N3, a potential anti­tumour drug, was determined in order to give more insight into its structure–function relationships. The benzimidazole core of the mol­ecule was found to be exactly planar, while the substituents are displaced slightly from the mol­ecular plane [C—C—N—C and C—C—C—N torsion angles of 0.8 (3) and 179.0 (1)° for the methyl and amino groups, respectively]. The bond lengths are analysed in detail and compared with those of the parent unsubstituted analogues. The results show that the lone-pair electrons on the amino N atom are involved in conjugation with the adjacent π system and hence affect the charge distribution in the heterocycle. Two inter­molecular N—H⋯N and C—H⋯N hydrogen bonds have been identified.

Molecules of the title compound, C11H10N2O, are effectively planar. In the crystal structure, they are stabilized primarily by electrostatic interactions, as the dipole moment of the molecule is 4.56 D. In addition, the molecules are linked by weak C-H...N and C-H...O hydrogen bonds. An analysis of bonding conditions in the molecule was carried out using natural bond orbital (NBO) formalism.

The title compound, C8H4F4N2O4, crystallizes on a site of crystallographic inversion symmetry.

The 13C [hexadeutero‐dimethylsulfoxide (DMSO‐d6), hexamethyl‐phosphoramide (HMPA)‐d18and solid‐state] and 15N (solid‐state) NMR spectra of six C‐aminobenzimidazoles have been recorded. The tautomerism of 4(7)‐aminobenzimidazoles and 5(6)‐aminobenzimidazoles has been determined and compared with B3LYP/6‐311 + + G(d,p) calculations confirming the clear predominance of the 4‐amino tautomer and the slight preference for the 6‐amino tautomer. GIAO‐calculated absolute shieldings compare well with experimental chemical shifts. Copyright © 2008 John Wiley & Sons, Ltd.