Buy article online - an online subscription or single-article purchase is required to access this article.
organic compounds
The crystal and molecular structure of the title compound, C12H9N2+.Cl−.2C12H8N2, has been determined at 143 K. It consists of three phenanthroline units and one Cl− ion. One of the phenanthroline molecules is protonated at an N atom. In agreement with other authors, the protonated phenanthroline forms a hydrogen bond to another phenanthroline molecule. The third phenanthroline is not involved in any hydrogen bond at all. The C—N—C angle at the protonated N atom is significantly larger than the corresponding angle at the non-protonated N atoms. Comparing the structure of the title compound with four similar structures it was found that the the angle between the phenanthroline molecules forming the hydrogen bond correlates with the distance between the two N atoms: with an increasing angle between the aromatic ring systems the NN distance decreases. For the Cl− ion six contacts less than 3 Å to H atoms (bound to C atoms) are observed.