2-Hydroxybenzyl alcohol–phenanthroline (1/1)

Crystals of the title compound, C12H8N2·C7H8O2, were obtained during cocrystallization experiments of a compound with two hydrogen-bond donors (2-hydroxybenzyl alcohol) with another compound containing two hydrogen-bond acceptors (phenanthroline). Unexpectedly, the two molecules do not form dimers with two O—H⋯N hydrogen bonds connecting the two molecules. However, one of the hydroxy groups forms a bifurcated hydrogen bond to both phenanthroline N atoms, whereas the other hydroxy group forms an O—H⋯O hydrogen bond to a symmetry-equivalent 2-hydroxybenzyl alcohol molecule. In addition, the crystal packing is stabilized by π–π interactions between the two phenanthroline ring systems, with a centroid–centroid distance of 3.570  Å.

Crystals of the title compound, C 12 H 8 N 2 ÁC 7 H 8 O 2 , were obtained during cocrystallization experiments of a compound with two hydrogen-bond donors (2-hydroxybenzyl alcohol) with another compound containing two hydrogen-bond acceptors (phenanthroline). Unexpectedly, the two molecules do not form dimers with two O-HÁ Á ÁN hydrogen bonds connecting the two molecules. However, one of the hydroxy groups forms a bifurcated hydrogen bond to both phenanthroline N atoms, whereas the other hydroxy group forms an O-HÁ Á ÁO hydrogen bond to a symmetry-equivalent 2-hydroxybenzyl alcohol molecule. In addition, the crystal packing is stabilized byinteractions between the two phenanthroline ring systems, with a centroid-centroid distance of 3.570 Å .   Table 1 Hydrogen-bond geometry (Å , ).

Comment
The aim of our research is the cocrystallization of two small organic compounds in order to examine the hydrogen bonds formed between hydrogen-bond acceptors and hydrogen-bond donors (Ton & Bolte, 2005;Tutughamiarso et al., 2009). In this work, we wanted to cocrystallize phenanthroline and 2-hydroxybenzyl alcohol. However, the cocrystal, we obtained, did not show the expected AA/DD pattern, i.e. with two O-H···N hydrogen bonds connecting the two molecules to a dimer.
However, one of the hydroxy groups forms a bifurcated hydrogen bonds to both phenanthroline N atoms, whereas the other hydroxy group forms a O-H···O hydrogen bond to a symmetry equivalent 2-hydroxybenzyl alcohol molecule. In addition, the crystal packing is stabilized by π-π interactions between two phenanthroline ring systems forming a centrosymmetric dimer with a centroid···centroid distance of 3.570 Å. The second molecule is generated by the symmetry operation 1 -x, -y, 1 -z.

Experimental
The complex consisting of 1,10-phenanthroline and 2-hydroxybenzylenealcohol was obtained by to the method of isothermal vaporization. 1,10-phenanthroline and 2-hydroxybenzylenealcohol were added in an equimolar ratio (10 mmol) into a flask.
Afterwards chloroform was added dropwise until the substances were completely dissolved. Then, the flask was sealed and set aside at room temperature. After two weeks crystals of the complex were obtained.