Cooperative and anticooperative effects in the cocrystals of mono- and diazanaphthalenes with meso-1,2-diphenyl-1,2-ethanediol
Olenik, B; Boese, R; Sustmann, R
meso-1,2-Diphenyl-1,2-ethanediol (1) as a hydrogen-bond
donor and azanaphthalenes as hydrogen-bond acceptors form cocrystals, mostly in the ratio of 1:2.
The X-ray structures provide detailed information on the binding motifs that consist of strong
O-H...N hydrogen bonds and C-H...pi interactions between C-H bonds of the heterocycles and the
phenyl rings of meso-1,2-diphenyl-1,2-ethanediol. These motifs are found whenever a nitrogen atom
is in the 2-position of the naphthalene skeleton (isoquinoline (3), quinazoline (2), and
phthalazine (4)). Nitrogen atoms in the 1,3- and 2,3-positions, 1,3-diazanaphthalene
(quinazoline) (2) and 2,3-diazanaphthalene (phthalazine) (4), alter the crystal lattice only in
the case of phthalazine, due to additional hydrogen-bond- and pi-stacking interactions. If a
nitrogen atom is present in 1-position of naphthalene, 1,5-diazanaphthalene (naphthyridine) (5),
the bonding motif consists of O-H...N hydrogen bridges between the nitrogen atoms in the 1- and
5-positions and the O-H groups of 1 leading to infinite strings of alternating naphthyridine and
diol molecules. C-H...pi interactions are found in this case between C-H groups of the adjacent
six-membered ""pyridyl"" ring and the phenyl group attached to the carbon atom which is not
involved in the formation of O-H...N hydrogen bonds as in the other three cases. This motif
enables the incorporation of a second naphthyridine molecule without leading to additional
hydrogen bonds, but with two C-H...pi interactions. Attempts to generate cocrystals between 1 and
1-azanaphthalene (quinoline) as well as a tri-cocrystal between 1, 5, and naphthalene which
should be of interest in this context have failed so far. Further attempts at cocrystallization
of diazanaphthalenes with 1 also failed, which demonstrates the fine-tuned balance of cooperative
and anticooperative effects for secondary intermolecular interactions.