Cooperative and Anticooperative Effects in the Cocrystals of Mono- and Diazanaphthalenes with m eso -1,2-Diphenyl-1,2-ethanediol

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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···π 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 π-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···π 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···π 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.