CRYSTAL STRUCTURE OF 2,7-DIMETHOXY-1,8-BIS(1-NAPHTHOYL)NAPHTHALENE: COOPERATIVE HYDROGEN BONDS AND THE ROLE IN THE MOLECULAR PACKING
The aromatic rings in 2,7-dimethoxy-1,8-bis(1-naphthoyl)naphthalene in crystal accumulate non-coplanarly to each other, with the dihedral angle between the terminal naphthalene and the 2,7-dimethoxynaphthalene rings of closer to 90˚ than the homologous compounds, 1,8-dibenzoyl-2,7-dimethoxynaphthalene and 2,7-dimethoxy-1,8-bis(2-naphthoyl)naphthalene. Molecular packing structures of the title compound and the homologous two compounds are classified by screw-sense and orientation of molecular assembly with a two-fold screw axis. In the title compound, right(left)-handed 21 helical assemblies are oriented in same direction and aligned to form a plane. The plane is alternately stacked with the counter handed version. On the other hand, right(left)-handed 21 helical assemblies are oppositely oriented to each other in the homologous two compounds. In the right(left)-handed 21 helical assembly of the title compound, two types of effective C–H…O=C hydrogen bonds are observed, i.e., (sp3)C–H…O=C hydrogen bond and (sp2)C–H…O=C hydrogen bond. However, either of two types of C–H…O=C hydrogen bonds is found in a right(left)-handed 21 helical assembly of the homologous two compounds. Besides, the title compound has (sp3)C–H…O=C hydrogen bonds between the right-handed 21 helical assembly and the left-handed one, the homologous two compounds have effective pi…pi stacking interactions and (sp2)C–H…O=C hydrogen bonds. When two types of C–H…O=C hydrogen bonds cooperatively stabilize the right(left)-handed 21 helical assembly, the helical assemblies are oriented in single direction to form a plane. Presence of pi…pi stacking interaction between the right-handed 21 helical assembly and the counter handed one apparently mask the effect of C–H…O=C hydrogen bonds to molecular packing to block a plane composed of single-handed 21 helical assembly.
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