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DIMERIC MOLECULAR AGGREGATION MOTIF IN CRYSTAL OF 2,7-DIETHOXY-1-(4-NITROBENZOYL)NAPHTHALENE: CORRELATION OF SINGLE MOLECULAR STRUCTURE, MOLECULAR ACCUMULATION STRUCTURE AND NONCOVALENT-BONDING INTERACTION

DIMERIC MOLECULAR AGGREGATION MOTIF IN CRYSTAL OF 2,7-DIETHOXY-1-(4-NITROBENZOYL)NAPHTHALENE: CORRELATION OF SINGLE MOLECULAR STRUCTURE, MOLECULAR ACCUMULATION STRUCTURE AND NONCOVALENT-BONDING INTERACTION

Author: Shinji Ohisa, Mayumi Saeki, Hirokazu Shiomichi, Noriyuki Yonezawa, Akiko Okamoto
Abstract

Crystal structure of 2,7-diethoxy-1-(4-nitrobenzoyl)naphthalene C21H19NO5, is reported and discussed on the characteristics of the spatial organization of single molecule and molecular aggregation as contrasted with a homologous compound. The molecular structures of these compounds differ only in the kind of alkoxy group of 2,7-positions of the naphthalene rings, i.e., ethoxy groups for title compound and methoxy groups for homologue. In single molecular crystal structures of these compounds, 4-nitrobenzoyl group is non-coplanarly attached to the naphthalene ring. The molecules exhibit axial chirality, with either R or S stereogenic axis. The two pairs of the enantiomeric molecules are related by two-fold helical axis in the asymmetric unit of P21/n space group for title compound and P21/c one for homologue, showing the number of molecules (Z) is four for both compounds. In their molecular packing structures, (R)- and (S)- enantiomers are connected to each other by … stacking interactions, forming centrosymmetric dimeric molecular aggregates. However, the aggregation structures of the dimers are apparently different between title compound and homologue. The dimeric units of title compound are stacked into columnar structure with (sp2 )C–H…O=C non-classical hydrogen bonds between identical enantiomers along aaxis. The columns are connected by (sp2 )C–H…OEt non-classical hydrogen bonds between identical enantiomers along c-axis to give sheet-like aggregation spreading on ac-plane. The sheets are piled up through (sp3
)C–H… non-classical hydrogen bonds between opposite enantiomeric molecules of next dimeric aggregates along b-axis giving layers. On the other hand, the dimeric molecular aggregates of homologue are connected into flattish column by (sp3
)C–H…O=C non-classical hydrogen bonds and (sp3)C–H… nonclassical hydrogen bonds between identical enantiomers. The columns are linked into waving plate through weak (sp2 )C–H… nonclassical hydrogen bonds. In title compound, difference between … stacking interactions and non-classical hydrogen bonds is smaller than homologue in contribution to the whole of molecular packing structure.

Keywords: Centrosymmetric dimeric molecular aggregate, molecular motif, non-classical hydrogen bonds, … stacking interaction

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