Crystal Structure and Solution Structural Dynamic Feature of 1,8-Dibenzoyl-2,7-Dimethoxynaphthalene

Abstract

The crystal structure and the dynamic feature of molecular structure in solution for 1,8-dibenzoyl-2,7-dimethoxynaphthalene are revealed by X-ray crystallographic analysis and VT-NMR measurements. In crystal, the molecule of the title compound is located on a twofold rotation axis. The two benzoyl groups are situated in an opposite direction. The dihedral angle between the mean planes of the phenyl ring and the naphthalene ring system is 80.25(6)˚. The benzene ring and carbonyl moiety in each benzoyl group are almost coplanar. The molecular packing is stabilized by weak C-H…O hydrogen bonds and a π-π stacking interaction between the benzene rings [centroid-centroid and interplanar distances of 3.6383(10) and 3.294 Å, respectively]. In solution, the temperature-dependent rotation behavior of the C-C bond between the benzene ring and the ketonic carbonyl group has been observed by 1 H VT-NMR measurements. Furthermore, comparison of the C-C bond rotation behavior between the benzene ring and the carbonyl group with 1-benzoyl-2,7-dimethoxynaphthalene has clarified that the C-C bond between the ketonic carbonyl group and the naphthalene ring rotates slower than the 1,8-dibenzoylated homologue.

1-[(Anthracen-9-yl)carbonyl]-2,7-dimethoxynaphthalene: a chain-like structure composed of face-to-face type dimeric molecular aggregates

“…Accordingly, a coplanar alignment of the aromatic rings in a molecule is not possible in peri-aroylnaphthalene compounds because of their highly congested molecular arrangement. On the other hand, the spatial organization around the ketonic carbonyl groups of a diaryl ketone structure is supposed to be rather loose compared to that of directly combined aromatic ring systems, as shown in the rotation barrier for an analogous compound in solution (Okamoto et al, 2012). In this regard, the expected flexibility of the aromatic ketone compound probably shows great variation in the molecular and packing structures in the crystal.…”

Crystal structure of 1-(2-fluorobenzoyl)-2,7-dimethoxynaphthalene

“…For example, biphenyl and binaphthyl are applied to optically active molecular catalysts and polymer materials on the basis of their axial chiralities (Pravas et al, 2013). In the course of our study on selective electrophilic aromatic aroylation of 2,7-dimethoxynaphthalene, it was found that peri-aroylnaphthalene compounds are formed regioselectively with the aid of suitable acidic mediators (Okamoto & Yonezawa, 2009;Okamoto et al, 2012). The X-ray analyses of peri-aroylnaphthalene compounds revealed that the aroyl groups at the 1-and 8-positions of the naphthalene ring systems are connected almost perpendicularly but the benzene rings of the aroyl groups tilt slightly toward the exo sides of the naphthalene ring systems, as observed in 1,8-dibenzoyl-2,7-dimethoxynaphthalene (Nakaema et al, 2008) and (2,7dimethoxynaphthalene-1,8-diyl)bis(4-fluorobenzoyl)dimethanone (Watanabe et al, 2010).…”

Crystal structure of 1-(4-hydroxybenzoyl)-2,7-dimethoxynaphthalene: Contribution of classical and non-classical hydrogen bonding interactions to the molecular packing structure

“…In the molecular packing of peri-aroylnaphthalene compounds, four kinds of non-covalent-bonding interactions, (sp 2 )C-H···O=C hydrogen bond, (sp 3 )C-H···O hydrogen bond, C-H···π hydrogen-bonding interaction, and π···π stacking are observed in decreasing order of frequency [12]. In solution, various conformations of aroyl groups in peri-aroylnaphthalene compounds are formed around the carbon-carbon bond between the carbonyl group and the naphthalene ring [13]. In this regard, the expected flexibility of the aromatic ketone compound probably shows great variation in single molecular and packing structures in the crystal.…”

“…Chemical shifts are expressed in ppm relative to internal standard of Me4Si (δ, 0.00). 13 C NMR spectra were recorded on a JEOL ECX400 spectrometer (100 MHz). Chemical shifts are expressed in ppm relative to internal standard of CDCl3 (δ, 77.0).…”