Abstract
The crystal structures of three salicyaldoxime compounds, namely 2-hy-droxy-4-methyl-benzaldehyde oxime, C8H9NO2, 1, 2,4-di-hydroxy-benzaldehyde oxime, C7H7NO3, 2, and 2-hy-droxy-4-meth-oxy-benzaldehyde oxime, C8H9NO3, 3, are discussed. In each compound, the hydroxyl groups are essentially coplanar with their attached phenyl group. The inter-planar angles between the C=N-O moieties of the oxime unit and their attached phenyl rings are 0.08 (9), 1.08 (15) and 6.65 (15)° in 1, 2 and 3, respectively. In all three mol-ecules, the 2-hy-droxy group forms an intra-molecular O-H⋯N(oxime) hydrogen bond. In compound (1), inter-molecular O-H(oxime)⋯O(hydrox-yl) hydrogen bonds generate R 2 2(14) dimers, related by inversion centres. In compound 2, inter-molecular O-H(oxime)⋯O(4-hy-droxy) hydrogen bonds generate C9 chains along the b-axis direction, while O-H(4-hydrox-yl)⋯O(2-hydrox-yl) inter-actions form zigzag C6 spiral chains along the c-axis direction, generated by a screw axis at 1, y, 1/4: the combination of the two chains provides a bimolecular sheet running parallel to the b axis, which lies between 0-1/2 c and 1/2-1 c. In compound 3, similar C9 chains, along the b-axis direction are generated by O-H(oxime)⋯O(4-meth-oxy) hydrogen bonds. Further weaker, C-H⋯π (in 1), π-π (in 2) and both C-H⋯π and π-π inter-actions (in 3) further cement the three-dimensional structures. Hirshfeld surface and fingerprint analyses are discussed.
Highlights
The crystal structures of three salicyaldoxime compounds, namely 2-hydroxy-4methylbenzaldehyde oxime, C8H9NO2, 1, 2,4-dihydroxybenzaldehyde oxime, C7H7NO3, 2, and 2-hydroxy-4-methoxybenzaldehyde oxime, C8H9NO3, 3, are discussed
The hydroxyl groups are essentially coplanar with their attached phenyl group
In compound 2, intermolecular O—H(oxime)Á Á ÁO(4-hydroxy) hydrogen bonds generate C9 chains along the baxis direction, while O—H(4-hydroxyl)Á Á ÁO(2-hydroxyl) interactions form zigzag C6 spiral chains along the c-axis direction, generated by a screw axis at 1, y, 1/4: the combination of the two chains provides a bimolecular sheet running parallel to the b axis, which lies between 0–1/2 c and 1/2–1 c
Summary
RCH NOH, are found in many biologically active compounds (Abele et al, 2008; Nikitjuka & Jirgensons 2014), having a diverse range of uses including as anti-tumor agents (Martınez-Pascual et al, 2017; Qin et al, 2017; Canario et al, 2018; Huang et al, 2018), acaricidal and insecticidal agents (Dai et al, 2017), thymidine phosphorylase inhibitors (Zhao et al, 2018), anti-microbial agents (Yadav et al, 2017), bacteriocides (Kozlowska et al, 2017), anti-inflammatory agents (Mohassab et al, 2017) and in the treatment of nervegas poisoning (Lorke et al, 2008; Voicu et al, 2010; Katalinicet al., 2017; Radicet al., 2013). The compounds described are all salicylaldoxime derivatives (2-HO-4-X-C6H3-CH NOH) with different substituents in the 4-position, namely a methyl group, a hydroxy group and a methoxy group, respectively, in compounds, 1, 2 and 3. While the structures of many salicylaldoxime derivatives have been reported, the structures of very few compounds with an additional substituent in the 4 position are known. The full report will be published elsewhere (da Costa et al, 2018)
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