Abstract
To explore the effect of the nature of substitutions on the structural parameters and hydrogen-bond inter-actions in N-acyl-hydrazone derivatives, the crystal structures of three ortho-substituted N-acyl-hydrazone derivatives, namely (E)-N-{2-[2-(2-chloro-benzyl-idene)hydrazin-yl]-2-oxoeth-yl}-4-methyl-benzene-sulfon-amide, C16H16ClN3O3S (I), (E)-N-{2-[2-(2-methyl-benzyl-idene)hydrazin-yl]-2-oxoeth-yl}-4-methyl-benzene-sulfonamide, C17H19N3O3S (II), and (E)-N-{2-[2-(2-nitro-benzyl-idene)hydrazin-yl]-2-oxoeth-yl}-4-methyl-benzene-sulfonamide, C16H16N4O5S (III), have been determined. The structures of the three compounds display similar mol-ecular conformations and hydrogen-bond patterns. The hydrazone part of the mol-ecule, C-C-N-N=C, is almost planar in all the compounds, with the C-C-N-N and C-N-N=C torsion angles being 179.5 (3) and 177.1 (3)°, respectively, in (I), -179.4 (2) and -177.1 (3)° in (II) and -179.7 (2) and 173.4 (2)° in (III). The two phenyl rings on either side of the chain are approximately parallel to each other. In the crystal, the mol-ecules are linked to each other via N-H⋯O hydrogen bonds, forming ribbons with R22(8) and R22(10) ring motifs. The introduction of electron-withdrawing groups (by a chloro or nitro group) to produce compounds (I) or (III) results in C-H⋯O hydrogen-bonding inter-actions involving the sulfonyl O atoms of adjacent ribbons, forming layers parallel to the ab plane in (I) or a three-dimensional network in (III). In (III), one O atom of the nitro group is disordered over two orientations with refined occupancy ratio of 0.836 (12):0.164 (12).
Highlights
To explore the effect of the nature of substitutions on the structural parameters and hydrogen-bond interactions in N-acylhydrazone derivatives, the crystal structures of three ortho-substituted N-acylhydrazone derivatives, namely (E)N-{2-[2-(2-chlorobenzylidene)hydrazinyl]-2-oxoethyl}-4-methylbenzenesulfonamide, C16H16ClN3O3S (I), (E)-N-{2-[2-(2-methylbenzylidene)hydrazinyl]-2oxoethyl}-4-methylbenzenesulfonamide, C17H19N3O3S (II), and (E)-N-{2-[2-(2nitrobenzylidene)hydrazinyl]-2-oxoethyl}-4-methylbenzenesulfonamide, C16H16N4O5S (III), have been determined
N-Acylhydrazones can exist as Z/E geometrical isomers about the C N bond of the hydrazone moiety (Palla et al, 1986)
Crystal-structure studies of N-acylhydrazones revealed that the molecules display an E conformation in the solid state (Purandara et al, 2015a,b,c, 2017; Gu et al 2012), whereas NMR spectroscopic studies showed the duplicate signals for amide and methylene protons, indicating the presence of two isomers in solution (Lacerda et al, 2012; Lopes et al, 2013)
Summary
N-Acylhydrazones belong to the Schiff base family of general structure R1—C( O)—N—N CR3R4. 3. Supramolecular features In all three compounds, the O atom of the carbonyl group is engaged as an acceptor in bifurcated N—HÁ Á ÁO hydrogen bonding with the sulfonamide H atom and the amino H atom of the hydrazide segment of two centrosymmetrically related neighbouring molecules, enclosing rings of R22(8) and R22(10) graph-set motif and forming molecular ribbons parallel to the a axis [Table 1, Fig. 4 for (I), Table 2, Fig. 6 for (II) and Table 3, Fig. 7 for (III)]. Adjacent ribbons in (III) are further linked into a three-dimensional network by weak hydrogen-bonding interactions occurring between methyl H atoms and the oxygen atom O5 of the nitro group, resulting in the formation of R22(34) ring motifs (Fig. 8). Database survey Comparison of structures (I)–(III) with those of the related Nacylhydrazone derivatives (E)-N-{2-[2-(4-methylbenzylidene)hydrazin-1-yl]-2-oxoethyl}-p-toluenesulfonamide (IV) (Purandara et al, 2015b) and (E)-N-2-[2-(4-nitrobenzylidene)hydrazine-1-yl]-2-oxoethyl-4-methylbenzenesulfonamide N,N-dimethylformamide monosolvate (V) (Purandara et al, 2017) indicate that molecules of ortho-substituted compounds are U-shaped, while the molecules of compounds (IV) and (V) have an extended chain conformation
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