Abstract
The title Schiff base compounds, C20H18N2O2 (I) and C20H16ClNO3 (II), were synthesized from 4-benz-yloxy-2-hy-droxy-benzaldehyde by reaction with 1,2-di-amino-benzene for (I), and condensation with 2-amino-4-chloro-phenol for (II). Compound (I) adopts the enol-imine tautomeric form with an E configuration about the C=N imine bond. In contrast, the o-hy-droxy Schiff base (II), is in the keto-imine tautomeric form with a Z configuration about the CH-NH bond. Neither mol-ecule is planar. In (I), the central benzene ring makes dihedral angles of 46.80 (10) and 78.19 (10)° with the outer phenyl-amine and phenyl rings, respectively, while for (II), the corresponding angles are 5.11 (9) and 58.42 (11)°, respectively. The mol-ecular structures of both compounds are affected by the formation of intra-molecular contacts, an O-H⋯N hydrogen bond for (I) and an N-H⋯O hydrogen bond for (II); each contact generates an S(6) ring motif. In the crystal of (I), strong N-H⋯O hydrogen bonds form zigzag chains of mol-ecules along the b-axis direction. Mol-ecules are further linked by C-H⋯π inter-actions and offset π-π contacts and these combine to form a three-dimensional network. The density functional theory (DFT) optimized structure of compound (II), at the B3LYP/6-311+G(d) level, confirmed that the keto tautomeric form of the compound, as found in the structure determination, is the lowest energy form. The anti-oxidant capacities of both compounds were determined by the cupric reducing anti-oxidant capacity (CUPRAC) process.
Highlights
The title Schiff base compounds, C20H18N2O2 (I) and C20H16ClNO3 (II), were synthesized from 4-benzyloxy-2-hydroxybenzaldehyde by reaction with 1,2-diaminobenzene for (I), and condensation with 2-amino-4-chlorophenol for (II)
The molecular structures of both compounds are affected by the formation of intramolecular contacts, an O—HÁ Á ÁN hydrogen bond for (I) and an N—HÁ Á ÁO hydrogen bond for (II); each contact generates an S(6) ring motif
Weaker C—HÁ Á Á and offset – stacking interactions contribute to the packing (Fig. 4) [Cg2Á Á ÁCg2(Àx, y, Àz + 12) = 3.8151 (11) A ; Cg2 is the centroid of the central ring]
Summary
Schiff base compounds have been used as fine chemicals and medicinal substrates (Fun et al, 2011). Schiff base compounds exhibit a broad range of biological activities, including antifungal and antibacterial (da Silva et al, 2011). They are used as anion sensors (Dalapati et al, 2011; Khalil et al, 2009), non-linear optical compounds (Sun et al, 2012), and as versatile ligands in coordination chemistry (Khanmohammadi et al, 2009; Keypour et al, 2010). The common structural feature of these compounds is the presence of a benzyloxy substituent on the central ring, each molecule adopts a different tautomeric form. Symmetry codes: (i) Àx; Ày þ 1; Àz; (ii) Àx þ 2; Ày þ 2; Àz; (iii) Àx; Ày þ 1; Àz þ 1
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