(E)-2-{[(2-Amino­phen­yl)imino]­meth­yl}-5-(benz­yl­oxy)phenol and (Z)-3-benz­yl­oxy-6-{[(5-chloro-2-hy­droxy­phen­yl)amino]­methyl­idene}cyclo­hexa-2,4-dien-1-one

摘要

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). Compound (I) adopts the enol–imine tautomeric form with an E configuration about the C=N imine bond. In contrast, the o-hy­droxy Schiff base (II), is in the keto–imine tautomeric form with a Z configuration about the CH—NH bond. Neither mol­ecule is planar. In (I), the central benzene ring makes dihedral angles of 46.80 (10) and 78.19 (10)° with the outer phenyl­amine and phenyl rings, respectively, while for (II), the corresponding angles are 5.11 (9) and 58.42 (11)°, respectively. The mol­ecular structures of both compounds are affected by the formation of intra­molecular 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 mol­ecules along the b-axis direction. Mol­ecules are further linked by C—H⋯π inter­actions 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 anti­oxidant capacities of both compounds were determined by the cupric reducing anti­oxidant capacity (CUPRAC) process.