Ghichi Nadir, Benboudiaf Ali, Bensouici Chawki, DJebli Yacine, Merazig Hocine
Unit of Research CHEMS, University of Constantine 1, Algeria.
Biotechnology Research Center, Constantine, Algeria.
Acta Crystallogr E Crystallogr Commun. 2018 Apr 27;74(Pt 5):737-742. doi: 10.1107/S2056989018005662. eCollection 2018 May 1.
The title Schiff base compounds, CHNO (I) and CHClNO (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 configuration about the C=N imine bond. In contrast, the -hy-droxy Schiff base (II), is in the keto-imine tautomeric form with a 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 (6) ring motif. In the crystal of (I), strong N-H⋯O hydrogen bonds form zigzag chains of mol-ecules along the 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() 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.
席夫碱化合物CHNO（I）和CHClNO（II）由4-苄氧基-2-羟基苯甲醛与1,2-二氨基苯反应合成（I），与2-氨基-4-氯苯酚缩合合成（II）。化合物（I）采用烯醇-亚胺互变异构形式，C=N亚胺键周围具有构型。相比之下，羟基席夫碱（II）处于酮-亚胺互变异构形式，CH-NH键周围具有构型。两个分子都不是平面的。在（I）中，中心苯环与外部苯胺环和苯环的二面角分别为46.80（10）°和78.19（10）°，而对于（II），相应的角度分别为5.11（9）°和58.42（11）°。两种化合物的分子结构都受到分子内接触形成的影响，（I）形成O-H⋯N氢键，（II）形成N-H⋯O氢键；每个接触都产生一个（6）环基序。在（I）的晶体中，强N-H⋯O氢键沿轴方向形成锯齿状分子链。分子通过C-H⋯π相互作用和偏移π-π接触进一步连接，这些共同形成三维网络。在B3LYP/6-311+G（）水平下，化合物（II）的密度泛函理论（DFT）优化结构证实，在结构测定中发现的化合物的酮互变异构形式是能量最低的形式。两种化合物的抗氧化能力通过铜还原抗氧化能力（CUPRAC）方法测定。
