Eltayeb Naser Eltaher, Teoh Siang Guan, Yeap Chin Sing, Fun Hoong-Kun, Adnan Rohana
Acta Crystallogr Sect E Struct Rep Online. 2009 Aug 8;65(Pt 9):o2065-6. doi: 10.1107/S1600536809029833.
The asymmetric unit of the title Schiff base compound, C(21)H(18)N(2)O(4), consists of four independent zwitterions (A, B, C and D) with similar conformations. In each independent mol-ecule, the methyl group is disordered over two positions; the occupancies of the two positions are 0.819 (5) and 0.181 (5) in mol-ecule A, 0.912 (5) and 0.088 (5) in B, 0.734 (5) and 0.266 (5) in C, and 0.940 (6) and 0.060 (6) in D. The dihydroxy-phenyl and the hydroxy-phenolate rings in mol-ecule A form dihedral angles of 17.36 (12) and 13.30 (12)°, respectively, with the central benzene ring, whereas the respective angles for mol-ecules B, C and D are 30.22 (11)/7.46 (11), 35.26 (12)/11.01 (12) and 39.89 (12)/4.29 (12)°. In all independent mol-ecules, intra-molecular N-H⋯O and O-H⋯N hydrogen bonds generate S(6) ring motifs. The four independent mol-ecules are linked into two pairs, viz. A-B and C-D, by inter-molecular O-H⋯O hydrogen bonds. These pairs are linked into a two-dimensional network parallel to the ab plane by C-H⋯O hydrogen bonds. In addition, C-H⋯π and π-π [centroid-centroid distance = 3.5153 (14)-3.7810 (15) Å] inter-actions stabilize the crystal structure.
标题席夫碱化合物C(21)H(18)N(2)O(4)的不对称单元由四个构象相似的独立两性离子（A、B、C和D）组成。在每个独立分子中，甲基在两个位置上无序；分子A中两个位置的占有率分别为0.819 (5)和0.181 (5)，分子B中为0.912 (5)和0.088 (5)，分子C中为0.734 (5)和0.266 (5)，分子D中为0.940 (6)和0.060 (6)。分子A中的二羟基苯基和羟基苯酚盐环与中心苯环分别形成17.36 (12)°和13.30 (12)°的二面角，而分子B、C和D的相应角度分别为30.22 (11)/7.46 (11)、35.26 (12)/11.01 (12)和39.89 (12)/4.29 (12)°。在所有独立分子中，分子内N-H⋯O和O-H⋯N氢键形成S(6)环基序。四个独立分子通过分子间O-H⋯O氢键连接成两对，即A-B和C-D。这些对通过C-H⋯O氢键连接成平行于ab平面的二维网络。此外，C-H⋯π和π-π[质心-质心距离 = 3.5153 (14)-3.7810 (15) Å]相互作用稳定了晶体结构。
