Synthesis, Molecular Structure and Antioxidant Activity of (E)-4-[Benzylideneamino]-1,5-dimethyl-2-phenyl-1H-pyrazol-3(2H)-one, a Schiff Base Ligand of 4-Aminoantipyrine
作者:Mohammad Sayed Alam、Dong-Ung Lee
DOI:10.1007/s10870-011-0209-1
日期:2012.2
In this study, the title compound, C18H17N3O (M r = 291.35), was synthesized by the condensation reaction of 4-amino-1,5-dimethyl-2-phenylpyrazole-3-one and benzaldehyde. Single-crystal X-ray diffraction data revealed that this compound adopts a trans configuration around the central C=N double bond. It crystallizes in the monoclinic, space group P21/c with a = 12.9236(17) Å, b = 6.8349(9) Å, c = 17.072(2) Å, β = 90.316(3)°, V = 1508.0(3) Å3, Z = 4, D c = 1.283 Mg/m3, F(000) = 616, μ = 0.082 mm−1, R = 0.0442, and wR = 0.0936. Two different planes exist within the molecule; e.g. the pyrazolone and benzylidene groups attached to C9 of the pyrazolone ring are almost coplanar, whereas the phenyl group attached to the N1 of the pyrazolone ring is in another plane. Density functional theory (DFT) and time-dependent DFT calculations were performed to predict the electronic structure and absorption spectra of (E)-4-[benzylideneamino]-1,5-dimethyl-2-phenyl-1H-pyrazol-3(2H)-one, a schiff base ligand of 4-aminoantipyrine using B3LYP/6-311G basis set on the AM1 optimized geometry. The predicted vibrational frequencies using the B3LYP/6-311G method were in strong agreement with the experimental IR spectra. The time dependent DFT calculations were used to evaluate the electronic absorption spectrum and three electron transition bands, which were mainly derived from the contribution of n → π* and π → π* transitions, were observed in both the experimental and predicted UV–Vis spectra. A maximum emission band at 370 nm was observed in the fluorescence spectra of the title compound. In addition, the title compound showed good DPPH antioxidant activity. The structure of title compound, C18H17N3O, had monoclinic (P21/c) symmetry and DFT studies were used to predict the electronic structure and absorption spectra using B3LYP/6-311G basis set on the AM1 optimized geometry as well as to help explain the proposed mechanism of DPPH antioxidant activity.
本研究通过 4-氨基-1,5-二甲基-2-苯基吡唑-3-酮和苯甲醛的缩合反应合成了标题化合物 C18H17N3O(M r = 291.35)。单晶 X 射线衍射数据显示,该化合物在中心 C=N 双键周围呈反式构型。它结晶于单斜晶系,空间群为 P21/c,a = 12.9236(17) 埃,b = 6.8349(9) 埃,c = 17.072(2) 埃,β = 90.316(3)°, V = 1508.0(3) Å3, Z = 4, D c = 1.283 Mg/m3, F(000) = 616, μ = 0.082 mm-1, R = 0.0442, and wR = 0.0936.分子内存在两个不同的平面;例如,吡唑酮环 C9 上的吡唑酮基团和苯亚甲基基团几乎共面,而吡唑酮环 N1 上的苯基基团则在另一个平面上。利用 AM1 优化几何的 B3LYP/6-311G 基集,对 4-氨基安替比林的片基配体 (E)-4-[benzylideneamino]-1,5-dimethyl-2-phenyl-1H-pyrazol-3(2H)-one 的电子结构和吸收光谱进行了密度泛函理论(DFT)和时变 DFT 计算。使用 B3LYP/6-311G 方法预测的振动频率与实验红外光谱非常吻合。实验和预测的紫外可见光谱中都观察到了三个电子过渡带,它们主要来自 n → π* 和 π → π* 转变。在标题化合物的荧光光谱中,在 370 nm 处观察到一个最大发射带。此外,标题化合物还具有良好的 DPPH 抗氧化活性。标题化合物 C18H17N3O 的结构具有单斜(P21/c)对称性,DFT 研究使用 AM1 优化几何结构上的 B3LYP/6-311G 基集预测了其电子结构和吸收光谱,并帮助解释了所提出的 DPPH 抗氧化活性机理。