Alam Mohammad Sayed, Lee Dong-Ung
Division of Bioscience, Dongguk University, Gyeongju 780-714, Republic of Korea; Department of Chemistry, Jagannath University, Dhaka 1100, Bangladesh.
Division of Bioscience, Dongguk University, Gyeongju 780-714, Republic of Korea.
Spectrochim Acta A Mol Biomol Spectrosc. 2015 Jun 15;145:563-574. doi: 10.1016/j.saa.2015.03.071. Epub 2015 Mar 13.
Two hydrazone Schiff base analogues, namely, (E)-N'-(4-hydroxy-3-methoxybenzylidene)benzohydrazide (3a) and (E)-N'-(4-methoxybenzylidene)benzohydrazide (3b), were synthesized using a mild, efficient method and characterized by (1)H NMR, mass spectrometry, elemental analysis, and single-crystal X-ray diffraction. X-ray analysis of a single crystal of 3a revealed a tetragonal, space group I4(1)/a structure, with an E-configuration around the azomethine (C8N2) double bond. In this structure, the NH and OH groups act as proton donors and the >CO and N groups as proton acceptors, and these facilitate hydrogen bond formation in the crystal state. Plausible intermolecular interactions were studied using 3D Hirshfeld surfaces and related 2D fingerprint plots. The optimized geometry, vibrational frequencies, Mulliken charge distribution, molecular electrostatic potential (MEP) maps, frontier molecular orbitals (FMOs), and associated energies of the ground state and the first single excited state were calculated using density functional theory (DFT) and time-dependant DFT calculations using the B3LYP/6-311G method. Vibrational frequencies calculated in the gaseous phase compared with experimental values measured in the solid state and showed good agreement with each other. The chemical reactivities of 3a and 3b were predicted by mapping MEP surface over optimized geometries and comparing these with MEP map generated over crystal structures. Mulliken charge distribution analysis and MEP map of 3a and 3b revealed that N(1), O(1), O(2) and O(3) atoms could act as electron donors and coordinate with metals and that these represented the most suitable sites for electrophilic attack. In fluorescence spectra, the absorption and emission spectra of 3a and 3b were similar in different polar solvents with few exceptions. In addition, both compounds exhibited dual emission spectra in acetone due to keto-enol tautomerism induced by photoexcitation.
采用温和、高效的方法合成了两种腙 Schiff 碱类似物，即 (E)-N'-(4-羟基-3-甲氧基亚苄基)苯甲酰肼(3a)和 (E)-N'-(4-甲氧基亚苄基)苯甲酰肼(3b)，并通过¹H NMR、质谱、元素分析和单晶 X 射线衍射对其进行了表征。3a 单晶的 X 射线分析显示其为四方晶系，空间群为 I4(1)/a 结构，甲亚胺(C8N2)双键周围为 E 构型。在该结构中，NH 和 OH 基团作为质子供体，>CO 和 N 基团作为质子受体，这些有助于在晶体状态下形成氢键。使用三维 Hirshfeld 表面和相关的二维指纹图谱研究了可能的分子间相互作用。采用密度泛函理论(DFT)和使用 B3LYP/6-311G 方法的含时 DFT 计算，计算了优化几何结构、振动频率、Mulliken 电荷分布、分子静电势(MEP)图、前线分子轨道(FMOs)以及基态和第一单重激发态的相关能量。气相中计算的振动频率与固态中测量的实验值进行比较，结果显示两者吻合良好。通过在优化几何结构上绘制 MEP 表面并将其与晶体结构上生成的 MEP 图进行比较，预测了 3a 和 3b 的化学反应性。3a 和 3b 的 Mulliken 电荷分布分析和 MEP 图表明，N(1)、O(1)、O(2)和 O(3)原子可作为电子供体与金属配位，这些是亲电攻击的最合适位点。在荧光光谱中，3a 和 3b 在不同极性溶剂中的吸收光谱和发射光谱相似，仅有少数例外。此外，由于光激发诱导的酮-烯醇互变异构，两种化合物在丙酮中均表现出双发射光谱。
