Hamada Nagwa M M
Chemistry Department Faculty of Education Alexandria University Alexandria 21526 Egypt.
ChemistryOpen. 2018 Oct 12;7(10):814-823. doi: 10.1002/open.201800146. eCollection 2018 Oct.
In this study, 2-mercapto-3-phenyl-2,3-dihydro-1-quinazolin-4-one (), which exists as a thiol and thione tautomer, was treated with acetylacetone to give the target compound, namely, 1-methyl-5-phenyl-5-pyrido[1,2-]quinazoline-3,6-dione (). The spectroscopic data, including UV/Vis, IR, H NMR, C NMR, and mass data, of this compound were recorded. The molecular structures of the starting material () and the product () were optimized by using density functional theory (DFT) by employing the B3LYP exchange correlation with the 6-311G (d, p) and 6-31G++ (d, p) basis sets. The electronic spectra were determined based on time-dependent DFT calculations in three different solvents (i.e., chloroform, ethanol, and acetonitrile) starting from the same solvated run of the optimized geometry with the same two basis sets. The solvent effects were considered based on the polarizable continuum model (PCM), and the energetic behavior of the compounds and the total static dipole moment () in different solvents were examined in the two basis sets; the results showed that the total energy of the compounds decreased upon increasing the polarity of the solvent. Time-dependent DFT calculations were performed to analyze the electronic transitions for various excited states that reproduced the experimental band observed in the UV/Vis spectrum. A study on the electronic properties, such as the HOMO and LUMO energies, was performed by the time-independent DFT approach. Using the gauge-independent atomic orbital method (GIAO), the H NMR chemical shifts were calculated and correlated with the experimental ones. The computed results showed that the introduction of different dielectric media had a slight effect on the stability and reactivity of the title compound as well as on the Milliken atomic charges and the molecular geometry. Besides, the molecular electrostatic potential of target product was evaluated in different solvents.
在本研究中，以硫醇和硫酮互变异构体形式存在的2-巯基-3-苯基-2,3-二氢-1-喹唑啉-4-酮（）与乙酰丙酮反应，得到目标化合物，即1-甲基-5-苯基-5-吡啶并[1,2 - ]喹唑啉-3,6-二酮（）。记录了该化合物的光谱数据，包括紫外/可见光谱、红外光谱、氢核磁共振谱、碳核磁共振谱和质谱数据。通过使用密度泛函理论（DFT），采用B3LYP交换相关泛函以及6-311G(d, p)和6-31G++(d, p)基组，对起始原料（）和产物（）的分子结构进行了优化。基于含时密度泛函理论计算，从优化几何结构的同一溶剂化运行开始，使用相同的两个基组，在三种不同溶剂（即氯仿、乙醇和乙腈）中确定了电子光谱。基于极化连续介质模型（PCM）考虑了溶剂效应，并在两个基组中研究了化合物在不同溶剂中的能量行为和总静态偶极矩（）；结果表明，随着溶剂极性的增加，化合物的总能量降低。进行含时密度泛函理论计算以分析各种激发态的电子跃迁，这些跃迁重现了紫外/可见光谱中观察到的实验谱带。通过不含时密度泛函理论方法对诸如最高占据分子轨道（HOMO）和最低未占据分子轨道（LUMO）能量等电子性质进行了研究。使用规范无关原子轨道方法（GIAO）计算了氢核磁共振化学位移，并与实验值进行了关联。计算结果表明，引入不同的介电介质对标题化合物的稳定性和反应性以及米利肯原子电荷和分子几何结构有轻微影响。此外，还评估了目标产物在不同溶剂中的分子静电势。
