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首页> 外文期刊>Journal of chemical crystallography >Crystal, Molecular Structure and DFT Study of 2,6,7-Trimethyl-3-p-tolylquinoxaline and 2-(4-Methoxyphenyl)-3,6,7-trimethylquinoxaline
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Crystal, Molecular Structure and DFT Study of 2,6,7-Trimethyl-3-p-tolylquinoxaline and 2-(4-Methoxyphenyl)-3,6,7-trimethylquinoxaline

机译：2,6,7-三甲基-3-对甲苯基喹喔啉和2-（4-甲氧基苯基）-3,6,7-三甲基喹喔啉的晶体，分子结构和DFT研究

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摘要

The molecular structure of 2,6,7-trimethyl-3-p-tolylquinoxaline (hereafter denoted I) was confirmed by single crystal X-ray structure analysis. In the title compound, C18H18N2, I, the quinoxaline ring systemis essentially planar. The phenyl ring at the 2-position makes a dihedral angle of 40.23 degrees with the quinoxaline mean plane. In the crystal, molecules are linked into layers mainly by H2C-H center dot center dot center dot pi and (pi) C-H center dot center dot center dot pi interactions. Stacking pi center dot center dot center dot pi interactions are absent in the structure. The experimental and theoretical structural aspects of I and the recently reported methoxy derivative, 2-(4-methoxyphenyl)-3,6,7-trimethylquinoxaline, II, have been investigated and compared. Experimental geometric parameters (bond lengths and bond angles and dihedral angles) were compared with computed values from density functional theory with B3LY6-31G(d, p) basis set. Results show that values are in good agreement. The highest occupied molecular orbitals(HOMO) and lowest unoccupied molecular orbitals (LUMO) energies have been also calculated and used to determine the charge transfer within the molecule. MEP surfaces analyses were performed by the DFT method. From the MEP map, negative region is mainly localized over the electronegative nitrogen atoms (in I), and the nitrogen and oxygen atoms (in II) and the maximum positive region is localized on the methyl groups. These surfaces seem to correlate well with the intermolecular interactions in the lattice. Time-dependent density functional theory has been carried out to study the UV spectra of both molecules in gas phase and in methanol using polarizable continuum model and the results are presented and discussed. Graphical Abstract Crystal, molecular structure, crystal supramolecularity and DFT calculations of 2,6,7-Trimethyl-3-p-tolylquinoxaline and 2-(4-Methoxyphenyl)-3,6,7-trimethylquinoxaline are reported.
机译：通过单晶X射线结构分析确认了2,6,7-三甲基-3-对甲苯基喹喔啉的分子结构（以下称为I）。在标题化合物C18H18N2，I中，喹喔啉环系基本上是平面的。在2位的苯环与喹喔啉平均平面的二面角为40.23度。在晶体中，分子主要通过H2C-H中心点中心点中心点pi和（pi）C-H中心点中心点中心点pi相互作用连接成层。在结构中不存在堆叠pi中心点pi中心点pi交互作用的情况。研究和比较了I和最近报道的甲氧基衍生物2-（4-甲氧基苯基）-3,6,7-三甲基喹喔啉II的实验和理论结构。将实验几何参数（键长，键角和二面角）与基于B3LY6-31G（d，p）的密度泛函理论的计算值进行了比较。结果表明，价值观是一致的。还计算了最高占据分子轨道（HOMO）和最低未占据分子轨道（LUMO）的能量，并将其用于确定分子内的电荷转移。通过DFT方法进行MEP表面分析。从MEP图来看，负区主要位于负电性氮原子上（I中），而氮原子和氧原子（II中）和最大正区均位于甲基上。这些表面似乎与晶格中的分子间相互作用密切相关。运用时变密度泛函理论，利用可极化连续谱模型研究了气相和甲醇中分子的紫外光谱，并给出了结果并进行了讨论。报告了2,6,7-三甲基-3-对甲苯基喹喔啉和2-（4-甲氧基苯基）-3,6,7-三甲基喹喔啉的晶体，分子结构，晶体超分子性和DFT计算。

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