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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Infrared Spectroscopy of Matrix-Isolated Polycyclic Aromatic Compounds and Their Ions. 6. Polycyclic Aromatic Nitrogen Heterocycles
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Infrared Spectroscopy of Matrix-Isolated Polycyclic Aromatic Compounds and Their Ions. 6. Polycyclic Aromatic Nitrogen Heterocycles

机译：基质分离的多环芳族化合物及其离子的红外光谱。 6.多环芳族氮杂环

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摘要

The matrix-isolation technique has been employed to measure the mid-infrared spectra of several polycyclic-aromatic nitrogen heterocycles in both neutral and cationic forms. The species studied include: 7,8-benzoquinoline (C_(13)H_9N), 2-azapyrene (C_(15)H_9N), 1- and 2- azabenz[a]anthracene (C_(17)H_(11)N), and 1-, 2-, and 4-azachrysene (also C_(17)H_(11)N). The experimentally measured band frequencies and intensities for each molecule are tabulated and compared with their calculated values computed using density functional theory at the B3LYP/4-31G level. The overall agreement between experiment and theory is good, in keeping with previous investigations involving the parent aromatic hydrocarbons. Several interesting spectroscopic trends are found to accompany nitrogen substitution into the aromatic framework of these compounds. For the neutral species, the nitrogen atom produces a significant increase in the total integrated infrared intensity across the 1600-1100 cm~(-1) region and plays an essential role in the molecular vibration that underlies an uncharacteristically intense, discrete feature that is observed near 1400 cm~(-1) in the spectra of 7,8-benzoquinoline, 1-azabenz[a]-anthracene, and 4-azachrysene. The origin of this enhanced infrared activity and the nature of the 1400 cm~(-1) vibrational mode are explored. As a secondary result of the computations, the computed dipole moments and rotational constants for the species under study are reported. The dipole moments calculated are significantly stronger than those of the parent PAH and in principle could facilitate interstellar detection of these PAH related compounds.
机译：基质分离技术已用于测量中性和阳离子形式的几种多环芳族氮杂环的中红外光谱。研究的物种包括：7,8-苯并喹啉（C_（13）H_9N），2-氮杂ap（C_（15）H_9N），1-和2-氮杂苯并[a]蒽（C_（17）H_（11）N）以及1-，2-和4-氮杂环丁烯（也为C_（17）H_（11）N）。将每个分子的实验测得的谱带频率和强度制成表格，并与使用密度泛函理论在B3LYP / 4-31G水平上计算出的计算值进行比较。实验和理论之间的总体一致性很好，与先前涉及母体芳烃的研究保持一致。发现一些有趣的光谱趋势伴随着氮取代进入这些化合物的芳族骨架。对于中性物质，氮原子在整个1600-1100 cm〜（-1）区域内的总积分红外强度显着增加，并且在分子振动中起着至关重要的作用，而分子振动是观察到的异常强的离散特征的基础7,8-苯并喹啉，1-氮杂苯并[a]-蒽和4-氮杂环丁烯的光谱中接近1400 cm〜（-1）。探讨了这种增强的红外活动的起源以及1400 cm〜（-1）振动模式的性质。作为计算的次要结果，报告了所研究物种的偶极矩和旋转常数。计算出的偶极矩明显强于母体PAH的偶极矩，并且原则上可以促进星际探测这些PAH相关化合物。

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