Polycyclic aromatic hydrocarbons (PAHs) constitute an essential family of compounds in interstellar (ISM) and circumstellar (CSM) media. Recently, formation routes for the corresponding polycyclic aromatic phosphorus heterocycles (PAPHs) in astrophysical environments have been proposed. In order to contribute to a better understanding of the phosphorus chemistry in the ISM, infrared (IR) spectra and selected properties of PAPHs were computed at the density functional theory level for neutral, cationic, and anionic species. Our results reveal that several protonated PAPHs do not have planar backbones, and all species have permanent dipole moments between 2D and 4D. Closed-shell PAPHs have similar ionization potentials compared to the parent PAHs, below the Lyman threshold limit. In addition, all PAPHs show positive electron affinities higher than those of PAHs. Protonation preferably occurs on the heteroatom but with lower proton affinities than those of the corresponding nitrogen analogues (polycyclic aromatic nitrogen heterocycles). In general, neutral species have similar IR spectra profile with the most intense bands around 800 cm⁻¹ (12.5 μm) related to C−H wagging. Charge and protonation affect the IR spectra mainly by decreasing the intensities of these modes and increasing the ones between 1000 (10.0 μm) and 1800 cm⁻¹ (5.6 μm). The P−H stretching appears in a different spectral region, between 2300 (4.3 μm) and 2700 cm⁻¹ (3.7 μm). Our results are discussed in the context of distinct sources where PAHs and phosphorus are detected. PAPHs, in particular the coronene derivatives, can contribute to the unidentified infrared emission band at 6.2 μm.

中文翻译：

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中性和离子型多环芳族磷杂环（PAPH）的气相光谱表征

多环芳烃（PAH）是星际（ISM）和星际（CSM）介质中必不可少的化合物。近来，已经提出了在天体环境中相应的多环芳族磷杂环（PAPH）的形成途径。为了更好地理解ISM中的磷化学，我们在中性，阳离子和阴离子物质的密度泛函理论水平上计算了PAPH的红外（IR）光谱和选定的性能。我们的结果表明，一些质子化的PAPH没有平面骨架，并且所有物种在2D和4D之间都具有永久偶极矩。与母体PAH相比，闭壳PAPH具有相似的电离电势，低于Lyman阈值极限。此外，所有PAPH都显示出高于PAH的正电子亲和力。质子化优选发生在杂原子上，但是质子亲合力比相应的氮类似物（多环芳族氮杂环）低。通常，中性物质具有相似的红外光谱图，最强的波段在800厘米左右^-1（12.5 μ M）与C-H摆尾。电荷和质子化影响IR光谱主要是通过减小这些模式的强度和1000（10.0之间增加的那些μ M）和1800厘米^-1（5.6 μ M）。在P-H在不同光谱区域的拉伸出现，2300（4.3之间μ M）和2700厘米^-1（3.7 μ M）。我们的结果将在检测到PAHs和磷的不同来源的背景下进行讨论。PAPHs，特别是六苯并苯衍生物，可以在6.2向未识别的红外线发射带μ米。