Solid State Photochemistry of Hydroxylated Naphthalenes on Minerals: Probing Polycyclic Aromatic Hydrocarbon Transformation Pathways under Astrochemically-Relevant Conditions,ACS Earth and Space Chemistry

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Solid State Photochemistry of Hydroxylated Naphthalenes on Minerals: Probing Polycyclic Aromatic Hydrocarbon Transformation Pathways under Astrochemically-Relevant Conditions
ACS Earth and Space Chemistry ( IF 2.9 ) Pub Date : 2018-08-13 00:00:00 , DOI: 10.1021/acsearthspacechem.8b00060
Simone Potenti ₁ , Paola Manini ₂ , Teresa Fornaro ₃ , Giovanni Poggiali _{4,

5} , Orlando Crescenzi ₂ , Alessandra Napolitano ₂ , John R. Brucato ₅ , Vincenzo Barone ₁ , Marco d’Ischia ₂

Affiliation

Oxygenated derivatives of polycyclic aromatic hydrocarbons (PAHs), or oxyPAHs, recently captured the interest of the scientific community for their photochemical reactivity in a water–ice matrix mimicking the interstellar medium. Furthermore, oxyPAHs are interesting molecules for the study of the origin of life for their prebiotic potential. However, their stability and transformation pathways under astrophysically relevant conditions have remained largely unexplored. Herein we report the photochemical behavior of 1-naphthol (1-HN) and 1,6- and 1,8-dihydroxynaphthalene (DHN) either as pure powdered solids or adsorbed on forsterite or anatase surface. All the compounds showed an extensive decrease of main vibrational bands, accompanied in the case of DHNs by the formation of new molecular species. Irradiation of 1,8-DHN at 80 K resulted in the IR-detectable generation of CO₂ (2340 cm^–1), a process reported by other authors following irradiation of PAHs in water–ice analogues at 14 K. These results, when compared to model autoxidation experiments, indicated a high susceptibility of hydroxylated naphthalene derivatives to UV radiation leading to free radical and carbonyl-containing extended quinone intermediates (preliminary DFT calculations) with partial degradation and decarboxylation. On the basis of these results, oxyPAH formation and photoprocessing on minerals is proposed as a plausible pathway of PAHs transformation under astrochemical conditions of prebiotic relevance.

中文翻译：

矿物上羟基化萘的固态光化学：在与星光化学有关的条件下探索多环芳烃转化途径

最近，多环芳烃（PAHs）的含氧衍生物或oxyPAHs在模仿星际介质的水冰基质中的光化学反应性引起了科学界的兴趣。此外，oxyPAHs是研究益生元潜力的生命起源的有趣分子。然而，它们在天文学相关条件下的稳定性和转化途径仍未得到充分探索。在这里，我们报告1-萘酚（1-HN）和1,6-和1,8-二羟基萘（DHN）的光化学行为为纯粉状固体或吸附在镁橄榄石或锐钛矿表面上。所有化合物均显示出主要振动带的广泛减少，在DHN的情况下，伴随着新分子物种的形成。辐照1₂（2340 cm ^–1），这是其他作者在水冰类似物中以14 K照射多环芳烃后所报告的一个过程。与模型自氧化实验相比，这些结果表明羟基萘衍生物对紫外线的敏感性很高，从而导致自由基和含羰基的扩展醌中间体（初步DFT计算），具有部分降解和脱羧作用。根据这些结果，提出了在矿物上的益生元条件下，PAHs转化的可能途径是在矿物上形成oxyPAH和对其进行光处理。

更新日期：2018-08-13

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