Institute of Molecule and Crystal Physics-Subdivision of the Ufa Federal Research Centre of the Russian Academy of Sciences (IMCP UFRC RAS), Prospekt Oktyabrya 151, Ufa 450075, Russia.
A.N. Frumkin Institute of Physical Chemistry and Electrochemistry of the Russian Academy of Sciences (IPCE RAS), Leninsky prospect, 31k4, Moscow 199071, Russia.
J Chem Phys. 2019 Apr 7;150(13):134301. doi: 10.1063/1.5087182.
Macrocyclic tetrapyrrolic compounds, such as naturally occurring or artificial porphyrins and phthalocyanines, have unique and highly attractive properties for applications in medicine and technology. The interaction of free-base phthalocyanine (HPc) and tetraphenylporphyrin (HTPP) molecules with low-energy (0-15 eV) electrons was studied in vacuo by means of negative ion resonant electron capture mass spectrometry. Close similarities in formation and decay of negative ions of these compounds were revealed. Efficient formation of long-lived molecular negative ions (MNIs) was observed in the incident electron energy range of 0-8 eV, unprecedentedly wide for organic compounds and comparable to the range characteristic to carbon atomic clusters, fullerenes. Experiments testify to the strong persistence of MNIs of both compounds to dissociative decay, isomerization, and electron autodetachment. Lifetimes of MNIs as a function of incident electron energy were measured and it was concluded that the isolated anions may retain additional electrons in a time scale of up to hundreds of seconds at standard temperature due to the high adiabatic electron affinity of these large molecules. For the representatives of dyes and photochromic compounds comprehensively studied in terms of interaction with light, the present work highlights yet another unique property of these molecules, namely the capability to attach and durably retain an additional electron of low, pre-ionization energy.
大环四吡咯化合物，如天然或人工卟啉和酞菁，因其在医学和技术应用中的独特和极具吸引力的特性而备受关注。本研究采用真空负电子共振电子俘获质谱法研究了自由碱酞菁（HPc）和四苯基卟啉（HTPP）分子与低能（0-15 eV）电子的相互作用。揭示了这些化合物负离子形成和衰减的紧密相似性。在 0-8 eV 的入射电子能量范围内观察到长寿命分子负离子（MNIs）的有效形成，这在有机化合物中是前所未有的宽，与碳原子团簇、富勒烯的特征范围相当。实验证明了两种化合物的 MNIs 对离解衰变、异构化和电子自脱附具有很强的持久性。测量了 MNIs 作为入射电子能量函数的寿命，并得出结论，由于这些大分子的高绝热电子亲合势，孤立的阴离子可能在标准温度下的数百秒时间内保留额外的电子。对于作为与光相互作用的代表性染料和光致变色化合物进行了全面研究，本工作突出了这些分子的另一个独特性质，即能够附加和持久保留低预电离能的额外电子。
