Department of Physics, Babasaheb Bhimrao Ambedkar University, Lucknow, 226 025, India.
Department of Physics, Banaras Hindu University, Varanasi, 221 005, India.
J Mol Model. 2021 Mar 24;27(4):112. doi: 10.1007/s00894-021-04737-w.
The hydroxyl and peroxyl radicals, particularly the former, occur abundantly and damage almost all types of materials. Polycyclic aromatic hydrocarbons (PAHs) and their polyradicals (all hydrogens removed) have been considered as models for graphene in some recent studies. Geometries of different adducts of polyradicals of two small PAHs having four and nine benzene rings with an OH or OOH radical each were optimized employing unrestricted density functional theory and two different density functionals. The ground states of all the adducts involving the PAHs had doublet spin multiplicity while those involving the polyradicals had doublet, quartet, sextet, or octet spin multiplicity that was decided on the basis of calculated minimum total energies for optimized geometries. Binding energies of the adducts of an OH or OOH radical at the different sites of the polyradicals of PAHs showed that the OH radical would bind with these systems much more strongly than the OOH radical while both the radicals would bind much more strongly with the polyradicals than with the PAHs. Furthermore, both the OH and OOH radicals are found to bind at the edges of the polyradicals much more strongly than at their interior sites. It is shown that polyradicals can serve as efficient scavengers of OH and OOH radicals and therefore, these materials can be used to protect both biological and non-biological systems from damage due to reactions with these radicals.
羟基和过氧自由基，特别是前者，大量存在并几乎对所有类型的物质造成损害。在最近的一些研究中，多环芳烃（PAHs）及其齐聚自由基（所有氢原子被去除）被认为是石墨烯的模型。采用非限制密度泛函理论和两种不同密度泛函，对两个含有四个和九个苯环的小 PAHs 的齐聚自由基与每个 OH 或 OOH 自由基的不同加合物的几何形状进行了优化。所有涉及 PAHs 的加合物的基态具有双重自旋多重性，而那些涉及齐聚自由基的加合物具有双重、四重、六重或八重自旋多重性，这是根据优化几何形状的计算总能量确定的。PAHs 齐聚自由基上不同位置的 OH 或 OOH 自由基加合物的结合能表明，OH 自由基与这些体系的结合强度远大于 OOH 自由基，而两种自由基与齐聚自由基的结合强度都大于与 PAHs 的结合强度。此外，发现 OH 和 OOH 自由基都更强烈地结合在齐聚自由基的边缘，而不是在其内部位置。结果表明，齐聚自由基可以作为 OH 和 OOH 自由基的有效清除剂，因此，这些材料可用于保护生物和非生物系统免受与这些自由基反应造成的损害。
