School of Chemistry and Chemical Engineering, Shandong University, Jinan, 250100, People's Republic of China.
Org Biomol Chem. 2016 Jan 14;14(2):542-555. doi: 10.1039/c5ob01992c.
In this work, we computationally design radical nucleobases which possess improved electronic properties, especially diradical properties through introducing a cyclopentadiene radical. We predict that the detailed electromagnetic features of base assemblies are based on the orientation of the extra five-membered cyclopentadiene ring. Broken symmetry DFT calculations take into account the relevant structures and properties. Our results reveal that both the radicalized DNA bases and the base pairs formed when they combine with their counterparts remain stable and display larger spin delocalization. The mode of embedding the cyclopentadiene free radical in the structures has some influence on the degree of π-conjugation, which results in various diradical characteristics. Single-layered radical base pairs all have an open-shell singlet ground state, but the energy difference between singlet and triplet is not significant. For two-layered radical base pairs, the situation is more complex. All of them have an open-shell state as their ground state, including an open-shell singlet state and an open-shell triplet state. That is, the majority of radical base pairs possess anti-ferromagnetic or ferromagnetic characteristics. We present here a more in-depth discussion and analyses to study the magnetic characteristics of radical bases and base pairs. As an important factor, two-layered radical base pairs also have been carefully analyzed. We hope that all the measurements and results presented here will stimulate further detailed insights into the related mechanisms in modified DNA bases and the design of better ring-expanded DNA magnetic materials.
在这项工作中，我们通过引入环戊二烯自由基来计算设计具有改进的电子性质、特别是双自由基性质的碱基。我们预测碱基组装体的详细电磁特征基于额外的五元环戊二烯环的取向。打破对称 DFT 计算考虑了相关的结构和性质。我们的结果表明，自由基化的 DNA 碱基及其与对应碱基结合形成的碱基对都保持稳定，并显示出更大的自旋离域。将环戊二烯自由基嵌入结构中的模式对π共轭的程度有一定的影响，从而导致不同的双自由基特性。单层自由基碱基对都具有开壳单线态的基态，但单重态和三重态之间的能量差并不显著。对于双层自由基碱基对，情况更为复杂。它们都具有开壳态作为基态，包括开壳单线态和开壳三重态。也就是说，大多数自由基碱基对具有反铁磁或铁磁特性。我们在这里进行了更深入的讨论和分析，以研究自由基碱基和碱基对的磁性质。作为一个重要因素，我们还仔细分析了双层自由基碱基对。我们希望这里呈现的所有测量结果和结果将进一步激发对修饰 DNA 碱基相关机制的详细研究，并设计更好的环扩展 DNA 磁性材料。
