Zhou Hongwei, Wong Ning-Bew, Lau Kai-Chung, Tian Anmin, Li Wai-Kee
Department of Biology and Chemistry, City University of Hong Kong, Kowloon, Hong Kong, Faculty of Chemistry, Sichuan University, Chengdu 610064, People's Republic of China.
J Phys Chem A. 2007 Oct 4;111(39):9838-47. doi: 10.1021/jp072460l. Epub 2007 Sep 11.
In this work, the geometries, harmonic vibrational frequencies, and high-energy density material (HEDM) properties of a novel species and its six derivatives with the general formula C14N12-R6 (R = H, OH, F, CN, N3, NH2, and NO2) have been investigated at the restricted and unrestricted B3LYP/cc-pVDZ levels of theory. Natural bond orbital (NBO), natural orbital (NO), and atoms in molecules (AIM) analyses are applied to examine their electronic topologies. It is found that for the four species of R = H, CN, N3, and NO2, (1) there exist high LUMO occupation numbers, (2) there is considerable spin density congregated on the two central carbon atoms, (3) there exists through space interaction (or intramolecular interaction, which is one of the stabilizing factors of a diradicaloid) between the two central carbon atoms, (4) the distance (about 3 A) between the two central carbon atoms (as the apexes of two trigonal pyramids with their bases facing each other) is suitable and favorable for diradical formation. All the results support that these four species are diradicals or diradicaloids. Furthermore, the appreciable singlet-triplet energy gaps indicate that these four diradicals tend to have a singlet ground state. There is a moderate HOMO-LUMO gap (on the order of 1.5 to 2.1 eV) for these four species. These four singlet diradicals may be novel organic semiconductor materials or nonlinear optical materials. On the other hand, the remaining three species, with R = OH, F, and NH2, are not diradicaloids.
在本工作中，在受限和非受限的B3LYP/cc-pVDZ理论水平下，研究了一种通式为C14N12-R6（R = H、OH、F、CN、N3、NH2和NO2）的新型物种及其六种衍生物的几何结构、谐振动频率和高能量密度材料（HEDM）性质。应用自然键轨道（NBO）、自然轨道（NO）和分子中的原子（AIM）分析来研究它们的电子拓扑结构。结果发现，对于R = H、CN、N3和NO2这四种物种，（1）存在较高的LUMO占据数，（2）有相当多的自旋密度聚集在两个中心碳原子上，（3）两个中心碳原子之间存在空间相互作用（或分子内相互作用，这是双自由基oid的稳定因素之一），（4）两个中心碳原子（作为两个底面相对的三角锥的顶点）之间的距离（约3 Å）适合且有利于双自由基的形成。所有结果都支持这四种物种是双自由基或双自由基oid。此外，可观的单重态-三重态能隙表明这四种双自由基倾向于具有单重态基态。这四种物种具有适度的HOMO-LUMO能隙（在1.5至2.1 eV量级）。这四种单重态双自由基可能是新型有机半导体材料或非线性光学材料。另一方面，其余三种R = OH、F和NH2的物种不是双自由基oid。
