Cho Daeheum, Ko Kyoung Chul, Lee Jin Yong
Department of Chemistry, Sungkyunkwan University , Suwon 440-746, Korea.
J Phys Chem A. 2014 Jul 10;118(27):5112-21. doi: 10.1021/jp5046639. Epub 2014 Jun 25.
The intramolecular magnetic coupling constant (J) values of sets of diradicals linked to bis-DTDA, OVER, and NN radicals (DTDA, OVER, and NN groups) through an aromatic coupler were studied by unrestricted density functional theory calculations (UB3LYP/6-311++G(d,p)). Among 15 aromatic couplers, 9 compounds with an odd number of carbon atoms along its spin coupling path were found to interact ferromagnetically upon coupling with bisradicals while the other 6 couplers with an even number of carbon atoms along its spin coupling path give rise to antiferromagnetic coupling. The overall trends in the strength of magnetic interactions of aromatic couplers were preserved for DTDA, OVER, and NN groups so that the trend can be utilized as an index for the magnetic strength of a given coupler. It was found that the differences in the nucleus-independent chemical shift (NICS), bond order of connecting bonds, and Mulliken atomic spin density at connected atoms between triplet and BS states are closely related to the intramolecular magnetic behavior. 2,4- and 2,5-phosphole couplers exhibit the strongest intramolecular ferromagnetic and antiferromagnetic interactions among 15 aromatic couplers when linked to diverse bisradicals.
通过无限制密度泛函理论计算（UB3LYP/6-311++G(d,p)）研究了通过芳香族耦合剂与双DTDA、OVER和NN自由基（DTDA、OVER和NN基团）相连的双自由基组的分子内磁耦合常数（J）值。在15种芳香族耦合剂中，发现9种沿着其自旋耦合路径具有奇数个碳原子的化合物在与双自由基耦合时发生铁磁相互作用，而其他6种沿着其自旋耦合路径具有偶数个碳原子的耦合剂则产生反铁磁耦合。对于DTDA、OVER和NN基团，芳香族耦合剂的磁相互作用强度的总体趋势得以保留，因此该趋势可作为给定耦合剂磁强度的指标。研究发现，三线态和BS态之间在与相连原子处的核独立化学位移（NICS）、连接键的键级以及Mulliken原子自旋密度的差异与分子内磁行为密切相关。当与不同的双自由基相连时，2,4-和2,5-磷光体耦合剂在15种芳香族耦合剂中表现出最强的分子内铁磁和反铁磁相互作用。
