University of Helsinki, Department of Chemistry, P.O. Box 55, FIN-00014, Finland.
Phys Chem Chem Phys. 2011 Dec 14;13(46):20659-65. doi: 10.1039/c1cp21935a. Epub 2011 Sep 30.
Magnetically induced current densities and strengths of currents passing through selected bonds have been calculated for monophosphorous [28]hexaphyrin ((PO)[28]hp) and for bisphosphorous [30]hexaphyrin ((PO)(2)[30]hp) at the density functional theory level using our gauge-including magnetically induced current (GIMIC) approach. The current-density calculations yield quantitative information about electron-delocalization pathways and aromatic properties of singly Möbius twisted hexaphyrins. The calculations confirm that (PO)[28]hp sustains a strong diatropic ring current (susceptibility) of 15 nA T(-1) and can be considered aromatic, whereas (PO)(2)[30]hp is antiaromatic as it sustains a paratropic ring current of -10 nA T(-1). Numerical integration of the current density passing through selected bonds shows that the current is generally split at the pyrroles into an outer and an inner pathway. For the pyrrole with the NH moiety pointing outwards, the diatropic ring current of (PO)[28]hp takes the outer route across the NH unit, whereas for (PO)(2)[30]hp, the paratropic ring current passes through the inner C(β)=C(β) double bond. The main diatropic ring current of (PO)[28]hp generally prefers the outer routes at the pyrroles, whereas the paratropic ring current of (PO)(2)[30]hp prefers the inner ones. In some cases, the ring current is rather equally split along the two pathways at the pyrroles. The calculated ring-current pathways do not agree with those deduced from measured (1)H NMR chemical shifts.
在密度泛函理论水平上，使用我们的包含磁场诱导电流的规范（GIMIC）方法，计算了单磷[28]六卟啉((PO)[28]hp)和双磷[30]六卟啉((PO)(2)[30]hp)中通过选定键的感应电流密度和电流强度。电流密度的计算提供了关于单莫比乌斯扭曲六卟啉电子离域途径和芳香性质的定量信息。计算结果证实(PO)[28]hp 维持着 15 nA T(-1)的强顺磁环电流（磁化率），可以被认为是芳香的，而(PO)(2)[30]hp 是反芳香的，因为它维持着-10 nA T(-1)的反磁环电流。通过选定键的电流密度的数值积分表明，电流通常在吡咯中分裂成外部和内部途径。对于 NH 部分向外指向的吡咯，(PO)[28]hp 的顺磁环电流通过 NH 单元走外部途径，而对于(PO)(2)[30]hp，反磁环电流则通过内部 C(β)=C(β)双键走内部途径。(PO)[28]hp 的主要顺磁环电流通常在吡咯中更喜欢走外部途径，而(PO)(2)[30]hp 的反磁环电流则更喜欢走内部途径。在某些情况下，环电流在吡咯中沿两条途径相当均匀地分裂。计算出的环电流途径与从测量的(1)H NMR 化学位移推断出的途径不一致。
