Department of Chemistry, University of Sheffield, Sheffield, S3 7HF, United Kingdom.
J Phys Chem A. 2010 Oct 7;114(39):10742-9. doi: 10.1021/jp106697j.
Aromatic benzene and nonaromatic borazine can be modeled as the end-points of a continuous process evolving through intermediate systems with fractional nuclear charges. Current-density maps show a smooth, linear progression in which the global diatropic π ring current weakens as localized diatropic lone-pair currents grow with the increase in charge difference. In contrast, the progression from antiaromatic (planarized) cyclooctatetraene to nonaromatic borazocine shows an initially persistent paratropic ring current with a sharper transition to the localized diatropic system. The different behaviors of aromatic and antiaromatic systems stem from the different orbital origins of diatropic and paratropic ring current, and both can be rationalized in terms of arguments based on π distortivity and electronegativity.
芳香苯和非芳香硼氮烷可以被模拟为通过具有分数核电荷的中间系统演变的连续过程的端点。电流密度图显示了一种平滑的线性进展，其中全局顺磁 π 环电流随着电荷差的增加而减弱，而局部顺磁孤对电流增强。相比之下，从反芳香（平面化）环辛四烯到非芳香硼氮杂环的进展显示出初始持续的反磁环电流，然后更急剧地转变为局部顺磁系统。芳香和反芳香系统的不同行为源于顺磁和反磁环电流的不同轨道起源，并且都可以根据基于π扭曲度和电负性的论点来合理化。
