The Quadrupole Moment of Substituted Cyclopentadienyl Anions

作者：Cormier Kevin W; Watt Michelle; Lewis Michael^*

来源：Journal of Physical Chemistry A, 2010, 114(43): 11708-11713.

DOI：10.1021/jp104499y

Previous work in our group on the cation binding of substituted cyclopentadienyl anions (Cp) showed the curious result that Cp traceless electric quadrupole moments (Theta(zz))re almost all positive. Probing this issue further here we show that substituted Cp Theta(zz). values are always significantly more positive than the analogous substituted benzenes. Given the nature of aromatic Theta(zz) values, this is the opposite of what would be predicted. Furthermore, we show that the quadrupole moments of Cp anions do not behave as one would expect based on Cp substitutions. Unlike the quadrupole moments of substituted benzenes, which generally become more negative with the addition of electron-donating groups and more positive with the addition of electron-withdrawing groups, Cp quadrupole moments become more positive when any substituent is added, regardless of the electron-donating/withdrawing nature of the substituent. To explain these results we propose a model where the anionic Cp pi-electron density repels the substituent electron density toward the molecular periphery and AIM calculations support this view.

• 出版日期2010-11-4