This was also reflected in the comparison of the NBO charges on the two different aryl moieties of 2 and 3, where the phenyl groups accepted slightly more charge density than the tolyl groups (-1.10 e for 2 vs. -1.05 e for 3). The same analysis allowed understanding the effect of unsymmetrical substitution patterns. In the pentalenides 9 and 10, the subunits without aryl groups in the 4,6 positions showed a higher sum of charges than their phenylated or p FPhsubstituted counterparts where the negative charge can be effectively delocalised into these substituents. This correlates with a highfield shift in the H 5 proton (both 6.06 ppm for 9 and 10) while the H 2 protons on the substituted five-membered rings were found at 7.05 ppm for 9 and at 6.92 ppm for 10, respectively. The slightly more shielded H 2 in 10 compared to that in 9 can be ascribed to the +M effect of the fluorine atoms in para-position of the p FPh substituents; hence, the π-systems of the p FPh-groups in 9 accommodate less charge than the phenyl groups in 10, resulting in a higher charge density in its pentalenide subunit. Comparing 9 with 2, the 1 H NMR shifts of H 2 in 9 were even more deshielded than in 2, which can be ascribed to the above-mentioned coplanar arrangement of the phenyl substituents with respect to the pentalenide core (0° dihedral twist compared to 30.2° for 2) that results in better conjugation and thus more effective charge distribution. This was also reflected in the absolute charge values of the aryl substituents, where one phenyl group in 2 accepted an anionic charge of -0.28 e while in 4 it accepted -0.39 e.