The NICS X-scans for 1-3 showed a plateau of maximum diatropicity extending over the two five-membered rings, with the shallow minima above the bonds originating from σ-effect contaminations. This feature is again consistent with an induced ring current over the ellipsoidal pentalenide perimeter, as seen in the ACID maps. The X-scans should however allow to differentiate whether this was due to a global current over the entire pentalenide system, or the result of superposition of local ring currents in the two fused cyclopentadienyl subunits. If the latter was the case, the absence of a significant current density at the transannular C-C bond, which is most pronounced in the ACID plot of 1, would be the result of a net cancelation of two counter-currents across this linkage. To answer this question, the NICS X values of 1 and the parental cyclopentadienyl anion at the same position were compared. In the case of a superposition of two local Cp -ring currents, the NICS values at 1.7 Å above the central C-C bridge of 1 (-21.1 ppm) should be approximately twice the value for the cyclopentadienyl anion at the same Z height and at 1 Å from its ring centre (-12.8 ppm), which is equivalent to the distance between the middle of one pentalenide ring and the transannular C 3' -C 6' bond in 1. As this was not the case, it leads to the conclusion that in 1 no local cyclopentadienyl ring currents exist, and that the overall cyclic current is indeed due to an overall pentalenide circuit. This situation prevailed in compound 2, where the reference 1,3diphenylcyclopentadienide (1,3-Ph2Cp -) had a NICS X value of -12.0 ppm at 1 Å and 2 had a NICS value of -14.1 ppm at the C 3' -C 6' bridge (Figure ).