Table 1: Optimized bond distances (in Å), NICS values (in ppm) at different positionsa, and electron configurations of the lowest-energy ( ) and ( ) clusters.

Cluster NICSb Electron configuration
0.0 Å0.5 Å1.0 Å1.5 Å2.0 Å3.0 Å

2.722
2.858
2.721−259.6
(−236.1)
−183.7
(−177.4)
−50.7
(−47.3)
−25.2
(−24.4)
−14.1
(−15.7)
−8.5
(−10.6)
( )2( )4( )2( )2
( )4( )2( )4( )4
( )2( )4( )4( )4
( )2( )2( )4( )4
( )2( )4( )4

2.611
2.644
2.647
2.855
2.814
2.942
−296.4
(−277.1)
−199.0
(−196.4)
−61.3
(−60.8)
−36.3
(−37.7)
−25.8
(−28.0)
−18.0
(−19.4)
(1a1)2(1b2)2(1e)4(2a1)2
(2b2)2(2e)4(1b1)2(3e)4
(3a1)2(3b2)2(4a1)2(4e)4
(1a2)2(2b1)2(4b2)2(5e)4
(5a1)2(5b2)2(6a1)2(6e)4
(6b2)2(7e)4(3b1)2(7a1)2
(8e)4(2a2)2

aNICS values were computed at the GIAO-B3LYP/LanL2DZ//B3LYP/LanL2DZ level, based on the positions located on the radial connecting the center site (see Figure 1).
bNICS values in parentheses were obtained from the GIAO-B3LYP/cc-pVTZ-PP//B3LYP/LanL2DZ calculations.