Dipole moments were measured for a series of substituted benzenes, biphenyls, terphenyls, C-monoaryl- and C,C'-diaryl-p-carboranes. The magnitude of the dipole moment reflects the ability of the "bridge" to transmit electronic effects between donor and acceptor groups.
Thus, whilst the 1,4-phenylene bridges allow moderate electronic interactions between the remote groups, the p-carboranediyl unit is less efficient as a conduit for electronic effects. A theoretical analysis was carried out at B3LYP/6-31G* and its results agree with experimental findings