A recent study on magnetically induced
currents in 10-isocorrole derivatives indicated that both the free-base
and metal-complexed forms of the unsubstituted macrocycle are homoaromatic.
Furthermore, depending on the substituents at the 10-position, the
aromatic character was found to swing between substantially homoaromatic
to substantially antihomoaromatic. Heteroisocorroles, in which the
saturated 10-position has been replaced by a heteroatom-containing
group X, are predicted to exhibit even more dramatic variations in
aromatic character, ranging from strongly aromatic (X = O, NH, PH,
and S) to strongly antiaromatic (X = BH and CO). Interestingly, the
experimentally studied X = SiMe
2
case does not appear to
sustain a significant global ring current.