Conformational analysis of novel monoaryl substituted protoporphyrins by 1D NOE, 2D NOESY and molecular modeling studies

Porphyrins 1–4 are monoaryl protoporphyrins substituted on C-5 or C-15 by a phenyl group. One- and two-dimensional nOe experiments and molecular modeling studies allowed us to find the most favorable conformations for these compounds. In the four porphyrins, the exocyclic phenyl group adopts a non-coplanar disposition relative to the plane of the macrocycle and this is reflected in the ID nOe difference and 2D NOESY results. In porphyrins 1 and 3 the macrocycle is nearly planar while nonplanar saddle conformations were obtained for porphyrins 2 and 4.