Conformational Flexibility in Dodecasubstituted Porphyrins

Abstract

In contrast to regular porphyrins, dodecasubstituted porphyrins have not so far been demonstrated to possess a high degree of conformational flexibility. To determine if this is a general feature of dodecasubstituted porphyrins, we have undertaken an investigation of the conformational properties of the dodecaarylporphyrins 4-6. We show herein that crystal structures of these porphyrins provide ample evidence of the significant conformational flexibility that can be observed for dodecasubstituted porphyrins; the structures we report include the first highly ruffled dodecasubstituted porphyrin, the first examples of multiple conformations in a single dodecasubstituted porphyrin, and the first `wave` core structure of a dodecasubstituted porphyrin, which is also the most nonplanar wave structure reported to date for any porphyrin. The structure reported herein for nickel(II) complexes and metal-free porphyrins 4-6 clearly indicate that these porphyrins possess a higher degree of conformational flexibility than has previously been observed for other dodecasubstituted porphyrins. 6 refs., 2 figs.