Interaction Between Terminal Zinc–Porphyrins in a U‐Shaped Trimeric Porphyrin Array Bearing Chiral Amino Acid Tails

Abstract A U‐shaped trimeric porphyrin array with a zinc/free‐base/zinc arrangement (5ZFZ) and its derivatives were synthesized in order to investigate the interacting porphyrins in organic solvents. The porphyrin array is comprised of an αα‐atropisomeric bis(ortho‐aminophenyl)porphyrin free‐base as the template, a pair of zinc–porphyrins at the termini, achiral glycine spacers linking the porphyrins, and chiral L‐leucine derivatives attached to the template in the opposite direction of the zinc–porphyrins. 1H NMR (high‐field shifts of some pyrrole signals), UV/Vis (split Soret band), and CD spectra (exciton‐coupled Cotton effect) show the close assembly of the terminal zinc–porphyrins of 5ZFZ in CDCl3 and CH2Cl2. In contrast, the characteristic spectra for the interacting porphyrins do not appear for the trimeric array with three free‐base porphyrins (5F3) and the dimeric array with a zinc/free‐base arrangement (9ZF). (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)