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

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. 1 H 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 CDCl 3 and CH 2 Cl 2 . In contrast, the characteristic spectra for the interacting porphyrins do not appear for the trimeric array with three free‐base porphyrins ( 5F 3 ) and the dimeric array with a zinc/free‐base arrangement ( 9ZF ). (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)