Self‐Assembly and Chiroptical Properties of Chiral Dendrimers Consisting of a Hamilton Receptor Substituted Porphyrin and Depsipeptide Cyanurates

Abstract

AbstractThe synthesis and characterisation of a new type of porphyrin‐based tetrakis(Hamilton receptor) 1 is presented and the complexation of 1 with the chiral depsipeptide dendrons 7–12, with cyanuric acid functionalities as their focal points, is reported. The resulting first‐ to third‐generation chiral supramolecular dendrimers 13–18 were characterised by NMR, UV/Vis and CD spectroscopy. Chirality transfer from the depsipeptide dendrons to the porphyrin core was demonstrated by CD spectroscopy in the case of the second‐ and third‐generation complexes 15–18, whereas no chirality transfer and hence no diastereoselective formation of a chiral superstructure could be determined in the case of the first‐generation systems. The intensities of the complexes’ CD absorptions in the porphyrin region are inversely proportional to the size of the dendrons, pointing to a size‐dependent cooperativity of the fourfold complexation of the dendrons with the more effective binding of the second‐generation dendrons 9 and 10 relative to their bulkier third‐generation counterparts 11 and 12. Pronounced cooperativity during the formation of the second‐generation 1:L4 complexes (L = 9, 10) is considered to be the reason for the diastereoselective formation of a preferred chiral conformation of the Hamilton receptor 1 in the complexes 15 and 16. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)