Transformation, memorization and amplification of chirality in cationic Co(III) complex-porphyrin aggregates

Lambda-and Delta-enantiomers of cis-[CoBr(NH3)(en)(2)]Br-2 were obtained by absolute asymmetric synthesis. The interactions between the achiral 5,10,15,20-tetrakis(4-sulfonatophenyl) porphyrin (TPPS) and two chiral cationic Co(III) complexes were studied by UV-vis spectroscopy, circular dichroism (CD), fluorescence spectroscopy and atomic force microscopy (AFM). It was found that the cationic Co( III) complexes can induce the formation of chiral porphyrin J-aggregates, that the metal-centered chirality can be transferred to the J-aggregates, and that the chirality was able to be memorized and amplified in the porphyrin J-aggregates. Therefore, this should be a good chiral model for understanding similar processes in physical and biological systems.