Aggregation of an anionic porphyrin with chiral metal complexes and the competitive binding influences of a surfactant and a polyelectrolyte

Abstract

The non-covalent interactions of chiral metal complexes with the achiral 5,10,15,20-tetrakis (4-sulonatophenyl) porphyrin (H₄TTPS²⁻) have been investigated by UV-vis and circular dichroism (CD) spectra. The results show that under acidic environments, only the chiral complex cations ([CoBr(NH₃)(en)₂]⁺, [Co(en)₃]³⁺, [Ru(phen)₃]²⁺) could interact with H₄TTPS²⁻ to form chiral aggregates, accompanied with the metal-centered chirality information transferred to the formed J-aggregates. However, the chiral complex anion ([Co(edta)]⁻) does not cause the self-assembly process. The competitive binding interactions between an achiral water-soluble cationic surfactant (N-hexadecyltrimethyl ammonium chloride, CTAC) and a cationic polyelectrolyte (polyallylamine, PAA) with the chiral metal complex H₄TTPS²⁻ J-aggregates, respectively, were also investigated. It was found that chiral-symmetry-breaking phenomena occur in the cationic surfactant induced event. In the case of a cationic polyelectrolyte, it could change the conformational flexibility of the H₄TTPS²⁻ aggregates. These results may lead us to understand the possible mechanism of the supramolecular self-assembly process by the non-covalent interactions.