Supramolecular Chirality and Chiral Inversion of Tetraphenylsulfonato Porphyrin Assemblies on Optically Active Polylysine

Abstract

The self-assembly and induced supramolecular chirality of a dianionic meso-tetraphenylsulfonato porphyrin (TPPS) on the optically active polylysine has been investigated. Our research has confirmed that in the presence of poly(l-lysine) (PLL) or poly(d-lysine) (PDL), TPPS could form both H and J aggregates and the exciton type Cotton effect was induced in the corresponding absorption bands of H and J-aggregates. We have further revealed that the induced chirality of the H-band always followed the chirality of PLL or PDL, while the sign of the exciton couplet in the J-band could be the same as or opposite to that of the H-band depending on the mixing sequence and the ratio of PLL or PDL to TPPS (P/T ratio). At a P/T ratio less than 4, both the J and H aggregates showed the same symbolic CD signal. At a P/T ratio larger than 4, the opposite sign of the exciton couplet was observed for H and J-bands when TPPS was added into PLL, while the same sign was obtained when PLL was added into TPPS. Interestingly, the J-band with the same sign as that of the H-band can be inverted into the opposite sign under heating. A mechanism relating to the dynamic and thermodynamic formation of the chiral aggregates in the presence of PLL or PDL was proposed.