Using P we investigated its interaction with CSA as a chiral guest, using UV-Vis and CD-spectroscopy. UV-vis titration with 302 eq. of (R)-CSA to P (protonated with 20 eq. of TFA) showed a bathochromic shift of a newly developed Soret-band at 468 nm followed by the appearance of two new Q-bands at 614 and 672 nm indicating a strong binding event (Ka1 = 4.6  10 5 ; Ka2 = 7.3  10 3 ) (Figure and). The UV-vis spectral lines of P/(R)-CSA correspond well with the previously reported α4-P interactions observed with bisulfate. In the case of ECD spectroscopy, the hexacationic porphyrin P and its complex with (R/S)-CSA are ECD silent. However, the complexes formed with enantiomerically pure (S)-or (R)-CSA exhibit induced ECD spectra in the region of the porphyrin Soret absorption. The ECD profiles consist of two bisignate Cotton effects at 462 and 477 nm in chloroform, and at 450 and 464 nm in dichloromethane (see Figure and 3b, S3 and S5). These two solvents were chosen as the most conventionally used solvents for ECD measurements of porphyrins, which do not interact with the studied complex and do not affect the ECD spectra due to solvent-solute interactions.