CYCLODEXTRIN-INDUCED ASYMMETRY OF ACHIRAL NITROGEN-HETEROCYCLES

Recent studies investigating the nature of fluorescence quenching effects of beta-cyclodextrin (beta-CDx) upon various nitrogen heterocycles suggest the importance of the position and number of nitrogen heteroatoms within the guest molecule. The sensitivity of molecules such as acridine (ACR) and phenazine (PHEN) toward the microenvironment provided by cyclodextrins appears to originate with the heteroatom. Quenching has also been observed for ACR and PHEN in the presence of alpha-and gamma-CDx, although it is less extensive than in the beta-CDx system. Induced circular dichroism (ICD) measurements arc able to provide a more reliable estimate of apparent formation constants for the beta-CDx systems since complex formation is a prerequisite for guest-induced symmetry in the cases discussed here. Fluorescence measurements were used to assess the association constants of the alpha- and gamma-CDx with PHEN and ACR. The influence of size compatibility between guest and host and the orientation of the guest within the CDx molecule are also evaluated.