Effect of proton ion concentration on the supramolecular interaction between phenoxazine and ?-cyclodextrin

In aqueous and /3-cyclodextrin ( /3-CD) media, the spectral characteristics of phenoxazine (POZ) have been in-vestigated by means of absorption, steady-state, and time-resolved fluorescence techniques. The stoichiometric ratio of the mono-cationic and neutral forms of POZ in the /3-CD medium is found to be 1:1. Inclusion complexes of POZ with /3-CD has been confirmed in the solid state by the analysis of characterization techniques, such as Fourier transfer infrared spectroscopy (FT-IR), and proton nuclear magnetic resonance spectroscopy, POZ has a significant difference in the ground and excited-state pKa values in aqueous and /3-CD media. As a result, the amino group of the molecule, POZ is affected by the complexation process, i.e., it lies within the cavity of /3-CD. It is clear from the shape and dimensions of /3-CD that the POZ molecule cannot fit completely inside the cavity. As a result, 2POZ's overall height is 10.6 angstrom, while /3-CD's is just 7.8 angstrom. As per the discussion, the structure of the 1:1 complex has also been proposed.