Study on the inclusion behavior between meso-tetrakis[4-(3-pyridiniumpropoxy)phenyl]prophyrin tetrakisbromide and β-cyclodextrin derivatives in aqueous solution

The interaction of a cationic water-soluble porphyrin, 5,10,15,20-tetrakis[4-(3-pyridiniumpropoxy)phenyl]prophyrin tetrakisbromide (TPPOC3Py), with β-CD and HP-β-CD in aqueous solution has been studied by UV–vis, 1H NMR, 2D-NOESY and MALDI-TOF MS, and it reveals that a stable 1:1 inclusion complex between TPPOC3Py and HP-β-CD or β-CD has formed, in which one of the meso substituents of porphyrin ring has deeply penetrated through the cavity of HP-β-CD from secondary face. The inclusion constants of the complexes of TPPOC3Py–β-CD and TPPOC3Py–HP-β-CD are (1.6 ± 0.2) × 103 M−1 and (8.9 ± 0.4) × 104 M−1, respectively.