Comparative study on the inclusion behavior between meso-tetrakis(4-N-ethylpyridiniurmyl)porphyrin and β-cyclodextrin derivatives

Abstract 5,10,15,20-Tetrakis(4- N -ethylpyridiniurmyl)porphyrin (TEPyP) formed 1:1 stoichiometry inclusion complexes with β-cyclodextrin (β-CD) and its derivatives including hydroxypropyl-β-cyclodextrin (HP-β-CD), sulfobutylether-β-cyclodextrin (SBE-β-CD) in basic aqueous solution. The supramolecular system was investigated by the methods of fluorescence, UV–vis absorption spectroscopy, nuclear magnetic resonance (NMR) technique. The inclusion ability of cyclodextrins exhibited remarkable difference for β-CD, HP-β-CD and SBE-β-CD. Association constants as high as K =1.1×10 4  M −1 in the case of HP-β-CD/TEPyP and 2.0×10 5  M −1 in the case of SBE-β-CD/TEPyP complexes were determined, whereas a lower value ( K =550 M −1 ) was given in the case of β-CD/TEPyP. The results showed that hydrogen bonding and charge attraction play important roles in the processes of host–guest interaction. The interaction mechanism of inclusion processes could be explained by the analysis of NMR spectroscopy. The supramolecular assembly was formed. β-CD and HP-β-CD approached from the primary face of cavities of CDs.