Study on the supramolecular system of 5-(p-hydroxyphenyl)-10,15,20-tris-(4-chlorophenyl)porphyrin with cyclodextrins and its analytical characteristics

The supramolecular systems of 5-(p-hydroxyphenyl)-10,15,20-tris-(4-chlorophenyl)porphyrin (p-HTClPP) with β-cyclodextrin (β-CD), heptakis(2,3,6-tri-O-methyl)-β-CD (TM-β-CD), carboxymethyl-β-cyclodextrin (CM-β-CD) and sulfurbutylether-β-CD (SBE-β-CD) have been investigated by means of absorption, fluorescence and 1H NMR spectroscopy. The formation of inclusion complexes has been confirmed on the base of changes of spectroscopy properties. “The double reciprocal method” has been used to determine the stoichiometry and the inclusion constants of p-HTClPP with the four cyclodextrins (CDs). The results show that p-HTClPP can form 1:1 inclusion complexes with the four CDs. Compared with parent native β-CD, the inclusion abilities of modified β-CDs with p-HTClPP are stronger. It indicates that the hydrophobic effect plays an important role in the inclusion procedure. The mechanism of inclusion interaction was examined by 1H NMR technique. During the study of p-HTClPP–TM-β-CD supramolecular complex, an efficient enhancement of fluorescence intensity was observed. Based on this phenomenon, fluorometric method for the determination of p-HTClPP was developed. The relationship between fluorescence intensity and the concentration of p-HTClPP is linear from 1.0 × 10−9 to 7.0 × 10−6 mol L−1. The limit of detection is 8.3 × 10−10 mol L−1 and the relative standard deviation (R.S.D.) is 1.3% (n = 8). This research will provide useful information for further application of p-HTClPP.