Study on the inclusion interaction of p-sulfonated calix[n]arenes with Vitamin K3 using methylene blue as a spectral probe

The characteristics of host–guest complexation between p-sulfonated calix[n]arene (SCnA, n = 4, 6) and Vitamin K3 (VK3) were investigated by fluorescence spectrometry and absorption spectrometry using methylene blue (MB) as a probe. Interaction with MB and SCnA led to an obvious decrease in fluorescence intensity of MB, accompanying with shifts of emission peaks. Absorption peaks also showed interesting changes; however, when VK3 was added, fluorescence intensity and absorbance recovered and a slight and slow red shift was observed. The obtained results showed that the inclusion ability of p-sulphonated calix[n]arenes towards VK3 was the order: p-sulphonated calix[6]arene (SC6A) > p-sulphonated calix[4]arene (SC4A). Relative mechanism was proposed to explain the inclusion process.