STUDIES OF AN INCLUSION COMPLEX OF A REDOX-ACTIVE BARBITURATE WITH BETA-CYCLODEXTRIN

The effects of beta-cyclodextrin (beta-CD) on the spectral properties and electrochemical behaviour of barbitone sodium were studied using electrochemical and optical techniques. The apparent changes in the UV-visible absorption spectrum and the fluorescence quenching of the barbiturate upon addition of beta-CD afford clear evidence of the inclusion complex formation by beta-CD in aqueous solutions. The redox activity of barbitone sodium in both the absence and presence of beta-CD was assessed by an electrochemical method in 0.05 M potassium nitrate-nitric acid (pH 1.8) solution. While the complexation reaction remains in equilibrium, the apparent formation constant of the inclusion complex could be obtained by either spectral or electrochemical methods. Quantitative evaluation of the data gave 326 l mol(-1) under equilibrium conditions at 20 degrees C. Possible conclusions are discussed on the basis of environmental changes around the barbiturate molecules on inclusion.