Complex formation between naphthalene and dimethyl-β-cyclodextrin by heating in a sealed ampoule

Abstract

An equimolar mixture of naphthalene and amorphous heptakis-(2,6-di-O-methyl)-β-cyclodextrin (DMβCD) has been heated in a sealed container at 70 °C. The naphthalene–DMβCD complex was different from the inclusion complex obtained by coprecipitation. Two types of the complex were obtained by ‘sealed-heating’ at different temperatures; heating the mixture at 60–80 °C gave a complex that showed excimer emission of naphthalene at 390 nm, whilst heating the mixture above 90 °C gave a complex that exhibited monomer emission of naphthalene at 341 nm. It was also possible to differentiate between the two forms of the complex by powder X-ray diffraction and thermal analysis.