Aggregation processes and photophysical properties of chlorophyll a in aqueous solutions modulated by the presence of cyclodextrins

In the present paper we report the preliminary results on the behaviour of chlorophyll a (Chl a), the main photosynthetic amphiphilic pigment of green plants, in water and aqueous solutions of cyclodextrins (alpha-cyclodextrin, hydroxypropyl-beta-cyclodextrin, heptakis(2,6-di-O-methyl)-beta-cyclodextrin and hydroxypropyl-gamma-cyclodextrin). In particular our study was aimed to understand the influence of CDs on solubility and aggregation of Chl a in water and to get information on the interactions between different cyclodextrins and the pigment. The role played by different CDs in affecting the photoactivity of the chlorophyll, with particular attention to the quantum yield of the singlet oxygen production, has been also discussed. The study was carried out by using different spectroscopic (UV-Vis, fluorescence, circular dichroism, time resolved absorption and luminescence) and calorimetric (ITC) techniques.