Competitive processes of a chromophore modified α-cyclodextrin in the presence of a fluorescence polarity sensitive probe

Steady-state fluorescence, time-resolved fluorescence, molecular mechanics (MM) and molecular dynamics (MD) were employed to study the thermodynamics of the complexation of 2I, 3I-O-(o-xylylene)-α-cyclodextrin (XαCD), which is also capable of self-aggregation, with a fluorescent polarity sensitive probe, the 2-naphthalenecarboxylate (2MN), in aqueous solution. Dimerization and inclusion constants, as well as the thermodynamics parameters accompanying both processes were obtained. We also used MM and MD to investigate the conformational behavior for the isolated XαCD, the dimerization and inclusion processes and the geometry of the complexes and driving forces responsible for their formation. The results were compared with those obtained for other α-cyclodextrins in order to establish relationships between the dimer and complex structures and the thermodynamics of both processes.