Cu2+ induced charge transfer switch by choosing the right cyclodextrin environment

Compounds like trans-2-[4-(dimethylamino)styryl]benzothiazole (DMASBT) take part in compound induced cyclodextrin (CD) nanotubular suprastructure formation. The molecule undergoes differential encapsulation inside the CD cavities of different sizes and hence experience restricted freedom in its movement. DMASBT is capable of undergoing intramolecular charge transfer in the excited state in polar media. This physical phenomenon has been exploited to study the Cu2+ sensing capability of encapsulated DMASBT. The intramolecular charge transfer is found to get switched on employment of Cu2+ ions with the proper choice of cyclodextrin molecules for encapsulation. The differential encapsulation of the compound inside the CD cavities is held to be responsible for this behavior. The complexation takes place in the ground state and because of the difference in charge density on the ligating centers: the system is capable to show a switching behavior in the twisted intramolecular charge transfer (TICT) emission of the guest molecule inside the various cyclodextrin moieties. (C) 2010 Elsevier B.V. All rights reserved.