Cation-induced self-assembly of an amphiphilic perylene diimide derivative in solution and Langmuir-Blodgett films

A novel amphiphilic perylenetetracarboxylic diimide (PDI) derivative, N-(4'-benzo-15-crown-5-ether)-N-hexyl-1,7-di(4-tert-butyl-phenoxy)peryle n-3,4,9,10-tetracarboxylic diimide (15C5PDI), has been synthesized and characterized. Dimerization of 15C5PDI is induced in CHCl3 solution with the present of K+, resulting in the formation of the slipped co-facial J-aggregates, as revealed by absorption and fluorescence spectroscopies. Analysis of the surface pressure-area (pi-A) isotherms and spectral change for the monolayer formed at the air/water interface, disclosed that 15C5PDI molecules adopted the H-type aggregation mode with a face-to-face configuration and edge-on orientation on both the surface of pure water and K+ aqueous solution. Consequently, a particularly interesting fluorescence emission change from ``switch-on'' to ``switch-off'' could be observed upon aggregation that was accompanied by a transformation from strongly fluorescent J-type into non-fluorescent H-type packing of the 15C5PDI dyes. Depending mainly on the coordination bonding between 15-crown-5-ether groups and K+ ions, one dimensional nanofibrils formed on the surface of the K+ aqueous solution with a more closely arrangement of 15C5PDI molecules relative to those on pure water subphase revealed by the pi-A isotherms and atomic force microscopy (AFM) images. X-ray diffraction studies indicate that the film crystallinity and general molecular order in the Langmuir-Blodgett (LB) films deposited from the KCl solution are improved effectively in comparison with those from pure water subphase. Furthermore, the conductivity of the LB films prepared in K+ solution is more than ca. 1 order of magnitude higher than those from water. (C) 2014 Elsevier B.V. All rights reserved.