Molecular arrangement and photochemistry of a bolaamphiphilic anthracene derivative in Langmuir-Blodgett film

Molecular arrangement and photochemical reactions have been investigated in the Langmuir-Blodgett (LB) films of a novel bolaamphiphilic anthracene derivative (BISANS) in comparison with those of one-headed amphiphilic anthracene derivative (ANS). It has been found that ANS forms a stable monolayer at the air/water interface, while BISANS undergoes aggregation processes to form crystal film on the water surface, as evidenced from the surface pressure (pi)-area (A) isotherm, scanning electron microscopy (SEM) and X-ray diffraction (XRD) measurements. UV-VIS spectra reveal that both the H-aggregation and the J-aggregation exist in the deposited LB films of bolaamphiphilic BISANS; while only J-aggregation is formed in the LB film of ANS. The content of the H-aggregation in the LB films depends on the transfer surface pressure. The orientation of anthracyl chromophores has an effect on the photoreaction in the LB films. When both the ANS and the BISANS LB films were irradiated with UV light (365 run), photodimerization took place predominantly in nitrogen atmosphere, while photooxidation occurred preferentially in air. (C) 2001 Elsevier Science B.V. All rights reserved.