Molecular J-aggregation for the Langmuir-Blodgett film of a novel tripodal dye

Abstract

We investigated the arrangement of a tripodal dye. N-1,N-3,N-5-tris(4-(5-(3,4,5-tridodecyloxyphenyl)-1,3,4-oxadiazol-2-yl)phenyl)benzene-1,3,5-tricarboxamide, A3O-3 (amide linkage), at the air-water interface by the Langmuir-Blodgett technique. The surface pressure (Pi) vs. surface area (A) isotherm for A3O-3 showed a sharp transition at 200 angstrom(2)/molecule. AT-IR and UV-visible spectrophotometry were employed to study the self-assembled structure of A3O-3 multilayers on the substrate. Comparisons with theoretical calculations of the molecular and extrapolated areas of the Pi-A isotherm revealed that a change in the molecular arrangement of the A3O-3 monolayer took place under conditions of sharply increasing surface pressure. AT-IR data showed no hydrogen-bonding at high pressure and also demonstrated that the stability of the monolayer is due to pi-pi interactions. UV data displayed a maximum red shift as the surface pressure increased, which suggests that J-aggregation was initiated at the monolayer interface.