Enhanced AIE and different stimuli-responses in red fluorescent (1,3-dimethyl)barbituric acid-functionalized anthracenes

Abstract

Two structurally simple and red light-emitting AIE luminogens, (1,3-dimethyl)barbituric acid-functionalized anthracenes (B-A and DMB-A), were designed and synthesized. In comparison with DMB-A, B-A shows strikingly enhanced AIE as well as superior thermal stability (T_d, 328.5 °C vs. 280.2 °C). Moreover, distinguishable behaviors of the two red luminogens to stimuli such as (1) dissolution (in 1,4-dioxane), then solidification via removing the solvent in vacuo at 50 °C, (2) thermal treatment following stimuli-I and (3) mechanical grinding were observed. In particular, reversible switching of colours (orange ↔ red), accompanied by a fluorescence shift (Δλ_em ≈ 36 nm) was achieved by repeatedly applying stimuli (I) and (II) on luminogen B-A, whereas almost no change of luminogen DMB-A was found under the same conditions. A mechanism of solvent molecule assisted B-A molecular packing changes was proposed to illustrate the origin of B-A's chromic phenomenon.