AIE-active multicolor tunable luminogens: simultaneous mechanochromism and acidochromism with high contrast beyond 100 nm

The development of intelligent luminescent materials, particularly those exhibiting high-contrast (Δλem,max > 100 nm) and multicolor mechanochromic luminescent (MCL) characteristics, is highly desirable but a formidable challenge. In this work, we designed three luminogens with aggregation-induced emission (AIE) features, namely 7PTP-BPXZ, 5PTP-BPXZ and 5,7PTP-BPXZ. The synergistic effect between the folded conformation of the benzo[a]phenoxazine fragment and various intermolecular non-covalent interactions is beneficial for multicolor tunable emission upon external stimuli. Impressively, 7PTP-BPXZ and 5PTP-BPXZ displayed reversible tricolor MCL behavior with high contrast (Δλem,max, 114 nm and 137 nm, respectively). Furthermore, 7PTP-BPXZ possessed acidochromic function with Δλem,max of 132 nm. This is the first report of single-component small organic molecules featuring both multicolor and high-contrast beyond 100 nm mechanochromism and acidochromism.