π-π stacking controlled photochromic/thermochromic properties of salicylaldehyde Schiff base in solid state

Salicylaldehyde Schiff base is a kind of typical photochromism and thermochromism system with aggregation-induced emission (AIE) characteristic. In this work, three salicylaldehyde Schiff base derivatives of 1–3 were synthesized, which showed similar emissions but different photochromic/thermochromic properties in solid state. Only compound 1 exhibited reversible photo- and thermo-responsive performances in solid state according to the enol-keto tautomerism upon UV light irradiation and heating. Mechanism study showed that these different photochromic/thermochromic properties were controlled by the π-π stacking structure of adjacent molecules. This work provided a new perspective to understand the photochromic/thermochromic mechanism of salicylaldehyde Schiff base in solid state.