Solvatochromism, acidochromism and aggregation-induced emission of propeller-shaped spiroborates

Abstract

Propeller-shaped pyridyl-enolato-catecholate/-salicyl spiroborates (Sborepy1–6) were synthesized. The complexes Sborepy3–6 show weak emission in fluid solution and aggregation-induced emission enhancement in the aggregation state with large Stokes shifts of 4025–5237 cm⁻¹. Moreover, intense solid-state emissions with high Φ_f ranging from 25% to 37% were observed for Sborepy3–6 owing to the weak intermolecular interactions in their solid-state. The AIE and intense solid-state emission have been revealed via the X-ray diffraction analysis and theoretical calculations. Furthermore, the solvatochromism in the solution state and the potential application as a fluorescent acidic vapour sensor in the solid state of Sborepy3 and Sborepy6 were also demonstrated.