Multistimuli-responsive materials based on a zinc(ii) complex with high-contrast and multicolor switching

Abstract

The development of stimulus-responsive luminescent materials, especially those based on a single compound exhibiting multicolor and high-contrast (Δλ_em ≥ 100 nm) chromic properties, is a critical challenge. In this work, we synthesized and characterized a zinc(II) complex (1). As expected, 1 displays aggregation-induced emission enhancement (AIEE) in THF/H₂O mixtures, and remarkable multicolor switching under external stimuli in the solid state. Complex 1 shows reversible mechanochromic luminescence behavior with a large wavelength shift (Δλ_em = 100 nm) during the grinding–fuming cycles, due to the phase transformation between the crystalline and amorphous states. More impressively, 1 exhibits obvious acidochromic properties (Δλ_em = 130 nm) which originate from the adsorption of vapor and a gas–solid reaction on the crystal surface. Furthermore, 1 exhibits electrochemical oxidation behavior accompanied by quenching of yellow-green emission due to the overlap of an emission band and an absorption band. The above-mentioned color changes under ambient light can also be observed by the naked eye during the mechanical, acid–base vapor and electrical stimulation. Based on the high-contrast and multicolor switching, complex 1 was successfully developed into test papers and films in the field of rapid detection of mechanical stimuli and HCl/NH₃ vapors.