Fast and Specific Mechano- and Vapochromic Switching in Phosphorescent Estrone-Based Pt(II) Complexes.

There is an urgent demand for mechanochromic and vapochromic molecular systems that exhibit rapid switching, high specificity, and excellent repeatability. To address this demand, a series of highly phosphorescent Pt(II) complexes (emission quantum yield of up to 74.5%) have been synthesized through the conjugated incorporation of a chiral estrone fragment into a 2-phenylpyridine ligand. This functional estrone fragment likely guides the packing arrangement, enabling the complex molecules to self-assemble into dimer-like arrangement and form a porous, layered micro-nanostructure, as supported by XRD and DFT calculations. This architecture, with its large specific surface area and numerous pores, facilitates mechanochromic and vapochromic switching. The Pt1 film exhibits high-specificity recognition toward acetone. Upon exposure to acetone vapor, it shows a fast and obvious luminescence color change (red to green) with a response time of less than 0.5 s. Solvent spray technology has been utilized for high-security and multilevel-code anti-counterfeiting applications with a recovery time of 3.0 s. This approach achieves rich irreversible and reversible changes, rapid switching speeds, high specificity to acetone, and excellent repeatability. Furthermore, the inherent relationships between molecular structures and functions have been thoroughly examined, offering a promising strategy for designing multiple-stimuli-responsive switching materials.