A new photochromic-ligand-based luminescent coordination polymer as a MnO4− sensor with extremely high sensitivity and excellent selectivity

Abstract

Photochromic materials have attracted considerable attention because of their promising applications. Herein, the first dihydroanthracene-based photochromic organic ligand 9,10-bis(di(pyridine-4-yl)methylene)-9,10-dihydroanthracene (L) was successfully synthesized. Its photochromic mechanism has been elucidated. The photochromic organic molecule was first developed as a functional ligand to construct an LCP/LMOF-based sensor material {[Cd_1.5(L)(HOBA)(EtOH)(SO₄)(H₂O)]·3H₂O}_n (1) (LCP/LMOF = luminescent coordination polymer/luminescent metal–organic framework; H₂OBA = 4,4′-oxybisbenzoic acid; EtOH = ethanol). 1 exhibits a very rare 1D triple-chain architecture, and possesses good water stability and high sensing sensitivity to MnO₄⁻. More importantly, 1′ (1 after photochromism) exhibits extremely high sensitivity for detecting MnO₄⁻ in aqueous media. Its K_sv (quenching constant, 3.74 × 10⁶ M⁻¹) is nearly 28 and 8 times more than that of 1 (1.36 × 10⁵ M⁻¹) and the reported highest value (4.49 × 10⁵ M⁻¹) for MnO₄⁻ sensor materials, respectively. Moreover, 1′ has excellent MnO₄⁻ sensing selectivity and stable sensing ability at different pH. Especially, 1′ can recognize MnO₄⁻ in the presence of similar strong oxidized anions CrO₄²⁻ and Cr₂O₇²⁻. The MnO₄⁻ test paper is successfully developed as a convenient tool for practical application. The mechanisms behind the outstanding MnO₄⁻ sensing properties of 1′ were studied as well.