Variable energy transfer in one-dimensional chiral Mn/Cd-based halides and strong stereo-selective fluorescence for chiral recognition

Abstract

Low-dimensional chiral metal halides (CMHs) are promising as an industrialized platform for chiral recognition applications; however, there are hardly any luminescent CMHs with variable energy transfer between an organic ligand and an inorganic unit. Herein, an array of rare one-dimensional (1D) luminescent CMHs were engineered by screening R/S-3-aminopiperidine dihydrochloride as a chiral template, in which the chirality of the organic cation is transferred to the inorganic chain via hydrogen bonding interactions in (R/S-C₅H₁₄N₂)MCl₄·H₂O (M = Mn, Cd), abbreviated as R/S-Mn and R/S-Cd. The orange emission at 607 nm is attributed to the d–d transition ⁴T₁(G)–⁶A₁(S) of Mn²⁺ in R/S-Mn, along with an energy transfer from the organic cation to the inorganic chain. In contrast, a reverse energy transfer from the inorganic chain to the organic cation was verified in R/S-Cd, with the emission at 401 nm being attributed to the singlet self-trapped excitons (STEs) of Cd²⁺. Beyond that, we innovatively proposed that the fluorescence quenching behaviour contributes to the strong stereo-selective fluorescence responsivity for mandelic acid (MA), confirming that R/S-Mn and R/S-Cd are useful for the rapid recognition of R/S-MA. This research not only promotes the discovery of low-dimensional luminescent CMHs but also expands their applications in bio-detection and sensing.