H/F substitution drives luminescence modulation and piezoelectric encryption of Mn-based halides

H/F substitution drives the coordination reconstruction of Mn 2+ in hybrid chlorides. • Isolated [MnCl 4 ] 2- tetrahedra change to face-sharing [Mn 2 Cl 9 ] 5- units. • The four-to-six coordination change enables green-to-red emission centered at 634 nm. • The fluorinated non-centrosymmetric crystal exhibits phase-transition and piezoelectric responses. Regulation of the Mn 2+ coordination environment is an effective approach for tuning the luminescence of Mn-based hybrid halides. However, the use of H/F substitution on organic cations to regulate the coordination environment of Mn 2+ and thereby tune the emission color remains rarely explored. In this work, H/F substitution was introduced into the piperidinium cation, driving the transformation of Mn-Cl coordination units from four-coordinate to six-coordinate structures and yielding the zero-dimensional hybrid chloride (4-F-Hpip) 5 [Mn 2 Cl 9 ]. This material crystallizes in the chiral non-centrosymmetric P 4 1 2 1 2 space group and contains face-sharing dinuclear [Mn 2 Cl 9 ] 5- units with octahedrally coordinated Mn 2+ . The resulting ligand-field change gives rise to broad red emission centered at 634 nm, while the compound also exhibits a reversible phase transition. In addition, a flexible PBAT composite film containing 10 wt% (4-F-Hpip) 5 [Mn 2 Cl 9 ] generates an open-circuit voltage of approximately 4.9 V. Its luminescent and piezoelectric responses were further integrated into a conceptual dual-input information encryption scheme. This work establishes H/F substitution as an effective cation engineering strategy for regulating Mn 2+ coordination and luminescence in hybrid manganese halides. Download: Download high-res image (198KB) Download: Download full-size image