Manipulating Chiroptical Activities in 0D Chiral Hybrid Manganese Bromides by Solvent Molecular Engineering

0D hybrid metal halides (0D HMHs) with fully isolated inorganic units provide an ideal platform for studying the correlations between chiroptical activities and crystal structures at atomic levels. Here, through the incorporation of different solvent molecules, a series of 0D chiral manganese bromides (RR/SS-C20H28N2)3MnBr82X (X = C2H5OH, CH3OH, or H2O) are synthesized to elucidate their chiroptical properties. They show negligible circular dichroism signals of Mn absorptions due to C2v-symmetric [MnBr4]2- tetrahedra. However, they display distinct circularly polarized luminescence (CPL) signals with continuously increased luminescence asymmetry factors (glum) from 10-4 (X = C2H5OH) to 10-3 (X = H2O). The increased glum value is structurally revealed to originate from the enhancement of [MnBr4]2- tetrahedral bond-angle distortions, due to the presence of different solvent molecules. Furthermore, (RR/SS-C20H28N2)MnBr4H2O enantiomers with larger bond-angle distortions of [MnBr4]2- tetrahedra are synthesized based on hydrobromic acid-induced structural transformation of (RR/SS-C20H28N2)3MnBr82H2O enantiomers. Therefore, such (RR/SS-C20H28N2)MnBr4H2O enantiomers exhibit enhanced CPL signals with |glum| up to 1.23 x 10-2. This work provides unique insight into enhancing chiroptical activities in 0D HMH systems. Through the incorporation of different solvent molecules, chiroptical modulations of inorganic units are achieved in 0D hybrid manganese bromides, revealing that circularly polarized luminescence enhancement can be realized by regulating bond-angle distortions of [MnBr4]2- tetrahedra. By further enhancing bond angle distortion through structural transformation, |glum | values continue to amplify to 1.23 x 10-2. image