Interface-Induced Symmetry-Breaking Processes Behind Intrinsic Chirality in Lead Halide Metal–Ligand Complexes and Perovskite Nanoclusters

Here, we investigated the origin of chirality in PbBr₂-DMF metal-ligand complexes (MLCs) and their evolution into larger chiral nanoclusters. Utilizing a combination of UV-vis electronic absorption and circular dichroism (CD) spectroscopy, we identified chiral MLCs at 283 and 310 nm, which were assigned as [PbBr₂(DMF)₄] and [PbBr₃(DMF)₃]^-1. Upon the addition of methylammonium bromide (MABr) and injection into toluene with oleic acid/oleylamine ligands, new bands appeared at ∼370, 395, and 430 nm. These are assigned to multi-Pb MLCs, molecular clusters (MCs), and perovskite nanoclusters (PNCs), respectively. Raman spectra indicate PbBr₂ dissolution and Pb-DMF coordination based on the shift of PbBr₂ phonon modes alongside the appearance of new Pb-Br stretches and solvation-induced low-frequency modes associated with Pb-DMF bonding. Preliminary density functional theory (DFT) calculations also support both Pb-O and Pb-N binding, as the difference in relative energies between O- and N-bound MLC configurations is comparable to room-temperature thermal motion. Our findings demonstrate that chirality can originate directly from asymmetric solvation of Pb²⁺ at the solid-liquid interface and propagate through hierarchical growth into larger assemblies, providing a vital foundation for understanding the emergence of chirality in perovskite nanomaterials.