Synergistic Paramagnetic, Piezoelectric, and Chiral Optical Effects in Fe- and Mn- Hybrid Metal Halides

The integration of chirality with multiple coupled physical functionalities in a single material system is emerging as a powerful strategy for advancing next-generation photonic and electronic technologies. Intrinsically chiral hybrid metal halides, which combine molecular-level asymmetry with tunable inorganic frameworks, provide a unique platform for realizing strong chiroptical activity alongside emerging physical properties. In this context, we show that the incorporation of Fe- and Mn- centers within tetrahedral hybrid organic-inorganic metal-halide units enable the coexistence of chirality with magnetic functionality. A systematic study of two noncentrosymmetric, magnetically active hybrid metal halides, [MePPh3]FeCl4 (PFC) and [MePPh3]2MnOCl4 (PMC) show complex multifunctional behavior, where both materials display pronounced ground-state circular dichroism (CD), with dissymmetry factors gCD ≈ - 2.9 × 10-3 (PFC) and 3.1 × 10-4 (PMC), together with sizable luminescence dissymmetry factors glum ≈ - 4.6 × 10-2 and 1.6 × 10-4, respectively, indicating efficient chirality induction by the molecular cation to the inorganic framework. Under varying external magnetic fields, weak yet distinct magnetic circular dichroism (MCD) signals are observed at room temperature, resulting in enhancements of gCD by ∼ 0.58 for PFC and ∼ 0.68 for PMC, accompanied by positive spectral shifts of ∼ 2 nm and ∼ 4 nm. Simultaneously, both crystals exhibit significant piezoelectric responses, yielding impressive output voltage of Voc ≈ 1.39 V and Voc ≈ 1.95 V, upon external mechanical vibration, from the piezoelectric generator devices from PFC and PMC, respectively.