摘要: Heterometallic 3d-4f clusters represent a promising class of multifunctional molecular materials, driven by the synergistic interactions between d- and f-electrons. Incorporating chirality into these systems further expands their potential applications, particularly in chiroptical and magneto-optical technologies. Herein, we report the successful synthesis of chiral [Ln3Co5] (Ln = Er and Y) clusters using binaphthol-based ligands. Single-crystal X-ray diffraction reveals the coexistence of two distinct Co2+ coordination geometries: six-coordinate octahedral and five-coordinate trigonal bipyramidal. Spectroscopic analyses demonstrate geometry-dependent chiroptical behavior: pentacoordinate Co2+ ions predominantly contribute to the circular dichroism (CD) features, while both geometries exhibit distinguishable signals in the magnetic circular dichroism (MCD) spectra. Notably, a pronounced magnetic dipole transition (4I15/2 → 4I13/2) from Er3+ centers is observed in the near-infrared MCD region, displaying a high g-factor of 0.0078 T-1. This work highlights the configuration- and ligand field-dependent chiroptical responses in 3d-4f systems, providing new insights for the rational design of advanced magneto-optical devices.