Assembly of Homochiral Magneto-Optical Dy₆ Triangular Clusters by Fixing Carbon Dioxide in the Air

A new hydrazone Schiff base bridging ligand (H₂L_Schiff (E)-N′-((1-hydroxynaphthalen-2-yl)methylene)pyrazine-2-carbohydrazide) and L/D-proline were used to construct a pair of homochiral Dy₆ cluster complexes, [Dy₆(CO₃)(L-Pro)₆(L_Schiff)₄(HL_Schiff)₂]·5DMA·2H₂O (L-1, L-HPro = L-proline; DMA = N,N-dimethylacetamide) and [Dy₆(CO₃)(D-Pro)₆(L_Schiff)₄(HL_Schiff)₂]·5DMA·2H₂O (D-1, D-HPro = D-proline), which show a novel triangular Dy₆ topology. Notably, the fixation of CO₂ in the air formed a carbonato central bridge, playing a key role in assembling L-1/D-1. Magnetic measurements revealed that L-1/D-1 displays intramolecular ferromagnetic coupling and magnetic relaxation behaviours. Furthermore, L-1/D-1 shows a distinct magneto-optical Faraday effect and has a second harmonic generation (SHG) response (1.0 × KDP) at room temperature. The results show that the immobilization of CO₂ provides a novel pathway for homochiral multifunctional 4f cluster complexes.