High-Nuclearity Chiral 3d-4f Heterometallic Clusters Ln6Cu24 and Ln6Cu12

Based on the anion template and chiral ligand inducting role, two series of high-nuclearity 3 d -4 f heterometallic clusters with formulas [NO 3 @Ln 6 Cu 24 (μ 3 -OH) 30 (μ 2 -OH) 3 (OAc) 6 ( R / S -L) 12 (H 2 O) 24 ](NO 3 ) 14 · x (H 2 O) (Ln = Dy, x = 30 for 1a ( R -L) and 1b ( S -L); Ln = Tb, x = 40 for 2a ( R -L) and 2b ( S -L)) and (Et 3 NH) 4 [Ln 6 Cu 12 (μ 3 -OH) 14 (μ 2 -Cl) 6 Cl 12 ( R / S -L) 12 ]Cl 2 · x (H 2 O) (Ln = Dy, x = 28 for 3a ( R -L) and 3b ( S -L); Ln = Tb, x = 33 for 4a ( R -L) and 4b ( S -L); HL = ( R / S )-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid), have been synthesized and characterized. Structural analysis reveals that the metal skeleton of compounds 1 and 2 display a Ln 6 Cu 12 octahedral inner core encapsulated by six outer Cu 2 units. In the Ln 6 Cu 12 octahedron, 6 Ln 3+ ions located at the six vertices and 12 inner Cu 2+ ions located at the 12 edges of octahedron, and one NO 3 – locates in the center of the octahedron. The metal core of compounds 3 and 4 can be viewed as a Ln 6 octahedron encapsulated by six Cu 2 units. It is interesting that the different inorganic anions involved in the reaction result in the difference in the structures of 1 to 2 and 3 to 4 . Circular dichroism spectra of 1 – 4 display obvious mirror symmetry effect at 600–800 nm of d–d transition of Cu 2+, suggesting that the chirality transferred from chiral R - and S -ligand to Cu 2+ ions in this system. Notably, the CD peak at the Cu 2+ d–d transition position of Ln 6 Cu 12 cluster is obviously blue-shifted compared with that of Ln 6 Cu 24 due to the different coordinated environments of Cu 2+ . Magnetic studies indicate that 1a and 2a show weak ferromagnetic interactions, while 3a and 4a display antiferromagnetic interactions.