Anion-Guided Hierarchical Assembly of Heterometallic Clusters
Weiming Huang, Qingsong Yang, Wanmin Chen, Zhiping Zheng
Abstract
Anions are important as templates for the construction of many structurally sophisticated and functional supramolecular architectures. Deciphering the specific role of such templates remains a great challenge due to the unique characteristics of anions. Herein, three heterometallic Ce–Ni clusters, namely, [Ce 24 Ni 36 L 36 ( μ 4 - OAc ) 6 (OH) 52 (Cl) 8 ]Cl 6 ·110H 2 O ( Ce 24 Ni 36, OAc = acetate ion, L = N -methyliminodiacetate), [Ce 17 Ni 27 L 27 ( μ 6 - C 2 O 4 ) 6 (OH) 15 (Cl) 16 (H 2 O) 19 ](ClO 4 ) 2 Cl 6 ·45H 2 O ( Ce 17 Ni 27 ), and [Ce 21 Ni 30 L 30 ( μ 6 - C 2 O 4 ) 2 ( μ 4 - OAc )(OH) 32 (Cl) 15 (H 2 O) 14 ](ClO 4 ) 4 Cl 7 ·55H 2 O ( Ce 21 Ni 30 ), were obtained and structurally characterized; the formation of these cage-like clusters was assisted, respectively, by acetate, oxalate, and a combination of the two as templates. Structural analyses generate key information on the anion-directed hierarchical assembly, starting from a primary building block of {CeNi 3 } to two anion-specific secondary building blocks (SBUs)─the tetragonal {Ce 4 Ni 8 ( OAc )} and the pentagonal {Ce 5 Ni 9 ( C 2 O 4 )}. Further assembly steps are guided by these curved SBUs, affording a truncated octahedral Ce 24 Ni 36 and a lantern-like Ce 17 Ni 27, with acetate and oxalate being the sole template, respectively. The combined use of acetate and oxalate produced Ce 21 Ni 30, a cluster with an unprecedented structure viewable as a hybrid of a truncated octahedron and a dodecahedron.