Tuning the Size and Geometry of Heteroleptic Coordination Cages by Varying the Ligand Bent Angle

Abstract

Spherical assemblies of the type [Pd n L 2n ] 2n + can be obtained from Pd II salts and curved N-donor ligands, L. It is well established that the bent angle, α, of the ligand is a decisive factor in the self-assembly process, with larger angles leading to complexes with a higher nuclearity, n. Herein, we report heteroleptic coordination cages of the type [Pd n L n L' n ] 2n + , for which a similar correlation between the ligand bent angle and the nuclearity is observed. Tetranuclear cages were obtained by combining [Pd(CH 3 CN) 4 ](BF 4 ) 2 with 1,3-di(pyridin-3-yl)benzene and ligands featuring a bent angle of α = 120°. The use of a dipyridyl ligand with α = 149°led to the formation of a hexanuclear complex with a trigonal prismatic geometry; for linear ligands, octanuclear assemblies of the type [Pd 8 L 8 L' 8 ] 16 + were obtained. The predictable formation of heteroleptic Pd II cages from 1,3-di(pyridin-3-yl) benzene and different dipyridyl ligands is evidence that there are entire classes of heteroleptic cage structures that are privileged from a thermodynamic point of view.

Unlocking the computational design of metal–organic cages

“…This work shows that the bite angle rule applies generally and has led to the robust development of large homoleptic and heteroleptic MOCs with multiple metal species. 29,[41][42][43][44][45] Even with these design rules in hand, deviations from expectation occur. 12,36 This is especially true when ligands deviate, even slightly, from the rigid approximation.…”

Directing metallo-supramolecular assembly through complementarity

“…3c). There have been multiple examples of the successful use of this strategy from the Clever group, 21,22 the Severin group, [23][24][25] the Chand group 26,27 and a recent report from ourselves. 28 Similar results have been reported with low symmetry ligands in the formation of homoleptic but reduced symmetry cages, by the groups of Lewis, [29][30][31] Yuasa 32 and from Zhang, Wang and co-workers.…”

Self-Assembly of a Pd4Cu8L8 Cage for Epoxidation of Styrene and Its Derivatives

“… , Cage 1 can act as an efficient heterogeneous catalyst for the epoxidation of styrene and its derivatives by using TBHP as an oxidizing agent. Bent bis-monodentate pyridyl or imidazolyl ligands bind with Pd 2+ ions to form Pd n L 2 n cages with varied structures, which have been proven to be an excellent strategy in making MOCs. − However, no such similar heterometallic Pd n (CuL) 2 n cage based on a CuL metalloligand has thus far been reported.…”

“…The Pd II −N bond distances are in the range of 2.005−2.018 Å, which is similar to the bond distances in reported Pd 4 L 8 cages. 32,35,39,41,42 As shown in Figure 1d, cage 1 can also be treated as a cubic solid, when the Cu II ions act as the nodes and Pd II ions act as the face centers. As shown in Figure S6a, two types of channels are observed by extended crystal packing of cage molecules, and the sizes are approximately 10.25 × 10.15 Å and 10.23 × 14.74 Å, respectively.…”