Self-Assembly of Two Tubular Metalloligand-Based Palladium–Organic Cages as Hosts for Polycyclic Aromatic Hydrocarbons

Abstract

Herein we report two tubular metal−organic cages (MOCs), synthesized by the self-assembly of bidentate metalloligands with different lengths and Pd II . These two MOCs feature Pd 4 L 8 -type square tubular and Pd 3 L 6 -type triangular cage structures, respectively. Both MOCs have been fully characterized by NMR spectroscopy, mass spectrometry, and theoretical calculation. Both cages can be employed for encapsulating polycyclic aromatic hydrocarbons and show high binding affinity toward coronene.

Non‐Templated Assembly of D5h‐Symmetric Pd5L10 Rings by Precise Ligand Angle Adjustment

“…We can indeed show that the model can be used for rationalizing the nuclearity of the rings reported by others [40][41][42] and by us (Figure S47). [17,29] However, the purely geometrical model cannot be used as sole prediction tool since other factors such as the ligand flexibility, [41] deviation from the ideal square-planar Pd(II) environment, and choice of the solvent [40] affect the outcome.…”

“…In order to correlate the angle of the organic ligands with the nuclearity of the rings Pd n L 2n , we derived a mathematical model based on simple geometrical considerations (Supporting Information section 5). We can indeed show that the model can be used for rationalizing the nuclearity of the rings reported by others [40][41][42] and by us (Figure S47). [17,29] However, the purely geometrical model cannot be used as sole prediction tool since other factors such as the ligand flexibility, [41] deviation from the ideal square-planar Pd(II) environment, and choice of the solvent [40] affect the outcome.…”

“…In general, in tetranuclear Pd 4 L 8 assemblies, the metal nodes can be arranged in a cyclic, [17,41] tetrahedral [29,[59][60][61] or linear (interlocked cages) [28,62] fashion. However, the high symmetry of Pd structures reveals some striking differences: 1) In Pd 5 L 2 10 , the arrangement of the Pd(II) nodes deviates more from the ideal pentagon, in which two adjacent edges enclose an angle of 108°(Pd 5 L 1 10 : 106°-109°, Pd 5 L 2 10 : 102°-119°, Tables S2,S4).…”

Precise Post‐Synthetic Modification of Heterometal‐Organic Capsules for Selectively Encapsulating Tetrahedral Anions

“…In previous work, the self-assembly of Pd II ions with concave-shaped metalloligands yields Pd 3 L 6 or other Pd n L 2n capsules. [17] In this study, we developed a new strategy for synthesizing MOCs with unsaturated secondary coordination sites on ligands, and we investigated their structure transformations and host-guest chemistry in the solution state (Scheme 1). Herein, we report an interesting heterometallic tube-like structure, Pd 3 Cu 6 L1 6 (denoted as 1, where L1 = N, N'-(butane-1,4-diyl)bis(1-(1H-imidazol-4yl)methanimine)), [18] which can be post-synthetically modified into a Pd 3 Cu 6 L1 6 L2 2 capsule (denoted as 2) by using a tridentate anionic ligand tri(1H-imidazol-1-yl)hydroborate (L2, Scheme 1).…”

“…In previous work, the self‐assembly of Pd II ions with concave‐shaped metalloligands yields Pd 3 L 6 or other Pd n L 2n capsules [17] . In this study, we developed a new strategy for synthesizing MOCs with unsaturated secondary coordination sites on ligands, and we investigated their structure transformations and host–guest chemistry in the solution state (Scheme 1).…”